Genetics
Genetics
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2
Experimental genetics
began in an abbey garden
 The modern science of genetics
began in the 1860s when a monk
named Gregor Mandel deduced
the fundamental principles of
genetics by breeding garden
peas.
 Mendel lived and worked in an
abbey in Austria.
 Strongly influenced by his study of
physics, mathematics, and
chemistry at the University of
Vienna, his research was both
experimentally and
mathematically rigorous, and
these qualities were largely
responsible for his success.
Mendel
 In a paper published in 1866,
Mendel correctly argued that
parents pass on to their offspring
discrete hereditary factors.
 He stressed that these hereditary
factors (today called genes)
retained their individuality
generation after generation.
 In other words genes are like
marbles of different colors: just as
marbles retain their colors
permanently and do not blend, no
matter how they are mixed, genes
permanently retain their identities.
Mendel
 Mendel probably chose to study garden
peas because he was familiar with them
from his rural upbringing, they were easy
to grow, and they came in many readily
distinguishable varieties.
 Perhaps most importantly, Mendel was
able to exercise strict control over pea
plant matings.
Mendel
 The petals of the pea
flower almost
completely enclose
the reproductive
organs.
 Consequently, pea
plants usually selffertilize in nature.
That is, pollen grains
land on the egg of
the same flower.
Mendel
 Mendel could ensure
self-fertilization by
covering a flower with a
small bag so that no
pollen from another plant
could reach the egg.
 When he wanted crossfertilization (fertilization
of one plant by pollen
from a different plant), he
used a particular method
so that he could be sure
of the heritage of the new
plants.
Mendel
 Mendel worked with his
plants until he was sure
he had true breeding
varieties-- that is,
varieties for which self
fertilization produced
offspring all identical to
the parent. In other
words, a “pure-bred”
plant).
 For instance, he
identified a purple
flowered variety that
produced offspring plants
that all had purple
flowers.
Hybridization
 Now Mendel was ready to ask what would
happen when he crossed his different true
breeding varieties with each other.
 For example, what offspring would result if
plants with purple flowers and plants with white
flowers were cross fertilized?
 In the language of the plant and animal
breeders and geneticists, the offspring of two
different varieties are called hybrids, and the
cross-fertilization itself is referred to as
hybridization, or simply a cross.
Hybridization
 The true breeding
parental plants are called
the P generation and
their hybrid offspring are
the F1 generation.
 The offspring of F1
plants are known as the
F2 generation.
HEREDITARY PHYSICAL
CHARACTERISTICS
 Genotype and Phenotype
 Genotype means the type of genes a person
has, or their genetic make-up.
 Genes, the units of heredity that control the specific
characteristics of an individual, are arranged in a
linear fashion along the chromosomes.
 Alleles are a pair of genes on a pair of
chromosomes that affect the same trait. For
instance, both chromosomes have an allele for eye
color, both have an allele for skin color, etc.
11
HEREDITARY PHYSICAL
CHARACTERISTICS
 Those genes that affect the same trait are
called alleles.
 A dominant allele is given a capital letter, and a
recessive allele is given the same letter in lower
case.
 For instance, having an earlobe that is
unattached to the face is a dominant trait, so we
can call it E.
 An attached earlobe would then be called e.
Alleles
 Alleles occur in pairs; just as one pair of
each type of chromosome is inherited
from each parent, so too each pair of
alleles are inherited from each parent.
 The allele which is traditionally
indicated by an uppercase (capital)
letter is the dominant trait.
 The allele which is traditionally
indicated by a lowercase (small) letter
is the recessive trait.
Homozygous
 If a sperm cell has e and the egg cell has e, the




