Transcript ppt
Mutations &
Genetic Disorders
Headings
Vocabulary
Important Information
Mutations
Mutation:
Any mistake or change in the DNA sequence
Point mutation:
Change in
one nitrogen
base in DNA
Ex: albinism
Chromosomal Mutation:
Changes in
chromosome
structure
1) INVERSION:
the order of genes on
a chromosome is
inverted
2) TRANSLOCATION:
•the movement of a
chromosome fragment to
a nonhomologus
chromosome
3. DELETION
Loss of a few bases
Loss of large regions
of a chromosome
4. DUPLICATION
Duplication of a few
bases
Duplication of large
regions of a
chromosome
Crossing Over
Occurs
when
chromosomes
exchange genes.
2 chromosomes
overlap.
Some genes
cross over and
switch places
NONDISJUNCTION
Nondisjunction:
chromosome pair fails
to separate properly
during meiosis
Monosomy:
gamete has 1 less
chromosome than it
should
45 chromosomes
is the result
Ex: Turner syndrome
Missing a sex
chromosome
Trisomy:
Gamete has 1
more chromosome
than it should
Result is 47
chromosomes
Ex: Down’s
Syndrome
Extra
#21
chromosome
Methods of Detection
Chorion villi sampling:
•Take sample of the chorion
–(membrane surrounding
fetus)
•Chemical tests and Karyotyping performed
Ultrasound:
Sound waves are used to
generate an image of the
unborn child.
Used to detect abnormalities of
limbs, organs, etc.
Amniocentesis:
• Fluid surrounding the fetus is drawn out by
needle
• Fetal cells are collected and grown in a lab.
• Chromosomes can be then Karyotyped
Autosomal Disorders
Down’s
Syndrome (Trisomy 21)
Patau’s
Syndrome (Trisomy 13)
Edward’s
Syndrome (Trisomy 18)
Down’s Syndrome (DS)
Excess
# 21 chromosome
Prenatal testing can be done
Result of chromosomal mutation
1 in 900 people born with this
Likelihood of having a child with DS
increases with advancing maternal age
Symptoms: mental retardation, upward
slant to eyes, small mouth, abnormal ear
shape, decreased muscle tone
No cure
Patau’s Syndrome &
Edward’s Syndrome
Cardiac
abnormalities
Very severe conditions
Most affected infants
die during first few
weeks of life
Deletion Disorders
Angelman
Syndrome
Prader-Willi
Syndrome
Angelman Syndrome
Inappropriate
laughter with
convulsions
Poor
coordination
Mental
retardation
Prader-Willi Syndrome
Extremely
floppy
Obesity (constantly
hungry)
Mild mental
retardation
Sex Chromosome Disorders
Klinefelter’s
Turner’s
Fragile
Syndrome
Syndrome
X Syndrome
Klinefelter’s Syndrome
47, XXY
1 in 1000 male live births
Mild learning difficulties
Taller than average with
long lower limbs
Show mild enlargement of
breasts
Infertile (absence of
sperm)
Treat with testosterone
Turner’s Syndrome
45,
X
Low incidence
Look normal
Ovarian failure
Normal intelligence
Short stature
Estrogen therapy
Fragile X Syndrome
Most
common inherited
cause of mental
retardation
1 in 2000 males
High forehead,
prominent jaw, autism
Gap in X chromosome
Single Gene Disorders
Cystic
Fibrosis
Hemophilia
Sickle
Cell Anemia
Phenylketonuria
Cystic Fibrosis (CF)
Recessive disorder
Mutation stops production of
protein in lung cells,
pancreas
Thick mucus, bacterial
infections in lung
“sweat test”
Most common in
Caucasians (1 in 3300)
Chest percussions, diet
supplements
Shortened life expectancy
Hemophilia
Sex-linked
Failure
of blood to clot
Rare in females
Injections with clotting factors to stop
bleeding episodes
$350,000 a year in treatment
Sickle Cell Anemia
Mutation in blood protein
“sickle” shape to RBC
Screening tests
Most common in African-Americans
(1 in 375)
Pain associated with blocked vessels, causes
anemia (fatigue)
Common where
mosquito-borne
malaria is present
PKU
Mutation disrupts function of enzyme
Leads to high phenylalanine levels in brain
(poisons)
Mental retardation, epilepsy
Screening newborns (heel prick)
1 in 10,000 Caucasian births
Extremely rare in African-Americans
Look normal
Need low-protein diet,
smelly formulas
Self Quiz:
Quick Check for Understanding
1. Which of the following is an X-linked
disorder?
b. heel prick
c. X-ray
A. testosterone injections
b. chest percussions
4. Turner’s Syndrome is
A. amniocentesis
3. How are CF patients treated?
c. Down syndrome
2. How is PKU tested for?
A. Angelman B. hemophilia
A. 45, X
b. 46, XX
c. 47, XXY
5. Patients with Klinefelter’s Syndrome are
A. all male
b. all female c. male or female