Download Cat-Eye Syndrome

Genetic
Mutations
Mutations …
• are changes in the
genetic material
• can be good or bad
• can be on a single
gene or the whole
chromosome
What is a karyotype?
• Picture of your
chromosomes
• Arranged from largest
to smallest
• quickly identify
chromosomal changes
4 Types of Genetic Disorders
• Single gene
–
–
–
–
–
Change in the DNA sequence
More than 6000 known disorders
Autosomal or sex linked
1 in 200 births
cystic fibrosis, sickle cell anemia, Marfan
syndrome, Huntington’s disease
Types of Genetic Disorders
• Multifactoral
– combination of environmental factors and
mutations in multiple genes
– more complicated
– heart disease, high blood pressure, Alzheimer’s
disease, arthritis, diabetes, cancer, and obesity
Types of Genetic Disorders
• Chromosomal
– abnormalities in chromosome structure as
missing or extra copies or gross breaks and
rejoining
– Down Syndrome
Types of Genetic Disorders
• Mitochondrial
– rare type of genetic disorder
– caused by mutations in the non-chromosomal
DNA of mitochondria
Genetic Disorders
• On our chromosomes are a total of about 100,000 genes.
Among these 100,000 genes, each person has on average
5-8 bad genes. However, these seldom have any effect at
all. But sometimes there are serious errors in our genetic
code and these can give us the blueprint for genetic
disorder. When we have a serious genetic error, there are
three primary ways that the error can be inherited (passed
from generation to generation). These three patterns of
inheritance are:
• Dominant genetic disorders
• Recessive genetic disorders
• Sex-linked genetic disorders
Dominant Genetic Disorders:
• In the dominant genetic disorder pattern of
inheritance, one bad gene from either parent
will cause the genetic disorder. Since only
one bad gene causes the disorder, if either
parent has the disorder the chance of the
child inheriting the bad gene and
developing the disorder is 50% with each
conception.
Recessive Genetic Disorders:
• To develop a recessive genetic disorder
both parents must contribute the same
defective gene. The parents usually don't
have the disorder, but are carriers for the
disorder. They carry one defective gene,
which is recessive, and one normal
dominant gene.
Sex-linked Genetic Disorders:
• These disorders occur due to errors in the 23rd pair of
chromosomes (the chromosomes responsible for gender).
These genetic disorders occur only in males. Since males
have an XY sex chromosome combination, they are
vulnerable to defects on their X chromosome that lacks a
partner gene on the Y. These disorders do not appear in
females (which are XX) because if one of the X
chromosomes has an affected gene, the partner X
chromosome carries a normal gene. In females, the other X
will compensate any defect on one X. Since males get a Y,
there is no compensation. Although the female can carry a
defective gene, females do not develop the disorder – they
are carriers for the disorder.
Sex-linked Traits
• Traits (genes) located on the sex
chromosomes
• Sex chromosomes are X and Y
• XX genotype for females
• XY genotype for males
• Many sex-linked traits carried on
X chromosome
copyright cmassengale
14
Sex-linked Traits
Example: Eye color in fruit flies
Sex Chromosomes
fruit fly
eye color
XX chromosome - female
Xy chromosome - male
copyright cmassengale
15
Sex-linked Trait Problem
• Example: Eye color in fruit flies
•
(red-eyed male) x (white-eyed female)
XR Y
x
XrXr
• Remember: the Y chromosome in males does
not carry traits.
Xr
Xr
• RR = red eyed
• Rr = red eyed
R
X
• rr = white eyed
• XY = male
Y
• XX = female
copyright cmassengale
16
Sex-linked Trait Solution:
Xr
XR
XR
Xr
Y
Xr Y
Xr
XR
Xr
Xr Y
50% red eyed
female
50% white eyed
male
copyright cmassengale
17
Other Genetic Disorders:
• Other genetic disorders do not fall neatly
into one of these three patterns. These
involve having too many or too few
chromosomes.
