HUMAN GENETICS
Review
• Mendel – the father of genetics
• Heredity – the passing on of traits
• Homozygous Dominant – two copies of the
dominant allele ( BB)
• Homozygous Recessive – two copies of the
recessive allele (bb)
• Heterozygous – Two different alleles (Bb)
Determining Sex
• Each of us has 44 Autosomes and two SEX
CHROMOSOMES ( Total of 46
Chromosomes)
• Sex chromosomes determine your SEX
• XX ( female ) or XY ( male)
Sex Linked and X/Y linked
Traits
• Some genes are located on the X or Y chromosomes.
• If there is error that occurs on either the X or Y
chromosome then it is called SEX LINKED.
• X- Linked means that it is carried on the X Chromosome
• Y – Linked means that it is carried on the Y chromosome
What is Linkage?
• Linkage occurs when two genes occur close
together on a chromosome
• The are always passed on together.
• The Location or LOCI can be found
indicated on a Chromosome map.
What are polygenetic traits?
Polygenic traits are controlled by two or more genes
(a single inherited phenotypic trait that is
controlled by two or more different genes- think
back to tossing the pennies 6 times in our baby lab to
determine what skin color your baby would have)
Examples include:
• Skin color
• Eye color
• Height
• Foot size
Watch the video: https://www.youtube.com/watch?v=7Q29SE8zYyg
What are multiple allele traits?
• This happens when there are 3 or more
alleles of the same gene for a single trait.
• Ex Blood Types A, B, O Groups. They are all
variations of the gene for blood type indicated
by an I
• Types A and B are CODOMINANT .
• Type O is RECESSIVE TO A and B.
Mutations Review
Mutations- In Genes
1.
Point Mutation- when there is change in one
nitrogenous
base.
-Substitutions – when one base is changed but
everything else is unaffected.
-Insertions
-Deletions
2. Frameshift – when one or more base (s)s
( nucleotide) are substituted, added or deleted that
changes how the codons are read.
Example of Gene a Mutation
Sickle cell anemia – one A is substituted
by a T and causes the RBC to become
sickle shaped.
Affects people of African descent.
Provides some protection from malaria.
Chromosomal Mutations
1. Deletions – when part of a chromosome is
deleted.
2. Insertions- when part of a chromosome is
inserted.
3. Inversion – when a piece of a chromosome is
flipped.
4. Translocation – when a piece of a chromosome
breaks off and attaches somewhere else.
5. Nondisjunction – when homologous pairs fail to
separate during meiosis.
Examples of Chromosomal
Mutations
1. Down’s Syndrome – 3 copies of
chromosome 21 ( TRISOMY)
2. Kleinfelters syndrome – XXY (TRISOMY)
3. Turner’s syndrome- XO ( MONOSOMY)
Why do mutations occur?
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Chemical mutagens
Viruses
Radiation
High Temperature
Remember that some cancers can be caused
by mutations that lead to uncontrolled cell
division.
Other Genetic Disorders
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Huntington’s
Dwarfism
Polydactyl
Cataracts
Albinism
PKU (
Phenylketonuria)
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Tay Sachs
Cystic Fibrosis
Muscular Dystrophy
Hemophilia
Color Blindness
(Blue = Sex-linked )
Cystic fibrosis
• Autosomal recessive
disorder that affects
1/2000 Caucasians.
• Cystic fibrosis is an inherited
disorder that causes severe
damage to the lungs,
digestive system and other
organs in the body.
• A defective gene causes the
secretions to become sticky
and thick. Instead of acting
as a lubricant, the secretions
plug up tubes, ducts and
passageways, especially in
the lungs and pancreas.
Tay-Sachs
• Autosomal recessive
disorder
• This defective gene
causes the body to not
make a protein called
hexosaminidase A.
• Without this protein,
chemicals called
gangliosides build up
in nerve cells in the
brain, destroying
brain cells.
Phenylketonuria (PKU)
• Autosomal
recessive
disorder
• A disorder that increases the levels of a substance called
phenylalanine in the blood. Phenylalanine is a building block of
proteins (an amino acid) that is obtained through the diet. It is
found in all proteins and in some artificial sweeteners.
• A buildup can result in the following symptoms: musty odor,
skin rashes, neurological issues (seizures), delayed
development, and behavioral and social issues.
Albinism
• Autosomal recessive
disorder
• Individuals have little
or no pigment in
eyes, skin, or hair.
• Cells don’t produce
the normal amount
of melanin.
Sickle- Cell Anemia
• Autosomal recessive disorder that
affects 1/500 African-Americans and
1/12 African- Americans are carriers.
• Individuals with this disorder have atypical hemoglobin
molecules called hemoglobin S, which can distort red blood
cells into a sickle, or crescent, shape.
• Signs and symptoms of sickle cell disease usually begin in
early childhood. Characteristic features of this disorder
include shortness of breath, pain due to blood clots,
swelling of hands and feet, frequent infections, delayed
growth, and vision problems.
Huntington’s Disorder
• Autosomal dominant
disorder that affects
1/10,000 people.
• An inherited disorder
in which nerve cells in
the brain break down
over time.
• Eventually results in
uncontrolled
movements,
emotional problems,
and loss of cognitive
abilities.
