Transcript Genetic Disorders

Genetic Disorders
Genetic Disorders
Can be from changes in base sequence
of DNA
Can also be chromosomal
abnormalities:
Missing a whole chromosome
An extra chromosome
Missing fragment of chromosome
Mutations
Change in the “normal” base sequence
in DNA
Leads to change in the sequence of
amino acids in a protein
Most genetic disorders are caused by
this
Cystic fibrosis
Most common genetic disorder in caucasians of
western european descent
A recessive mutation on chromosome #7, missing
three bases of DNA
1 in 3200 births= rr
10 million carriers in the U.S. (Rr)
Defective protein in cell membrane causes a thick
mucus to clog lungs, pancreas, digestive tract,
reproductive tract
Chronic (reoccuring) lung infections, digestion
problems
Phenylketonuria
A mutation that is a recessive allele on
chromosome # 12
1 in 50 people is a carrier
1 in 10,000 babies born with it
A defective enzyme that is supposed to convert
the amino acid phenylalanine in to tyrosine
If they eat foods with phenylalanine, it
accumulates in brain cells, causes them to die
Causes mental retardation
Can’t eat foods high in protein, because proteins
are made of amino acids, including phenylalanine
Sickle cell anemia
Mutation in gene on chromosome #11
1 in 12 people of African ancestry are carriers
Hemoglobin protein is defective
Red blood cells begin their life shaped normally,
slowly lose round shape and become stiff and
curved
Symptoms include:
Circulation problems
Infections
Internal bleeding
Jaundice
Pain
fatigue
Sickle cell, cont.
Treatments:
Transfusion
Vitamins
Pain medication
Average life span:
42-48 years
Chromosomal Abnormalities
Egg= 23 Sperm= 23
Zygote= first cell, SUPPOSED to have 46
chromosomes, 1 of each
Chromosome pairs 1-22 are called
autosomes
During the formation of GAMETES
(sperm and egg) if the chromosomes
don’t separate from each other then the
gametes could end up with the wrong
number of chromosomes
If the egg has a wrong # of
chromosomes and it gets fertilized, the
zygote and every single cell after it
begins to divide will have the wrong # of
chromosomes
Most of the time, if the zygote
has the wrong number of
chromosomes then it will not
divide, and it will die before
the woman even knows she
was pregnant.
There are a FEW
EXCEPTIONS:
Down’s Syndrome (Trisomy 21)
During the formation of an egg or sperm,
chromosome pair #21 didn’t separate= a
gamete had an extra #21 chromosome
Person’s genotype is 47(21)
Symptoms of Down’s
Syndrome
HUGE variation among individuals
Mild to severe mental retardation
Almond shaped eyes
Shorter limbs, stature
Poor muscle tone
Large space between first and second toe
Large, protruding tongue
Heart defects
Gastroesophageal reflux disease
Thyroid problems
Prenatal Testing
Women are offered a test called the
AFP test (alpha feto protein test) at 1618 weeks of gestation
Elevated level of certain proteins in
mother’s blood stream can be an
indicator of a baby with down’s
syndrome
Turner’s Syndrome
Person is X0 for genotype of sex chromosomes (45, X0)
Lacking a y chromosome makes the person a female
Symptoms
Short stature
Swelling of hands/feet
Broad chest
Low hairline
Low-set ears
Sterile
*rudimentary ovaries
*obesity
*short metacarpal IV
*webbed neck
*poor breast development
*heart problems
Kleinfelter’s Syndrome
Person’s genotype is XXY (47,XXY)
Male (because of presence of y
chromosome)
1 in 500 males
Symptoms include:
Hypogonadism- produces little
or no hormones
Breast enlargement
Little facial hair, body hair
Narrow shoulders
Harlequin Type Ichthyosis
Characterized by a thickening of the
•
keratin layer in fetal human skin.
• In addition , the eyes, ears , mouth
and other appendages may be
abnormally contracted.
Primordial
Dwarfism
Dwarfism:
Achondroplasia