Turners Syndrome
1 in 5,000 births
45 chromosomes
X only
#23 Monosomy
Nondisjunction
Turners Syndrome
96-98% do not survive to birth
No menstruation
No breast development
No hips
Broad shoulders and neck
Cri-Du-Chat Syndrome
1 in 216,000 births
46 chromosomes
XY or XX
#5 Deletion of lower
arm
Cri-Du-Chat Syndrome
Moon-shaped face
Heart disease
Mentally retarded
Malformed larynx
Normal lifespan
Aniridia-Wilms Tumor
Syndrome
1 in 50,000,000 births
46 chromosomes
XY or XX
#11 Deletion of upper arm
Aniridia-Wilms Tumor Syndrome
Mentally retarded
Growth retarded
Blindness
Tumors on kidneys
Short lifespan
Thirteen Q Deletion
Syndrome
1 in 500,000 births
46 chromosomes
XY or XX
#13 Deletion of lower arm
Thirteen Q Deletion Syndrome
Mentally retarded
Deformed face
No thumbs
Heart disease
Short lifespan
Prader-Willi Syndrome
1 in 5,000,000 births
46 chromosomes
XY=97%
XX=3%
#15 Deletion of lower arm
Prader-Willi Syndrome
Small bird-like head
Mentally retarded
Respiratory problems
Obesity
Short lifespan
Eighteen Q Deletion
Syndrome
1 in 10,000,000 births
46 chromosomes
XY or XX
#18 Deletion of lower arm
Eighteen Q Deletion Syndrome
Mentally retarded
Heart disease
Abnormal hands and feet
Large eyes
Large ears
Normal lifespan
Cat-Eye Syndrome
1 in 1,000,000 births
46 chromosomes
XY or XX
#22 Deletion of bottom
arm
Cat-Eye Syndrome
Fused fingers and toes
Mentally retarded
Small jaw
Heart problems
Normal lifespan
Four-Ring Syndrome
1 in 10,000,000 births
46 chromosomes
XY or XX
#4 Inversion
Four-Ring Syndrome
Cleft palate
Club feet
Testes don’t descend
Short lifespan
Down Syndrome
1 in 31,000 births
46 chromosomes
XY=97%
XX=3%
#14/21 Translocation
Down Syndrome
Trisomy
1 in 1,250 births
47 chromosomes
XY or XX
#21 Trisomy
Nondisjunction
Down Syndrome
Short, broad hands
Stubby fingers
Rough skin
Impotency in males
Mentally retarded
Small round face
Protruding tongue
Short lifespan
Patau’s Trisomy Syndrome
1 in 14,000 births
47 chromosomes
XY or XX
#13 Trisomy
Nondisjunction
Patau’s Trisomy Syndrome
Small head
Small or missing eyes
Heart defects
Extra fingers
Abnormal genitalia
Mentally retarded
Cleft palate
Most die a few weeks after birth
Edward’s Trisomy
Syndrome
1 in 4,400 births
47 chromosomes
XX=80%
XY=20%
#18 Trisomy
Nondisjunction
Edward’s Trisomy Syndrome
Small head
Mentally retarded
Internal organ abnormalities
90% die before 5 months of age
Jacob’s Syndrome
1 in 1,800 births
47 chromosomes
XYY only
#23 Trisomy
Nondisjunction
Jacob’s Syndrome
Normal physically
Normal mentally
Increase in testosterone
More aggressive
Normal lifespan
?
Klinefelter Syndrome
1 in 1,100 births
47 chromosomes
XXY only
#23 Trisomy
Nondisjunction
Klinefelter Syndrome
Scarce beard
Longer fingers and arms
Sterile
Delicate skin
Low mental ability
Normal lifespan
Triple X Syndrome
1 in 2,500 births
47 chromosomes
XXX only
#23 Trisomy
Nondisjunction
Triple X Syndrome
Normally physically
Normal mentally
Learning disabilities
Taller than average
Behavior Problems
Huntington’s
Chromosome 4 mutation
*involuntary twitching or movement
*onset 40 yrs.
*deterioration of the CNS that affects
muscle control
Sickle-cell Anemia
Moon shaped RBC that has low hemoglobin
• Shows up more often in African Americans; or
whose ancestors once inhabited parts where
malaria is a high risk.
• Sickle-shaped cells clog capillaries so that cells
cannot get oxygen and nutrition
• Blood transfusions, pain killers, and drugs
• Pain, strokes, jaundice.
Cystic Fibrosis
Chromosome 7 mutation
• Affects mucus, salivary and sweat glands.
• Many respiratory problems
• Thick, sticky mucus in lungs and digestive
tracts.
Tay-Sachs
• No Hex A enzyme
• Recessive genetic disorder most often found in
Jewish or eastern Europe origin.
• Appears in children starting at 6 mo.
• Child cannot metabolize a certain lipid which
incases the CNS and prevents the brain from
expanding.
• Fat builds up in the brain causing blindness &
paralysis
• Death occurs in early childhood
Hemophilia
• Blood has less than 1% of the normal
clotting factor
• Bleeds longer because blood won’t clot.
Color-blindness
• Cones in the eye do not perceive certain
colors
• Most common form is reds/greens but
some are brown/blue
• Seen as gray