Blood Types
• Autosomal
inheritance that
involves multiple
alleles.
• Remember A and B
are co-dominant.
• Blood type is determined by
the antigens on the surface
of the red blood cell.
• Can have type A, B, AB, and
O.
Hair Color, Eye Color, Skin
Color, & Height
• Polygenic inheritance
Color-Blindness
• Recessive, sex-linked
inheritance.
• Condition
characterized by
the inability to
clearly
distinguish
different colors
of the
spectrum.
• Recessive, sex-linked
inheritance.
Hemophilia
• A rare disorder in which
your blood doesn't clot
normally because it lacks
sufficient blood-clotting
proteins (clotting factors).
• If you have hemophilia,
you may bleed for a longer
time after an injury than
you would if your blood
clotted normally
Muscular Dystrophy
• Recessive, sex-linked
disorder.
• Disorder characterized
by progressive
weakness and
degeneration of the
skeletal or voluntary
muscles which
control movement.
Down’s Syndrome
• Inherited through
non-disjunction in
sex chromosomes.
• Disorder in which the
individual has distinct
facial features, upward
slanted eyes, poor
muscle tone, short
fingers and toes, small
hands and feet, short
height, and intellectual
disabilities.
Turner’s Syndrome
• Inherited through
non-disjunction in
sex chromosomes.
• Disorder that affects
females only.
• These females have a
short stature, delayed
puberty, infertility, heart
defects, and learning
disabilities.
Klinefelter’s Syndrome
• Inherited through
non-disjunction in
sex chromosomes.
• Males with this disorder
have an extra X
chromosome.
• These males experience
reduced muscle mass,
reduced facial and body
hair, enlarged breast
tissue, taller than average
stature, weak bones, and
smaller genitals.
Pattern Baldness
• Inherited through a
sex-influenced trait
• Individuals with
baldness have a
receding hairline and
hair thinning on the
crown of their head.
How can we detect genetic
Disorders?
Genetic Screening
Examine the family history of the individual.
- Pedigree ( a chart showing inheritance of
traits or disorders over generations )
Karotyping ( a picture of your choromosomes)
What if a problem is suspected?
Genetic counseling – advise couples trying to have babies of
the risks that may affect their offspring.
Genetic Testing:
• Amniocentesis – fluid is drawn form amniotic sac to detect
disorders
• Fetoscopy –surgery or samples taken from fetus
• Chorion Villi sampling- used for karoytyping
• Ultrasonography
Cancer and Vitamin D
• Vitamin D produced by the body
as a response to sun exposure;
it can also be consumed in food or supplements.
• Vitamin D helps your support your immune system,
helps prevent and fight cancer, and in angiogenesis or
the formation of new blood vessels.
• To obtain vitamin D you need to be out in the sun
however if you are out in the sun to much there is the
risk of altering DNA in the skin and causing skin
cancer. Need a balance.
• Your pancreas makes a hormone called insulin.
It's what lets your cells turn glucose from the
food you eat into energy. People with type 2
diabetes make insulin, but their cells don't use it
as well as they should. Doctors call this insulin
resistance.
• Genetics, obesity, and diet can all be a factor in
causing this type of diabetes.
Type 2 Symptoms
• Symptoms include increased thirst, frequent
urination, hunger, fatigue, and blurred
vision. In some cases, there may be no
symptoms.
• Diabetes can cause serious health problems, such as heart
disease, stroke, and eye and foot problems.
•
Prediabetics also can cause health problems. The good news is
that type 2 diabetes can be delayed or even prevented.
• The longer you have diabetes, the more likely you are to
develop health problems, so delaying diabetes by even a few
years will benefit your health.
• You can help prevent or delay type 2 diabetes by losing a
modest amount of weight by following a reduced-calorie
eating plan and being physically active most days of the
week.
Type II Diabetes
Prevention
• Lose weight and keep it off. You may be able to prevent or delay diabetes by
losing 5 to 7 percent of your starting weight.1 For instance, if you weigh 200
pounds, your goal would be to lose about 10 to 14 pounds.
• Move more. Get at least 30 minutes of physical activity 5 days a week. If you
have not been active, talk with your health care professional about which activities
are best. Start slowly to build up to your goal.
• Eat healthy foods most of the time. Eat smaller portions to reduce the amount of
calories you eat each day and help you lose weight. Choosing foods with less fat
is another way to reduce calories. Drink water instead of sweetened beverages.
Environmental Influences
• An environmental influence is any external
factor such as air, water, minerals, and other
organisms surrounding and affecting a
given organism at any time.
Background ( Review)
• A gene is expressed when a protein is made.
• Proteins are composed of amino acids
• A zygote is formed when an egg is fertilized by a sperm.
• A zygote divides and differentiates into many different
types of cells such as blood, nerve, and muscle cells via cell
differentiation.
– Cell differentiation is when some genes are selectively
turned on or off in a cell.
What Influences Gene
Expression?
• Gender:
– Pattern Baldness- expressed mostly in males
due to higher levels of testosterone.
– Lactation
– Breast Cancer
Other Environmental Influences
• Pollutants
• Day Light Exposure Time
• Color of Light
• Temperature