Download DNA Mutations and Disorders 2010

DNA Mutations & Disorders
Normal Protein Formation
1. A segment of DNA
strand is copied by
mRNA in the nucleus.
2. mRNA leaves nucleus
and goes to ribosome in
cytoplasm.
3. Ribosome “reads”
mRNA and calls for
specific amino acids.
4. Amino acids linked
together to form protein
chain.
Abnormal Protein Formation
• Mutations in DNA will code for wrong
amino acids which will cause wrong protein
to form.
• Can lead to cell death, disease, disorders
What is a mutation?
• Any change in a gene or
chromosome.
• Most are natural and have no
effect on the organism- can
promote good genetic diversity
• Some are harmful
• Some are lethal (cause death in
offspring)
• Some are good for the organism
(ex: some mosquitoes have a
gene mutation that makes them
resistant to pesticide- leads to
evolution of stronger mosquito
populations)
What are some types of mutations?
1. Point mutationchange in ONE
single nitrogen base
in ONE gene.
•
•
This change causes
the code to change
so amino acids are
not put in correct
order.
EX: albinism, sickle
cell anemia
Types of Point Mutations
A. Silent- one letter change
but no change in amino
acid= no change in
protein structure= no
problems
B. Missense- one letter
change causes changed
amino acid= wrong
protein structure
C. Nonsense- one letter
change causes STOP
codon in middle of amino
acid chain= protein won’t
get made
(Normal)
What are some types of mutations?
2. Chromosome Mutations
(Frameshift)- changes in
MANY genes, entire
segments of chromosome
are messed up.
• Because more genes are
involved, usually more
harmful to the organism.
A. Deletion- part of
chromosome is lost
B. Duplication- part of
chromosome is repeated
twice
C. Inversion- chromosome
breaks, piece is turned
over & reinserted upside
down
D. Translocation- two
chromosomes affectedone piece detaches &
reattaches to another
chromosome
A
B
C
D
E. Insertion- a nitrogen base is
added which causes nitrogen
bases to shift to the right,
throws off amino acid
sequence.
F. Nondisjunction- a
chromosome pair fails to
separate properly during
meiosis (some sperm/egg get
too many chromosomes, some
get too few).
– Monosomy- too few (45
chromosomes)
– Trisomy- too many (47
chromosomes)
What are some causes of
mutations?
1. Mutagen- anything that causes a mutation in DNA in a cell.
–
–
–
–
–
UV light
Radiation
X rays
chemicals in tobacco smoke, synthetic materials, pollution
viruses
What is the difference between
germ cell mutation & somatic cell
mutation?
• Germ Cell mutation:
– Occurs in gametes
(sperm/egg)
– Does not affect
individual person
– CAN be passed to
offspring
• Somatic Cell mutation
– Occurs in body cells
– Affects individual in
which it occurs
– CANNOT be passed
to offspring
– If occurs in genes that
control cell
reproduction can
become CANCER.
What are some methods of
detection?
• Ultrasound- sound
waves generate image of
unborn child. Detect
abnormalities of limbs,
organs, etc.
What are some methods of
detection?
• Amniocentesis: use
needle to extract
fluid/cells surrounding the
fetus. Chromosomes can
then be karyotyped
What are some methods of
detection?
• Karyotyping: pictures of
chromosomes are matched
up according to size
Difference between Autosomes
& Sex Chromosomes
1. Autosomes- first 22
pairs of chromosomes in
karyotype
2. Sex Chromosomes- last
pair of chromosomes
that determine gender
3. Male karyotype- sex
chromosomes are a big
chromosome (X) and a
small chromosome (y)
4. Female karyotype- sex
chromosomes are two
big chromosomes (XX)
What are some types of genetic
disorders
1. Autosomal Dominantif dominant gene is
present, person will
have disorder
– Huntington’s disease
– Achondroplasia
HUNTINGTON’S DISEASE
• Caused by dominant allele
• Develops after age 30
• Lose muscle control, mental deterioration,
& eventually death.
• No cure
Achondroplasia
• Dwarfism
• Defect in gene that
controls cartilage
formation
• Shortened stature
• Some have normal
sized torso but
shortened limbs.
What are some types of genetic
disorders?
2. Autosomal
Recessive- must have
two recessive genes
to show disorder
–
–
–
–
Phenylketonuria
Cystic Fibrosis
Tay-Sachs
Sickle cell anemia
PHENYLKETONURIA
• Also called PKU
• Must inherit two recessive alleles to show this
disease.
• Unable to synthesize the enzyme that breaks
down the amino acid phenylalanine.
Phenylalanine accumulates and kills brain cells.
• Tested at birth- if present, put on diet low in
phenylalanine (no milk) for first six years to
prevent brain damage.
CYSTIC FIBROSIS
• Also called CF
• Caused by a recessive allele
on chromosome #7.
• Serious digestive problems, thick mucus
that clogs lungs. Makes breathing &
digesting food very difficult.
TAY-SACHS DISEASE
• Caused by two recessive
alleles
• Occurs mostly in Jewish
families
• Fats accumulate in brain
cells, mental deficiency,
delayed development,
blindness
• Usually results in death
within first few years of
life.
SICKLE-CELL ANEMIA
• Red blood cells are
half moon shaped
instead of round.
• Clog blood vessels,
depriving tissues of
oxygen- causes
severe pain,
weakness.
• Found more often in
people of African
descent.
What are some types of genetic
disorders?
3. Sex-Linkeddisorder on sex
chromosomes
– Klinefelters
syndrome
– Turner’s syndrome
– XYY males
KLINEFELTERS SYNDROME
•
•
•
•
Males with an extra X chromosome
XXY
Sterile
Some degree of mental deficiency
TURNER’S SYNDROME
•
•
•
•
Females with only one X chromosome.
XO
Sterile
Short, with thick, webbed necks, mild
mental deficiency.
XYY MALES
• Males with extra Y
chromosome
• taller than average
• Produce more
testosterone, some
say more aggressive