offspring must have ee.
That is called homozygous (pure) recessive.
That means the person would have an attached
earlobe.
If a sperm cell has E and the egg cell has E, the
offspring must have EE.
This is called homozygous (pure) dominant.
That means the person would have an
unattached earlobe.
Homozygous
 The term for “pure” is homo. It refers to
something being the same.
 In the old days, you had to shake up milk
because the cream would rise to the top.
Nowadays, people want less fat, so the cream
is removed before you get it; this is called
homogenized milk.
 A homogenized mixture is one that is the same
throughout, and requires no periodic mixing.
 Therefore, when the allele pairs are either EE
or ee, they are homozygous.
Heterozygous
 The opposite of homo is “hetero”, so an
allele pair that is “Ee” is heterozygous.
 If one of the sex cells has E and the
other sex cell has e, what will the
offspring have? Ee.
 What type of earlobe will they have?
Unattached. Why? Because the
dominant trait is stronger, so if it is
present at all, it will manifest.
Phenotype
 The physical appearance of a person
is called the phenotype.
 A person with Ee will therefore be
called a heterozygous genotype, with
an unattached earlobe phenotype.
Sample Problems
 What earlobe alleles will a person
have who is homozygous recessive?
ee
 What earlobe alleles will a person
have who is homozygous dominant?
EE
 What earlobe alleles will a person
have who is heterozygous? Ee
Figuring the Odds
 If one of the parents is homozygous dominant
(EE), the chances of their having a child with
unattached earlobes is 100 %, because this
parent has only a dominant allele (E) to pass on
to the offspring.
 On the other hand, if both parents are
homozygous recessive (ee), there is a 100%
chance that each of their children will have
attached earlobes.
Figuring the Odds
 However, if both parents are
heterozygous, then what are the
chances that their child will have
unattached or attached earlobes?
 To solve a problem of this type, it is
customary first make a table (Punnet
Square) of the genotype of the parents
and their possible gametes.
Punnet Square
E
e
E
EE
Ee
e
Ee
ee
Figuring the Odds
 That means that when Harry meets
Sally, their child has a 25% chance (1:3)
of being ee, and 25% chance of being
EE, and 50% chance (1:1) of being Ee.
 But that’s just the genotype. What about
the phenotype (what will the child look
like)?
 There is a 75% chance (3:1) of having
an unattached earlobe (Ee or EE).
 There is a 25% chance (1:3) of having
an attached earlobes (ee).
Sample Test Questions
 In crossing a heterozygous parent
and a homozygous recessive parent,
what is the percent chances that an
offspring will receive a dominant
allele?
 Answer = 50%
Sample Test Questions
 What is the ratio of the phenotype for
crossing two heterozygous parents
for ear lobe attachment?
3:1
 What is the ratio of the genotype for
crossing two heterozygous parents
for ear lobe attachment?
1:2:1
Sample Test Questions
 Free earlobes (E) are dominant over
attached earlobes (e).
 If two people with homozygous
attached earlobes mate, what will be
the phenotype of their offspring?
 All attached earlobes
Sample Test Questions
 What is the ratio for crossing a
heterozygous parent for ear lobe
attachment and a homozygous
recessive parent:
 1:1
Sample Test Questions
 In crossing two heterozygous
parents, what are the chances (in
percent) for a pure recessive
offspring?
 25%
 For calculating eye color, let’s say the
father has brown eyes (BB) and the
mother has blue eyes (bb).
 Use the Punnet Square to calculate the
odds of what the child will look like. The
father’s alleles are written in the vertical
column and the mother’s on the
horizontal.
33
 When we fill in the squares, we see that
all of the children will be heterozygous
(Bb) genotype. What color eyes will the
babies all have? Brown. Therefore, the
phenotype of all the children will be
“brown-eyed”.
34
 What if the father had brown eyes but his
genotype was Bb instead of BB and they
had 4 children?
 Two of their children would have the genotype Bb
(heterozygous for brown eyes), and two of their children
would have the genotype bb (homozygous for blue eyes).
Therefore, there is a 50% chance that each child would
have the phenotype of brown eyes and 50% chance that
each child will have the phenotype of blue eyes.
b
35
 What if both parents were heterozygous?
 One child would have the genotype BB, two would have the
genotype Bb, and one would have the genotype bb. That
means that three out of four children would have brown
eyes and one would have blue eyes. Therefore, there is a
75% chance their child will have brown eyes and 25%
chance they will have blue eyes.
 Another way to write this is that there is a 3:1 ratio of brown
eyed to blue eyed children.
 That would describe the phenotype (appearance), but the
genotype would be written as
 1:2:1
B
b
36
PERSONAL PHENOTYPE
ANALYSIS
 Everyone clasp your hands together and
hold them in the air: which thumb is on
top? “Thumb crossing” is a genetic
phenotype.
37
PERSONAL PHENOTYPE
ANALYSIS

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




HANDEDNESS: Do you write with your right or left hand? Left handedness is
recessive.
MID-DIGITAL HAIR: do you have hair on the middle segment of your fingers and
toes?
HITCHHIKER’S THUMB: Make a fist with your thumb extended. Is there almost a
90° angel between the first two joints of your thumb? It is a recessive trait.
THE LENGTH OF THE INDEX FINGER in comparison to your ring finger is
influenced by your sex. A short index finger is dominant in males and recessive in
females.
COLOR BLINDNESS: Look through the color-blindness testing books on the
demonstration table. Can you distinguish the numbers and patterns on each
page? About 8% of American males and 0.4% females are recessive for red and
green color blindness.
PTC TASTERS: If you place a PTC test paper on your tongue for a minute, to
some people it will taste bitter. Others do not taste anything. People who taste
bitterness also tend to dislike broccoli and Brussels sprouts.
SODIUM BENZOATE: This is a food preservative; taste this paper in the same
way. Does it taste salty, sweet, sour, bitter, or not at all to you?
NUTRASWEET: Does this taste sweet or bitter to you?
38
39
MAKE A BABY
INSTRUCTIONS
 Now everyone is going to make a baby. Ready? Set? GO! (Just
kidding)
 Use the Make a Baby Handout.
 Each of you should take a penny and work in pairs; it doesn’t matter
if your partner is the opposite sex. There is a Data Table towards the
end of the handout that you can record the characteristics of your
baby. Record your names as parents on this data sheet. Then
determine the sex of the child by flipping the coin. Give your child a
name and record it. Every time you flip the coin, heads means a
dominant trait, so write it down as a capital letter. Tails means it is a
recessive trait, so write it down as a small letter. Each parent
donates one gene (one letter) so the child has two letters. Then
check the instructions to see what the baby’s letter combination
represents.
40
Getting Started
 1. FACE SHAPE
 Flip your coin; if it’s heads, write down a capital
R, because you have donated a dominant
characteristic to your baby. If it was tails, write
down a small “r” because the gene you gave
your baby is recessive. Then your partner flips
the coin for face shape. If the two flips result in
Rr, or rr, then your baby has a round face. If the
two flips were RR, your baby has a square face.
Record this in your data table.
 Complete the rest of the traits to see what your
baby looks like!
41
REVIEW OF GENETICS
 Our nucleus contains 46 chromosomes (23 pairs). A chromosome is






