Human Genetics
Genetic
Experiment 626
Karyotyping:
technique for examining the
chromosome make up of an
organism
shows chromosomes arranged
by size:
– homogulous pairs
a way of detecting abnormalities
Karyotyping:
chromosomes paired
–Total of 46 chromosomes
–Or 23 pair:
22 autosomes, somatic cells, body
cells &
1 pair of sex chromosomes
XX = female
XY = male
Sex- Linkage:
Genes located on the sex
chromosomes:
–genes found on the
x chromosome = x linked
–genes found on the
y chromosome = y linked
a gene found on either the x or y
chromosomes = sex linked
STOP!!! CK POINT!!
Topic: Intro to Human Genetics
Identify the following:
What is/are:
1. Karyotypes
2. Sex- linked traits
Mutations:
any change in the genetic
hereditary material of the cell
2 forms:
–inheritable mutations – occur in the
sex cells
–non inheritable mutations – occur in
the somatic cells (autosomes, body
cells)
2 Types of inheritable mutations:
ADD TO YOUR NOTES!!
1. Chromosomal Mutations
And
2. Gene mutations
STOP!!! CK POINT!!
Topic: Mutations 1
What is a mutation?
What are the 2 types of
inheritable mutations?
Chromosomal Mutations:
change in the structure of a
chromosome
the loss of an entire
chromosome or addition of a
chromosome
– Examples Include:
a. Nondisjunction
Chromosome Mutation Cont.
A. Nondisjunction:
failure of chromosomes to
separate during meiosis
–ex. Down syndrome – extra
chromosome # 21
–Ex .trisomy 18, trisomy 13
Nondisjunction:
Nondisjunction
Down syndrome (trisomy 21):
Nondisjunction:
Patau syndrome (trisomy 13):
serious eye, brain, circulatory defects as
well as cleft palate. 1:5000 live births.
Children rarely live more than a few
months.
Nondisjunction
Edward's syndrome (trisomy 18):
almost every organ system affected Children
rarely live more than a few months.
Other Examples of Nondisjunction:
Sex chromosome :
Sex chromosome aneuploids
1. XO = Turners Syndrome
2. XXY = Klinefelter Syndrome
3. XXX = Triplo-X Syndrome
4. XYY =Jacob Syndrome
Turners Syndrome:
XO individuals are genetically female, however,
they do not mature sexually during puberty and
are sterile. Short stature and normal
intelligence. (98% die before birth)
XXY = Klinefelter Syndrome
Male sex organs; unusually small testes, sterile.
Breast enlargement and other feminine body
characteristics. Normal intelligence.
XXX = Triplo-X Syndrome
XXX females. 1:1000 live births - healthy
and fertile - cannot be distinguished from
normal female except by karyotype
STOP!!! CK POINT!!
Topic: Nondisjunction
What is Nondisjunction?
When does it occur? ( Be Specific)
Identify 3 genetic mutations
resulting from nondisjunction.
– What is the cause for each?
Chromosome mutations (structure):
translocation –
a section of
one chromosome is
transferred to a
nonhomogulous
chromosome
addition – a portion of
a chromosome is added
Chromosome mutations (structure):
deletion – a portion of a chromosome is
deleted
Cri-du-Chat Syndrome (segmental
deletion)
inversion – order of genes on a
chromosome is changed
Chromosomal mutationDeletion:
Example - Cri du
chat (cry of the cat):
A deletion of a small
portion of
chromosome 5;
these children have
severe mental
retardation, a small
head with unusual
facial features, and
a cry that sounds like a
distressed cat.
In summary
Chromosomal Mutations:
Chromosomal
abnormalities can cause
serious mental or physical
disabilities,
Structure of the
chromosome has been
compromised
The number of
chromosomes is incorrect
STOP!!! CK POINT!!
Topic: Mutations 2
1. Identify 4 structural chromosomal
mutations.
2. How are each of the 4
chromosomes mutated?
3. What is Turners Syndrome?
Gene Mutations
Point Mutation – the substitution, addition,
or removal of a single nucleotide
– substitutions, 1 nucleotide in a codon
is replaced with a different nucleotide,
resulting in a new codon.
sickle cell anemia (also called sickle
cell disease) is a point mutation
substituting Adenine for Thymine in a
single DNA codon,
Gene Mutations Cont.
