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Genetics ~ Part III
Karyotypes and Pedigrees
Karyotype- a chart of
chromosomes pairs
Male
Karyotype
Any individual with at least one
Y chromosome is male and
without one Y is female.
XX- Female
XY –Male
Down Syndrome (trisomy-21)
Autosomal nondisjunction
affected individuals survive to
adulthood
 It occurs in about 1 and 700 live
births
- There is a third chromosome on the
21st pair.
- They have varying degrees of mental
disability.
- The incidence is higher among older
mothers, especially those over 40.
Characteristics: short, slanted eyes,
thick tongue
SEX CHROMOSOME
NONDISJUNCTION –
Unusual numbers of sex
chromosomes
Turner’s Syndrome
XO
One X chromosome is missing
• FEMALES ONLY!
• Monosomy X – gets only
ONE X chromosome
•Sterile female
•Low intelligence
•No breasts (no secondary sex
characteristics)
Klinefelter syndrome
XXY
-Extra X chromosome
-MALES ONLY!
- causes a male to be
sterile
-No beard, no deep voice, no
masculine muscle tone (no
secondary sex characteristics)
Most of these individuals lead
normal lives, but they can not have
children and some may have some
degree of mental retardation.
Superman Syndrome
XYY
 Male
 Has an extra Y chromosome
 On average 3” taller than your average male
 Clinical phenotype of this syndrome is
normal
RECESSIVE AUTOSOMAL
DISORDERS-Deals with
chromosome pairs #1-22
Cystic Fibrosis
Excess mucus in lungs
Mostly found in Caucasian
population
Chromosome #7
Phenylketonuria (PKU)
Lack of normal skin
pigmentation
Mental retardation
Can prevent with special diet
Chromosome #12
Absence of certain enzyme
Damage to Central Nervous
System
Tay-Sachs Disease
 Lipids (fats) in brain cells
 Affects Central Nervous System
 Mental deficiency
 Fatal, usually causes death by
age 2
 Mostly in Jewish population
 Chromosome #15
DOMINANT AUTOSOMAL
DISORDERS - Deals with
chromosome pairs #1-22
Huntington’s Disease
Chromosome #4
Memory loss
Uncontrolled movements
Onset occurs between the ages of
30-50 (middle age)
Forgets things, stumbles
Cause: abnormal repeating of
certain bases
CODOMINANT AUTOSOMAL
DISORDERS
Sickle Cell Anemia
 Sickle-shaped red blood cells
 Difficulty breathing
 Nitrogen base is changed, affects
HEMOGLOBIN that carries oxygen
 Mostly in African Americans
 Cells clot
 Capillaries are cut causing
bleeding internally.
 Chromosome #11
 Pedigree-
a graphic
representation of genetic
inheritance from generation to
generation
Pedigree Symbols
Normal female
Affected female
Carrier/heterozygous female
Normal male
Affected male
Carrier/heterozygous male
Death
Married
Parent and Offspring
A
carrier is represented by a
half shaded circle or square.
They are heterozygous- they
have a recessive gene but it
does not show.
DNA
FINGERPRINTING
aka
GEL ELECTROPHORESIS
Why ?? To determine whether
suspects have been at a crime
scene/location
Who?? Law enforcement
 How
does it work???
Small DNA samples can be obtained
from blood, hair, skin, and copied
millions of times.
The DNA is cut into fragments of
different lengths
DNA fragments can then be separated
by electrophoresis, and compared with
those obtained from a crime scene
 The
genes follow standard
patterns from person to person
 BUT the non-coding segments
produce distinct combinations
of patterns that are unique to
each individual
 SO unique fingerprints can be
used to identify a single person.
No
two people have the
same DNA (except identical
twins)