a double-stranded string of DNA. Stretched out, it is six feet long!
DNA is made of a string of molecules called nucleic acids. There are
only 4 different nucleic acids: Adenine (A), Thymine (T), Guanine
(G), and Cytosine (C).
Each A, T, G, or C on one strand of DNA is paired to its counterpart
on the other strand of DNA.
Adenine (A) only pairs with Thymine (T), and Guanine (G) only pairs
with Cytosine (C).
When they pair up, they are called base pairs. There are about 250
million base pairs of nucleic acids on one chromosome!
The double strand of DNA looks like a ladder. It is then twisted into a
shape called a helix.
42
Therefore, DNA is a double-stranded helix.
43
 When the body needs a particular protein, the double-stranded DNA
helix unwinds, just in the segment that contains the nucleic acid
sequence (called a GENE) for that protein. The DNA strand that is
copied is called the sense strand (or + strand), and the other strand is
called the antisense strand (or – strand).
 The gene is copied in the nucleus and the copy is taken to the
cytoplasm, then taken to a ribosome, which reads the nucleic acid
sequence.
 Every three nucleic acids code for one particular amino acid. These
amino acids are then linked in the proper order in the ribosome, and
the protein is made.
 When a person has a genetic defect, it is because the nucleic acids
are not in the exact right order. There may be one nucleic acid
substituted for another. There may be a new nucleic acid inserted.
There may be a nucleic acid deleted. These things will displace the
rest of the nucleic acid sequence. Sometimes, just one amino acid in
the wrong order will cause death in a person before they are born.
44
 A gene is a particular sequence of nucleic acids
on the DNA strand of the chromosome. The
function of the genes on the DNA is to tell RNA
to tell a ribosome how to make a particular
protein. Proteins carry out most of the functions
of the body.
 TRANSCRIPTION is the process of DNA
creates the RNA strand in the nucleus. The
type of RNA it makes is called mRNA
(messenger RNA). The gene on the DNA is
like my hand. I want to duplicate my hand, so I
make a clay mold of it. The clay mold is the
messenger RNA molecule.
 This occurs in the nucleus.
 The mRNA then exits the nucleus through 45
a pore and goes to the cytoplasm.
 TRANSLATION is the process of mRNA is read
by a ribosome, telling the ribosome what order
to put the amino acids in. The amino acids
become the protein. Therefore, translation is
characterized by PROTEIN SYNTHESIS.
 This occurs in the cytoplasm.
 During translation, the mRNA (clay mold of
my hand) has already left the nucleus and
is now in the cytoplasm. The RNA presents
its “hand imprint” to the ribosome. The
ribosome fills the hand imprint with
“plaster” to make a positive cast, or a
duplicate of the original gene.
46
47
 When the ribosome reads the copy of the gene (the
nucleic acid sequence) that was made in the cytoplasm,
every group of three nucleic acids is called a CODON.
Each codon codes for one amino acid.
 For example, if the first three nucleic acids are G, C, T,
when you check that code in a manual, you find that
means the first amino acid is Alanine. If the next three
nucleic acids are C, C, G, that codes for Proline.
Therefore, the ribosome links alanine to proline, and so
on, until the entire amino acid sequence is finished.
 This new protein is placed in an envelope for protection,
and dumped into the endoplasmic reticulum. During its
journey in the RER and then in the Golgi complex,
protective molecular groups are placed around the
delicate ends and side groups of the protein. After that,
it is ready to start functioning.
48
 TRANSCRIPTION VIDEO
 TRANSCRIPTION WEBSITE
 TRANSLATION VIDEO
 TRANSLATION WEBSITE
 DECODING A GENE
 DNA KIT PROJECT (Handout: Do page
one now)
49
Amino Acids build proteins
Building blocks of protein, containing an amino
group and a carboxyl group
Amino acid structure: central C; amino group,
acid group, and variable group
a) AMINO ACIDS are MONOMERS (building
blocks) of protein. They are tiny carbon molecules,
made of just a carbon atom and a few other atoms.
There are only 22 standard types of amino acids in the
human body (20 of them are involved in making
proteins). Nine of these are essential amino acids,
meaning that we have to get them in the diet. We can
synthesize the others.
Amino acids are like beads on a necklace. Each bead is an
amino acid, and the whole necklace is the protein. A
bunch of the same types of necklaces (proteins) woven
together makes up our tissues.
51
Amino Acids
Essential
Histidine
Leucine
Isoleucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
Nonessential
Alanine
Arginine
Asparagine
Aspartic acid
Cysteine
Glutamic acid
Glutamine
Glycine
Ornithine
Proline
Selenocysteine
Serine
Tyrosine
52
Mutations of Genes
 Mutation – change in the nucleotide base
sequence of a genome; rare
 Not all mutations change the phenotype
(appearance)
 Two classes of mutations

1. Base substitution


53
eg point mutation
 GTTCAAG - (normal)
 ATTCAAG - mutant (abnormal)
Silent mutation
 No change in amino acid sequence
Mutations of Genes
 Missense mutation

New amino acid


ALA-PHE-LEU-TRY-STOP
PHE-PHE-LEU-TRY-STOP
 Non-sense mutation – a stop codon is
inserted into protein sequence


54
Truncated protein
ALA-PHE-STOP-TRY-STOP
Mutations
 2. Frameshift mutation


Insertion or deletion of one or more bases
Original sequence: ATG CCA GGT AAG
 Insertion:
ATT GCC AGG TAA G
 Deletion: ATC CAG GTA AG_

55
If it happens at the end of a gene it may not
be as bad
Effects of Mutation
56
Figure 7.20
Genetic Code
57
Figure 7.9
DNA Handout: do pages 3-4 now
 Missense mutation eg. sickle cell

results in a codon that codes for a different amino
acid. The resulting protein may be nonfunctional
 Nonsense mutation eg Cystic fibrosis

Stop codon is inserted, truncated protein
 Frameshift insertion eg. Tay-Sachs disease
 Frame shift deletion CCR5

58
CCR5 is our cell membrane receptor that the HIV
virus uses to attack. People with this genetic
mutation are immune to many strains of the AIDS
virus.
Causes of mutations
 Spontaneous mutations
 Happens
during replication
More often in prokaryotes than
eukaryotes.
Eukaryotes have better repair
mechanisms.
59
Mutagens
 Radiation


Ionizing radiation (x-rays) – induces breaks
in chromosomes
Nonionizing radiation (UV light) – induces
thymine dimers
 Chemical Mutagens
 Nucleotide analogs – disrupt DNA and
RNA replication and cause point mutations