Frame Shift Mutation -the addition
or deletion of a single nucleotide
causes the remaining codons to
be incorrectly grouped
–Addition/removal – a single
nucleotide is added or removed
– Addition and Deletion Mutations
sickle cell
Welcome to Discovery Education Player
Characteristics of Mutations:
1. most are harmful to the
organism
2. they are random
3. most are recessive traits
4. Can be beneficial to the
organism when the mutation
helps the organism to adapt to
the environment.
Mutagenic Agents:
radiation - x-rays, radioactive
isotopes, cosmic rays, ultraviolet
rays
chemicals – saccharin, nitrates,
carcinogens
Human Genetic Traits & Disorders
X- linked Traits:
traits controlled by the female sex
chromosome
symbolized by a character on 1 of
the chromosomes
–XX’ X’ carries the trait
–The female = the carrier
–The trait is not visible in the female
Examples of Sex linked traits:
X- linked
Ex. Hemophilia –blood disorder
in which blood does not clot
properly
Ex. Color blindness – cannot
distinguish between red and
green
X-linked traits cont.
Symbols for constructing a Punnett
square (sex-linked trait)
– XX normal female
Know
– XY normal male
These!!!!
– X’X carrier female
– X’Y male with hemophilia
http://www.macmed.ttuhsc.edu/Morgan/ble
edingdisorders/pages/newpage26.htm
Ex. Hemophilia
Hemophiliac male x carrier female
Genotype
Phenotype
Hemophilia cont.
Normal male x female carrier
Genotype
Phenotype
Multiple Alleles:
2 or more alleles for a
particular trait
alleles are expressed as
codominant
ex. Blood types
Human Blood Types:
Phenotype
A
B
AB
O
Genotype
IAIA, IAi
IBIB, IBi
AB
ii
Blood Types & Punnett Squares;
What are the
possible outcomes
for a heterozygous
A blood type
crossing
with a homozygous
B blood type?
Genotypes
Phenotypes
Blood Type Cont.
Construct a punnett square showing a
cross b/w a blood type O person with a
heterozygous B blood type person
Genotype
Phenotype
Why?
THINK!
Raise your hand to answer…
WHY Blood typing
important?
RBC
agglutination
Put your skills to the test!
Look at the handout provided:
“Using Blood tests
to Identify Babies”
Polygenic Traits:
traits controlled by 2 or more alleles
expressed as incomplete
dominance
ex. Eye color, height, and skin color
This pattern of inheritance is
identified has a wide range of
phenotypes (skin & hair color).
THINK…
How is multiple alleles
different from polygenic
traits? (look in your
notes!)
Go SU!!
Genetic Disorders:
– Genetic screening or studying Karyotypes
can show possible genetic disorders
Amniocentesis – Karyotyping and
analyzing amniotic fluid for fetal cells
Chorionic villi sampling – piece of the
placenta that is studied for genetic
abnormalities
–Ex. PKU: a genetic disorder that does not
allow the baby to breakdown phenylalanine ,
can cause severe brain damage
–Can be detected and eliminated with special
STOP!!! CK POINT!!
Topic: Genetic Disorders
1. What is the difference among:
Multiple Alleles
Sex-Linked Traits
Polygenic Traits
2. What is amniocentesis?
Disorders associated with
Genetics:
Cystic Fibrosis
Tay - Sacs Disease
Phenylketonuria (PKU)
Huntington’s disease
Albinism
Cystic Fibrosis
Symptoms
–Mucous clogs the lungs and
pancreas
–Usually do not survive into
adulthood
–White population most effected
Tay-Sachs
Symptoms:
–Deterioration of the nervous
system
–Usually do not survive adulthood
–European descents most
effected
PKU
Failure of the brain to
develop during infancy
If untreated, death in early
childhood
Controlled by diet!!
Huntington’s Disease
Carried on an autosome (Dom)
Symptoms:
–Forgetfulness
–Appears in 30’s-40’s
–Loss of muscle control
–Uncontrollable muscle spasms
–Mental illness
–death
In your pkt:
Get into your groups:
> 1 min.
Get owl text books
Same place as yesterday
Turn to pg 91-92
– Begin answering questions
– Popsicle sticks!!