Karyotypes
and
Pedigrees
Inheritance of Genetic Traits
Karyotypes
 Biologists photograph cells in mitosis,
when the chromosomes are fully
condensed and easy to see (usually in
metaphase).
 The chromosomes are then arranged
in homologous pairs.
Karyotypes
 The homologous pairs are then placed
in order of descending size. The sex
chromosomes are placed at the end.
 A picture of chromosomes arranged
in this way is known as a karyotype.
Labeling a Karyotype
 To label a karyotype correctly, first list the
number of chromosomes found in the
karyotype. Ex. 46
 Secondly, list the type of sex chromosomes
found in the karyotype. Ex. XX
 Lastly, list the any abnormalities at the
appropriate chromosome number.
Normal Human Female: 46, XX
Normal Human Male: 46, XY
What are abnormalities?
 Sometimes, during meiosis, things go
wrong.
 The most common error is
nondisjunction, which means “not
coming apart”.
 If nondisjunction occurs , abnormal
numbers of chromosomes may find
their way into gametes, and a
disorder of chromosome numbers may
result.
Autosomal Chromosome
Disorders
 Two copies of an autosomal chromosome
fail to separate during meiosis, an individual
may be born with THREE copies of a
chromosome.
 This is known as a “Trisomy”
 Trisomy 13, Trisomy 18, Trisomy 21.
Down Syndrome
 Most common, Trisomy 21 (down syndrome)
 1 in 800 babies born in U.S. with Trisomy 21.
 Mild to severe mental retardation
 Increased susceptibility to many diseases and a
higher frequency of other birth defects.
Down’s Syndrome
or Trisomy 21
Kleinfelter’s syndrome
XXY
 Males with some
development of breast
tissue normally seen in
females.
 Little body hair is
present, and such
person are typically
tall, have small testes.
 Infertility results from
absent sperm.
Turner’s Syndrome
One X
Female inherits only one X
chromosome
 Turner syndrome is
associated with
underdeveloped ovaries,
short stature, webbed, and
is only in women.
 Bull neck, and broad chest.
Individuals are sterile, and
lack expected secondary
sexual characteristics.
Turner’s Syndrome
Pedigrees
 A type of “family tree”







Circle – female
Square – male
Shaded – has the trait
Unshaded – does not have the trait
½ shaded – is a carrier of the trait
Horizontal line – represents marriage
Vertical line – connects parents to children
Marriage
Male-DAD
Female-MOM
Carrier
Has the trait
Male-Son
Male- Son
Female-daughter Female-daughter
Oldest to youngest
Pedigrees
Example of Sex linked. Notice only females
are carriers and only males have the trait:
Pedigree Charts - Autosomes
Autosomal Dominant – Trait
appears in every generation
Autosomal Recessive – Trait
appears when two parents
by chance carry the hidden
allele.
More
Genetic
Disorders
Sickle Cell Anemia
 An inherited, chronic
disease in which the red
blood cells, normally
disc-shaped, become
crescent shaped. As a
result, they function
abnormally and cause
small blood clots within
your veins
 Most commonly found in
African Americans (can be
linked to the incidence of
malaria).
Cystic Fibrosis
 Body produces abnormally thick mucus in
the lungs and intestines
 The thick mucus fills the lungs making it
hard to breathe
 Common among Caucasians…1 in 20 are
carriers
 Most die from disease in
Early 30’s
Tay-Sachs disease
 Monogenic, autosomal recessive
 Central nervous system degrades, ultimately
causing death.
 Most common among people of Jewish,
eastern Europe descent.
Other Genetic Disorders
 Musclular Dystrophy



Sex-linked, defective gene for muscle protein.
Progressive weakening and loss of skeletal
muscle. Body get weaker and weaker and
slowly stops working.
In U.S., 1 out of every 3000 males born has
condition.
Hemophilia
 A person’s blood clots
very slowly or not at all
 Do not produce one of the proteins needed for
normal blood clotting
 Small bumps and bruises may cause internal
bleeding that can’t be controlled
 One can bleed to death with only a small cut or
bruise
 Sex-linked disorder – occurs more frequently in
males
X-linked Inheritance pedigree chart
Huntington’s Disease
 Huntington's disease
(HD) is an inherited,
degenerative brain
disorder which results
in an eventual loss of
both mental and
physical control.
Patients have "dancelike movements" which
refers to the
uncontrolled motions
often associated with
the disease.
Phenylketonuria or PKU
People with PKU cannot consume any product that
contains aspartame.
PKU is a metabolic disorder that results when the
PKU gene is inherited from both parents
 A low protein diet must be followed.
 Brain damage can result if the diet is not followed
causing mental retardation…and mousy body
odor (phenylacetic acid is in sweat).
ALS
 The disease strikes people between the ages
of 40 and 70, and as many as 30,000
Americans have the disease at any given
time
 This mutation is believed to make a
defective protein that is toxic to motor nerve
cells.
 A common first symptom is a painless
weakness in a hand, foot, arm or leg, other
early symptoms include speech swallowing
or walking difficulty
Color Blindness
 Cause: x-linked
recessive
 1/10 males have,
1/100 females have.
Why the difference?
 Individuals are unable
to distinguish shades
of red-green.
 Are you color blind?
Albinism
 Patients are unable to produce skin or eye
pigments, and thus are light-sensitive
 Autosomal recessive
The very tragic disease…
hairy ears
Y-linked trait, which are
rare
 symptoms…hairy ears
 Only 1 cure known….