60
Eg. 5-bromouracil pairs with guanine
Caffeine not a strong mutagen – but it does
effect fetal development
Alkylating agents- used for cancer treatment
DNA Repair
Figure 7.2461
DNA Repair
Figure 7.2462
Radiation gigantism from the
Fukushima disaster

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gation_id=288381481237582
Identifying Mutants, Mutagens,
and Carcinogens
 DNA DAMAGE VIDEO
 TUMOR GROWTH VIDEO
 Mutants – descendents of cell that does not
successfully repair a mutation
 Wild types – mutant cells normally found in
nature
 Methods to recognize mutants

Positive selection


Negative (indirect) selection

64
Survival of the fittest
selective removal of rare alleles that are deleterious.
Genetic Recombination and
Transfer
 Recombination and transfer of genes occurs during exchange of DNA
segments with those of another DNA segment
 Recombinants – cells with DNA molecules that contain new nucleotide
sequences
 Vertical gene transfer – organisms replicate their genomes and provide
copies to descendants
 Horizontal gene transfer – donor contributes part of genome to
recipient; three types
 Transformation
 Transduction
 Bacterial Conjugation
65
Transformation Experiments
 The transforming agent in the experiment
was DNA; became the evidence that
DNA is genetic material
 Cells that take up DNA are competent.
66
Griffith’s Transformation Experiment
67
Figure 7.29
Transduction
 Transduction is the process by which DNA is transferred
from one bacterium to another by a virus.
 When bacteriophages (viruses that infect bacteria) infect
a bacterial cell, their normal mode of reproduction is to
harness the replication machinery of the host bacterial
cell to make numerous virions, or complete viral particles,
including the viral DNA or RNA and the protein coat.
 Transduction explains how antibiotic drugs become
ineffective due to the transfer of resistant genes between
bacteria.
 In addition, transduction experiments attempt to cure
diseases such as Muscular Dystrophy.
68
Generalized Transduction
69
Figure 7.30
Bacterial Conjugation
Figure 7.3170
Bacterial Conjugation
Figure 7.3171
VIDEOS
 CELL SIGNALS VIDEO (13 mins)
 STEM CELLS VIDEO
72
French police on hunt for serial rapist
stumped by identical twin suspects
 Police are holding both brothers while they run
extensive genetic tests to try to distinguish
between the two. The complicated tests could
cost more than $1 million.
 The environment can change our DNA too. We
all build up mutations in our DNA over time. Our
DNA also changes in response to things like
sunlight or the food we eat.
 These changes are pretty rare. Everyone has
about 100 new mutations in their DNA. Sounds
like a lot but spread out over 3 billion base pairs,
that is quite a needle in a haystack.
 Also, all of the changes aren't in all of your cells - not all of your cells have the same DNA
sequence! If a DNA mistake happens late in our
development, then only a few cells will have that
mutation. If a mistake happens early, then more
cells will have the DNA change but still not all of
them.
 The differences between identical twins increase
as they age, because environmentally triggered
changes accumulate.
Why do identical twins have
different fingerprints?
 While you were growing inside of your
mother, you touched the amniotic sac.
 When you touched it during weeks 6-13,
the patterns of your fingerprints were
changed.
 This is why identical twins have different
fingerprints.
GENETIC DISORDERS
 1. Chromosome Disorders
 2. Sex Chromosomal Disorders
 3. Dominant Disorders (only one dominate
allele needs to be present)
 4. Homozygous Recessive Disorders
(both parents must have rr alleles)
 5. Incompletely Dominant Traits
 6. Sex-Linked Traits
 7. Sex-Influenced Traits
77
Down Syndrome
 Down syndrome is also called trisomy 21
because the person’s chromosome number 21
has three chromosomes joined together instead
of just two.
 The chances of a woman having a Down
syndrome child increase rapidly with age,
starting at about age 40.
 The frequency of Down syndrome is 1/ 800
births for mothers under 40 years of age, but
women over 40 are 10 times more likely to have
a Down syndrome child.
Down Syndrome
 Characteristics of Down
syndrome include a short
stature; an eyelid fold; stubby
fingers; a wide gap between the
first and second toes; a large,
fissured tongue; a round head; a
palm crease (the so-called
simian line), and mental
retardation, which can
sometimes be severe.
Down Syndrome
Their
personalities
are usually
cheerful,
good-natured,
and pleasant
throughout
their lives.
Down Syndrome
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Amniocentesis
 Removing fluid and cells from the amniotic sac
surrounding the fetus, followed by karyotyping
can detect a Down syndrome child.
 Scientists have located genes most likely
responsible for the increased tendency toward
leukemia, cataracts, accelerated rate of aging,
and mental retardation.
 One day it might be possible to control the
expression of that gene even before birth so
that at least this symptom of Down syndrome
does not appear.
Amniocentesis
Cri du Chat Syndrome
(“cat’s cry”)
 Cri du Chat Syndrome (“cat’s cry”)
 This is caused by one missing segment of
chromosome 5 and occurs in 1/ 50,000 live
births. An infant with this syndrome has a
moon face, small head, and a cry that
sounds like the meow of a cat because
of a malformed larynx. An older child has
an eyelid fold and misshapen ears that are
placed low on the head. Severe mental
retardation becomes evident as the child
matures.
84
Cri Du Chat Syndrome
85
Sex Chromosomal Disorders
 All of the cells in our body have all of our chromosomes
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in the nucleus except for the egg and the sperm.
Each of these has all of our chromosomes in the nucleus,
except there is only one of the two sex chromosomes.
Since women are XX, all of her egg cells are X, but
since males are XY, a sperm can bear an X or a Y.
Therefore, the sex of the newborn child is determined
by the father.
If a Y- bearing sperm fertilizes the egg, then the XY
combination results in a male.
On the other hand, if an X-bearing sperm fertilizes the
egg, the XX combination results in a female.
88
Chromosomal Disorders
 All factors being equal, there is a 50%
chance of having a girl or a boy.
 If a couple has 10 children and they are
all boys, what is the chance that an
eleventh child is going to be a boy?
 Interestingly, the death rate among
males is higher than for females.
 By age 85, there are twice as many
females as males.
Jacob syndrome
 occurs in 1/ 1,000 births.
 These XYY (an extra male chromosome) males
are usually taller than average, suffer from
persistent acne, and tend to have speech and
reading problems.
 At one time, it was suggested that these men
were likely to be criminally aggressive, but it
has since been shown that the incidence of
such behavior among them may be no greater
than among XY males.
Jacob Syndrome: XYY
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Klinefelter syndrome
 occurs in 1/ 1,500 births.
 These males with XXY (an extra female
chromosome) and they are sterile.
 They are males with some female
characteristics.
 The testes are underdeveloped, they have
some breast development, and there is no
facial hair.
 They are usually slow to learn but not mentally
retarded.
Klinefelter
syndrome
Klinefelter syndrome: XXY
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Triple-X syndrome
 occurs in 1/ 1,500 births.
 These are females with an extra female
chromosome: XXX.
 You might think they are especially feminine,
but this is not the case.
 Most have no physical abnormalities except
that they may have learning disabilities,
menstrual irregularities, including early onset of
menopause.
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Triple-X syndrome
Turner syndrome
 occurs in 1/ 6,000 births.
 The individual is XO, meaning one of the sex
chromosomes is missing.
 These are females and have a short, broad
chest, and webbed neck.
 The ovaries and uterus are nonfunctional.
Turner females do not undergo puberty or
menstruate, and there is a lack of breast
development.
 They are usually of normal intelligence and can
lead fairly normal lives, but they are infertile
even if they receive hormone supplements.
Turner’s Syndrome
Turner syndrome: XO
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Dominant Disorders:
Neurofibromatosis
 Used to be known as Elephant Man disease, this is one
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of the most common genetic disorders.
It affects roughly 1/ 3,000 people.
It is seen equally in every racial and ethnic group
throughout the world.
At birth or later, the affected individual may have six or
more “coffee with milk” colored spots (known as
cafe-au-lait) on the skin.
Such spots may increase in size and number and may
get darker.
Small benign tumors (lumps) called neurofibromas may
occur under the skin or in various organs.
Neurofibromatosis
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Neurofibromatosis
Neurofibromatosis
 In most cases, symptoms are mild, and patients

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
live a normal life.
In some cases, however, the effects are severe.
Skeletal deformities, including a large head, are
seen, and eye and ear tumors can lead to
blindness and hearing loss.
Many children with neurofibromatosis have
learning disabilities and are hyperactive.
The abnormal gene is on chromosome 17.
Dominant Disorders
 Huntington Disease
 This affects 1/ 20,000 people.
 It is a dominant neurological disorder that leads to
progressive degeneration of brain cells, which causes
severe muscle spasms and personality disorders.
 Most people appear normal until they are of middle age
and have already had children who might also be
stricken.
 There is no effective treatment, and death often comes
ten to fifteen years after the onset of symptoms.
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Huntington’s Disease
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Homozygous Recessive
Disorders: Tay - Sachs disease
 This disease usually occurs among Jewish people.
 At first, it is not apparent that a baby has Tay-Sachs
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disease.
However, development begins to slow down between
four months and eight months of age, and neurological
impairment and psychomotor difficulties then become
apparent.
The child gradually becomes blind and helpless,
develops uncontrollable seizures, and eventually
becomes paralyzed.
There is no treatment or cure for Tay-Sachs disease, and
most affected individuals die by the age of three or four.
It is caused by a genetic enzyme deficiency.
Tay - Sachs disease
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Cystic Fibrosis
 This is the most common lethal genetic
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disease among Caucasians in the United
States.
About 1 in 20 Caucasians is a carrier, and
about 1/ 2,500 births have the disorder.
In these children, the mucus in the bronchial
tubes is particularly thick and interferes with
breathing, and the lungs get infected
frequently.
New treatments have raised the average life
expectancy to 28 years of age.
The cystic fibrosis gene is located on
chromosome 7.
Cystic Fibrosis
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Phenylketonuria (PKU)
 This occurs in 1 / 5,000 births, so it is not as frequent as
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the disorders previously discussed, however, PKU is
tested for in routine blood screenings of all newborns in
the United States.
This is the disease that offspring of first cousins are
more likely to get.
PKU people lack an enzyme that is needed to break
down an amino acid (phenylalanine), and so the amino
acid accumulates in the urine.
These people have to have a special diet that does not
contain that amino acid.
If they get too much of it, they will get neurological
problems and mental retardation.
That’s why nutrition labels have to warn when they
contain phenylalanine.
PKU
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Incompletely Dominant Traits
 Incomplete dominance is exhibited when
there is an intermediate phenotype.
 These people can be carriers of a
disorder without being sick themselves.
 Their children may have the disorder, or
they also may be carriers.
 When they are carriers, they are said to
have the “trait” of the disorder, but not
the disease.
Sickle-Cell Disease
 This is an incompletely dominant disorder.
 In persons with sickle-cell disease, the red blood cells
aren’t round disks like normal red blood cells; they are
irregular.
 In fact, many are sickle shaped, like a banana with points
on both ends.
 The red blood cells do not carry oxygen well, and they get
stuck in arteries also. Therefore, people with this disease
suffer from poor circulation, anemia, poor resistance to
infection, internal bleeding, pain in the abdomen and
joints, and damage to internal organs.
 SICKLE CELL VIDEO
Sickle-Cell Disease
Incompletely Dominant Traits
 Sickle-Cell Disease
 In malaria-infested Africa, infants with sickle-cell disease
die (they got a bad chromosome from both parents), but
infants with sickle-cell trait (they got a bad chromosome
from only one parent) actually have better resistance to
malaria than a normal human being. The malaria parasite
normally reproduces inside red blood cells. But a red
blood cell of a sickle-cell trait infant kills the parasite.
 Therefore, the only people who survive well in Africa are
those with sickle cell trait. That’s why about 60% of the
population in malaria-infested regions of Africa has sickle
cell trait. Unfortunately, 25% of their offspring can get the
sickle cell disease.
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Malaria
Sex-Linked Traits
 Traits controlled by alleles on the sex
chromosomes are said to be sex-linked; an allele
that is only on the X chromosome is X-linked,
and an allele that is only on the Y chromosome is
Y-linked.
 Most sex-linked alleles are on the X
chromosome since it is larger.
X-Linked Disorders
 X-linked conditions can be dominant or
recessive, but most known are recessive.
 More males than females have the trait.
 If a male has an X-linked condition, his
daughters are often carriers, so her male
children are also likely to have the condition.
 All of the following disorders are sex-linked.
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Male Pattern baldness
 From a gene that is
inherited from the
mother.
 For you guys, if your
mother’s father was
bald, you are more likely
to be bald.
 It doesn’t matter if your
father is bald or if his
father is bald.
 You get the baldness
gene from your mother’s
father.
X-linked Recessive Disorders
 Three well-known X-linked recessive
disorders (more common in males than
females) are color blindness, muscular
dystrophy, and hemophilia.
Color Blindness
 In the human eye, there are three
different types of cone cells (remember,
they sense color vision).
 These different types are sensitive to
either the color red, green, or blue.
 The gene for the red and green cells is
on the X chromosome.
COLOR BLINDNESS TEST
 About 8% of
Caucasian men have
red-green color
blindness.
 Opticians have special
charts by which they
detect those who are
color blind.
Muscular Dystrophy
 As you can tell by the name, this disease is characterized
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by a wasting away of the muscles.
The most common form is X-linked and occurs in about
1/ 3,600 male births.
Symptoms, such as waddling gait, toe walking, frequent
falls, and difficulty in rising, may appear as soon as the
child starts to walk.
Muscle weakness progresses to the point where they
need a wheelchair.
Death usually occurs by age 20; therefore, affected
males are rarely fathers.
The disease is from a carrier mother to carrier daughter.
Muscular Dystrophy
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Hemophilia
 About 1/10,000 males is a hemophiliac.
 It is due to the absence of a clotting factor.
 It is called the bleeder’s disease because the
blood does not clot.
 Every time they get a bruise, they have to have
either a blood transfusion or an injection of a
clotting protein, which they keep in their
refrigerator since they need it so often.
X-Linked Disorders
 In the early 1900’s, hemophilia was
prevalent among the royal families of
Europe, and all of the affected males
could trace their ancestry to Queen
Victoria of England.
 Of her 26 grandchildren, five grandsons
had hemophilia and four granddaughters
were carriers.
 Because none of Queen Victoria’s
ancestors or relatives were affected, it
seems that the faulty allele she carried
arose by mutation either in Victoria or in
one of her parents.
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Hemophilia
 Her carrier daughters, Alice and Beatrice,
introduced the gene into the ruling houses of
Russia and Spain, respectively. Alexis, the last
heir to the Russian throne before the Russian
Revolution, was a hemophiliac. There are no
hemophiliacs in the present British royal family
because Victoria’s eldest son, King Edward VII,
did not receive the gene and therefore could not
pass it on to any of his descendants.
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Sex-Influenced Traits
 The length of the index
finger is sex-influenced.
 In females, an index finger
longer than the fourth finger
(ring finger) is dominant.
 In males, an index finger
longer than the fourth finger
seems to be recessive.
Stem Cell Research
Stem Cell Research
 Some human illnesses, such as diabetes
type 1, Alzheimer disease, and
Parkinson disease, are clearly due to a
loss of specialized cells. In diabetes
type 1, there is a loss of insulin secreting
cells in the pancreas, and in Alzheimer
disease and Parkinson's disease there is
a loss of brain cells. Specific types of
cells are needed to cure these
conditions.
Stem Cell Research
 Stem cells are cells that continuously divide to
produce new cells that go on to become
specialized cells. The bone marrow of adults and
the umbilical cord of incidents contain stem cells
for each type of blood cell in the body. It is
relatively easy to retrieve blood stem cells from
either of these sources. Researchers report that
they have injected blood stem cells into the heart
and liver only to find that they became cardiac
cells and liver cells respectively!
Stem Cell Research
 The skin, gastrointestinal lining, and the brain
also have stem cells, but the technology to
retrieve them has not been perfected. Also, it
has not been possible to change adult stem
cells into a fully developed specific type of cell
outside the body. If the technique is perfected,
it might be possible to change a brain stem
cell and to the type of cell needed by a
Parkinson patient.
Stem Cell Research
 Today, young, relatively infertile couples seek
assistance in achieving pregnancy and having
children. During in vitro fertilization, several eggs
and sperm are placed in laboratory glass, where
fertilization occurs in development begins. A
physician places two or three embryos in the
woman's uterus for further development, but may
hold back some encased bees fail to take hold.
Embryos that are never used remain frozen
indefinitely unless they are made available to
researchers.
Stem Cell Research
 Each cell of an embryo is called an embryonic
stem cell because it can become any kind of
specialized cell in the body.
 Researchers have already used non-human
embryonic cells to create supplies of nonhuman
specialized cells.
 Therefore, they think the same will hold true with
human embryonic stem cells.
 If so, medicine would undergo an advancement
of enormous proportions.
Stem Cell Research
 Even so, there is a down side.
 What about the embryos that had been forced to
give up the chance of becoming an adult in order
to extend the health span of those already living?
Would this be ethical?
Stem Cell Research
 In Great Britain, researchers can work with
embryos that are 14 days or younger because
embryos usually implant in the uterus around day
14. However, some people will leave that all
human beings are equal, and ought not to be
harmed or considered to be less than human on
the basis of age or size or stage of development
or condition of dependency. They believe that
embryos should not be used as a means to an
end, even good ends, such as a cure for diseases
or to save another human life.
Stem Cell Research
 President George W. Bush agreed and signed an
executive order that forbids the use of federal
funds for the purpose of creating new cell lines
derived from embryos in United States. The
order does not affect any embryonic stem cell
lines previously established nor any work with
adult stem cells. Nevertheless, some
researchers have left the United States to work in
countries where stem cell research is freely
allowed without governmental restrictions.
Stem Cell Research
 Stem cell research is a bioethical dilemma.
Some say that to think in dualistic terms is not
helpful; it isn't that an embryo is a human being or
is not a human being, it's that a fully developed
human being comes about gradually. For
instance, what would you do if there was a fire in
a fertility clinic and you were faced with the
choice of saving a five-year-old girl or a tray of 10
embryos? Which would you choose? Some
people also believe that stem cell research is
ethical, but that humans should not be cloned.
Stem Cell Research
 Should researchers have access to embryonic
stem cells or only adult stem cells? What is your
reasoning?
 Do you believe that while it is ethical to do
research with embryonic stem cells to cure human
illnesses, it is not ethical to clone humans? What
is your reasoning?
 Some researchers are mixing nonhuman and with
human embryonic stem cells in order to study
developmental differences. Is this ethical?
 You can get a complete gene map of
your unborn child -- but should you?
 http://fxn.ws/OsO6tY
Genetic Testing for Cancer
Genes
Genetic Testing for Cancer
Genes
 Several genetic tests are now available to detect
certain cancer genes. If Winn and test positive
for a particular type of defective gene, they have
an increased risk for early onset breast and
ovarian cancer. If an individual tests positive for
a different type of gene, they are at greater risk
for the development of colon cancer. Other
genetic tests exist for rare cancers as well.
Genetic Testing for Cancer
Genes
 Advocates for genetic testing say that it can alert
those who test positive for these mutated genes
to undergo more frequent mammograms or
colonoscopies. Early detection of cancer clearly
offers the best chance for successful treatment.
Others feel that genetic testing is unnecessary
because nothing can presently be done to prevent
the disease. Perhaps it is enough for those who
have a family history of cancer to schedule more
frequent checkups beginning at a younger age.
Genetic Testing for Cancer
Genes
 People opposed to genetic testing worried that a
woman with a defective gene for breast cancer
might make the unnecessary decision to have a
radical mastectomy. In a study of 177 patients
who underwent gene testing for susceptibility to
colon cancer, less than 20% received any
counseling before the test. Moreover, physicians
misinterpreted the test results in nearly one third
of the cases.
Genetic Testing for Cancer
Genes
 It's possible, too, that people who test negative
for a particular genetic VK Chin may believe that
they are not at risk for cancer. This might
encourage them not to have routine cancer
screening.
 Regular testing and avoiding known causes of
cancer such as smoking, a high fat diet, or too
much sunlight, are important for everyone.
Genetic Testing for Cancer
Genes
 Should everyone be aware that genetic testing
for certain cancers is a possibility, or should such
testing the confined to a research setting?
 If genetic testing for cancer were offered to you,
would you take advantage of it? Why or why
not?
 Our protective measures to avoid cancer more
important than testing? Explain.
Choosing Gender
Choosing Gender
 You may feel that it is ethically wrong to choose
which particular embryo can continue to develop
following in vitro fertilization.
 But what about choosing whether an X-bearing
or Y-bearing sperm should fertilize the egg?
 As you know, the sex of a child depends upon
whether an X-bearing sperm or a Y-bearing
sperm enters the eighth.
Choosing Gender
 A new technique has been developed that can
separate each type of sperm. First, the sperm
are dosed with a chemical. The X-chromosome
has slightly more DNA than the Y-chromosome,
so it takes up more die. When a laser beam
shines on the sperm, the ex-bearing sperm shine
a little more brightly. A machine sorts the sperm
into two groups on this basis. The results are not
perfect. Following artificial insemination, there is
about an 85% success rate for a girl in about a
65% rate for a boy.
Choosing Gender
 Some might believe that this is the simplest way
to make sure they have a healthy child if the
mother is a carrier of an X-linked genetic disorder
such as hemophilia or muscular dystrophy.
Previously, a pregnant woman with these
concerns had to wait for the results of an
amniocentesis test and then decide whether or
not to abort the pregnancy if it was a boy. Is it
better to increase the chances of a girl to begin
with? Or, do you believe that gender selection is
not acceptable for any reason?
Choosing Gender
 Even if it does not lead to a society with far more
members of one sex than another, there could be
a problem. Once you separate reproduction from
the sex act, it might open the door to genetically
designing children in the future. On the other
hand, is it acceptable to bring a child into the
world with a genetic disorder that may cause an
early death or a lifelong disability? Would it be
better to select sperm for girl, who at worst would
be a carrier like her mother?
Choosing Gender
 Do you think it is acceptable to choose the
gender of a baby? Even if it requires artificial
insemination at a clinic? Why or why not?
 Do you see any difference between choosing
gender or choosing embryos free of a genetic
disease for reproduction purposes?
 If selecting sperm is less expensive than
selecting embryos, should women who are
carriers of X-linked genetic disorders he
encouraged to use this method of producing
children who are free of the disease?
Designer Children
Designer Children
 Human beings have always attempted to
influence the characteristics of their children. For
example, couples have attempted to determine
the sex of their children for centuries through a
variety of methods. Amniocentesis has allowed
us to test fetuses for chromosomal abnormalities
and debilitating developmental defects before
birth. Modern genetic testing technology enables
parents to directly select children bearing desired
traits, even at the very earliest stages of
development.
Designer Children
 Recently, a couple selected an embryo to cause,
as a newborn, the individual could save the life of
his sister.
 The couple, Jack and Lisa Nash, had a daughter
with Fanconi's anemia, a rare inherited disorder
in which affected persons cannot properly repair
DNA damage that results from certain toxins.
 The disease primarily afflicts the bone marrow,
and therefore results in a reduction of all types of
blood cells.
Designer Children
 Anemia occurs, due to a deficiency of red blood
cells.
 Patients are also at high risk of infection, because
of low white blood cell numbers, and of leukemia,
because white blood cells cannot properly repair
any damage to their DNA.
Designer Children
 Fanconi's anemia may be treated by a traditional
bone marrow transplant, or by an adult stem cell
transplant, preferably from a parent or a sibling,
because the risk of rejection is lower. Adult stem
cells are almost always the preferred treatment
option, because stem cells are hardier and much
less likely to be rejected in a bone marrow
transplant. The umbilical cord of a newborn is a
rich source of adult stem cells for all types of
blood cells.
Designer Children
 The selection of an embryo on the basis of genes
is accomplished by extracting a sample of the
DNA, determining its sequence, and comparing it
with known sequences for diseases. In this case,
doctors examined the DNA of embryos to see if
they had the gene in question, that the newborn
would be healthy, and also would be able to
benefit his sister. The parents underwent in vitro
fertilization, and the 15 resulting embryos were
screened to see if they were both free of the
inherited disease in a match for their daughter.
Designer Children
 Two embryos met these requirements, but only
one implanted in the uterus and it developed into
a healthy baby boy. Adult stem cells were
harvested from the umbilical cord of the newborn
and were successfully used to treat his sister's
anemia. The physician who performed the
genetic screening stated that he has received
numerous inquiries about performing the
procedure for other couples with diseased
children
Designer Children
 This case, and other related cases, has raised a
number of ethical issues surrounding prenatal
selection of children based on genetic traits.
 While the AMA insists that selection based on
traits not related to the disease is unethical, the
AMA's share made an exception for this case,
because the child was selected for medical
reasons.
Designer Children
 Still, some people believe that it is dangerous to
bear children for the purpose of curing others,
and that it should be compared with a new form
of biological slavery.
 Others think that, soon, children will be selected
for less altruistic reasons, such as for their height,
physical prowess, or intellectual abilities.
Designer Children
 In general, do you think it is ethical to have
children to cure medically related conditions,
regardless of how fertilization occurs? If not, do
you agree with the AMA that this case is an
acceptable exception?
 Because the brother was created as a treatment
for his sister's disease, do you believe that there
is a moral obligation to provide him with
compensation?
Designer Children
 Would embryonic stem cells, to ride from Anna
boarded penis and cultured in the laboratory, be
an acceptable substitute?
 Would you willingly donate sperm or eggs for in
vitro fertilization to produce a healthy child for a
couple who could not have won because of the
risk of an inherited disease, such as Fanconi's
anemia?
Designer Children
Designer Children
Designer Children
Designer Children
Designer Children
Reproductive and
Therapeutic Cloning
Reproductive and
Therapeutic Cloning
 Reproductive cloning and therapeutic cloning are
done for different purposes. In reproductive
cloning, the desired end is an individual that is
genetically identical to the original individual. At
one time, it was thought that the cloning of adult
animals would be impossible because
investigators found it difficult to have the nucleus
of an adult cell start over, even when it was
placed in an egg without a nucleus.
Reproductive and
Therapeutic Cloning
 In March 1997, Scottish investigators announced
they had cloned a sheep called Dolly.
 How was their procedure different from all the
others that had been attempted?
 Unlike other attempts, the donor cells were
starved for the cell's nucleus was placed in in a
period starving the donor cells caused them to
stop dividing and go into a resting stage, and this
made the nuclei receptive to cytoplasmic signals
for initiation of development.
Reproductive and
Therapeutic Cloning
 By now, and it is common practice to clone all
sorts of farm animals that have desirable traits
and even to clone the rare animals that might
otherwise become extinct.
Reproductive and
Therapeutic Cloning
 In the United States, no federal funds can be
used on experiments to clone human beings.
Cloning is wasteful-- even in the case of Dolly,
out of 29 clones, only one was successful. Also,
there is concern that cloned animals may not be
healthy. Dolly was euthanized in 2003 because
she was suffering from lung cancer and crippling
arthritis. She had lived only half the normal
lifespan for her species of Sheikh.
Reproductive and
Therapeutic Cloning
 In therapeutic cloning, the desired end is not an
individual; rather, it is mature cells of various cell
types.
 The purpose of therapeutic cloning is to learn
more about how specialization of cells occurs
and to provide cells and tissues that could be
used to treat human illnesses such as diabetes,
spinal cord injuries, and Parkinson disease.
Reproductive and
Therapeutic Cloning
 There are two possible ways to carry out therapeutic
cloning. The first way is to use the exact same procedure
as reproductive cloning, except embryonic cells are
separated and each one is subjected to treatment that
causes it to develop into a particular type of cell such as
red blood cells, muscle cells, or nerve cells. Some have
ethical concerns about this type of therapeutic cloning,
which is still very experimental, because if the embryo
were allowed to continue development, it would become
an individual.
Reproductive and
Therapeutic Cloning
 The second way to carry out therapeutic
cloning is to use adult stem cells.
 Stem cells are found in many organs of the
adults body; for example, the skin has stem
cells that constantly divide and produce new
skin cells.
 The bone marrow has stem cells that produce
new blood cells as does the umbilical cord of
newborns.
Reproductive and
Therapeutic Cloning
 It has already been possible to use stem cells
from the brain to regenerate nerve tissue for the
treatment of Parkinson's disease.
 However, the goal is to develop techniques that
would allow scientists to turn any adult stem cell
into any type of specialized cell.
 Many investigators are engaged in this
endeavor. In order to do this, scientists need to
know how to control gene expression.
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