Transcript Genetic Disorders - SandersBiologyStuff

Genetic Disorders
Inherited in different ways

Gene mutations
Autosomal / Sex-linked
Dominant / recessive/ codominant

Chromosomal mutations
Too many- trisomy
Too few- monosomy
Deletions of large portions of the chromosome
 Autosomal Recessive
 Lack of enzyme
hexosaminidase A (hex A),
which breaks down fatty acids in
brain in nervous tissue
 Symptoms begin to appear at 46 months
 Developmental delay, loss of
motor skills and mental
functions, blindness, deafness,
paralysis, non-responsive to the
environment
 Death by 5 years
 Found primarily in those
descendants of Ashkenazi Jews

1/30 American Jews carry the
gene
 Autosomal recessive Chromosome #7 - Point
mutation stops production of a
protein in the lungs and
pancreas

Prevents cells from
transporting Cl- ions out of
the cell
 Lung Congestion



Abnormally thick mucus lining
in lungs
Chronic Bacterial Infections
(pneumonia)
Treated with antibiotics, lung
transplant, and new genetic
engineering treatments
 Northern European descent
Albinism
Autosomal recessive
On one of many genes
controlling pigment
production
Lack of pigment in the
skin, hair, and eyes
 Autosomal recessive- Chromosome #12
 Do not contain enzyme phenylalanine
hydroxlyase (PAH) that breaks down amino
acid phenylalanine into amino acid tyrosine



Phenylalanine builds up in brain
Toxic to central nervous system (CNS)
Learning Difficulties, seizures
 Tested at birth
 PKU – 1/10,000

U.S.  1/50 carry PKU allele
 Regulated by Strict diet


Low protein: no meat, eggs, dairy
No Aspartame: sugar substitute sold as Equal
or NutraSweet
 Contains amino acid phenylalanine – 50%
Achondroplasia
Autosomal dominant
1 of 6 kinds of Dwarfism
(each has different
characteristics
 Normal torso length with
shortened limbs
 Most common form of
dwarfism
 Homozygous dominant
zygotes will miscarry
 Autosomal Dominantchromosome #4
 Lethal due to
degeneration of brain
cells
 Symptoms onset around
ages 35-50
 Lose control over
muscles causing
uncontrolled
movements, loss of
intellectual faculties,
and emotional
disturbance
Hypercholesterolemia
Familial high cholesterol
Autosomal codominant
on Chromosome #19
Cells have reduced ability
to remove cholesterol
(lipids) from the blood
which causes a build up
in the arteries (called
atherosclerois)
Blockage leads to early
age heart attacks
Hypercholesterolemia
Treated with medicines like Lipator,
Mevacor, Zocor
 Autosomal Codominant
 Defective Hemoglobin on
RBCs caused by 1
nucleotide base deletion
 shape change
 Damage to brain, heart,
lungs
 Carriers are protected from
malaria
 African descent; 1/10
African Americans in US is
a carrier
 Presence of gene on a
sex chromosome (X or
y)
 X chromosome is larger
than y  more genes
carried on the X
 X-Linked Genes: genes
found on X chromosome



Appear mostly in males
Only one copy of X;
nothing to counteract
“bad gene”
Females would need
two copies to express
trait
 Holandric Traits: genes on the y chromosome;
carry genes for male sexual characteristics
 Absence of these genes causes female
development
 Small arm of y chromosome responsible for
individuals that have a sex chromosome
combination that does not match their
appearance
XX males and XY females due to absence
or presence of SRY factor
 Ghengis Khan
Mongolian warrior 13th century
8% of men living in region that was once
Mongolian empire have same y
chromosome
 sex-linked recessive
 On 1 of 2 genes
producing clotting factor
located on the X
chromosome
 Most Common in males
 “Bleeder’s Disease”
 Bleeding spontaneously
and in joints
 Queen Victoria:
descendents affected
with hemophilia
 sex-linked recessive
 Most Common in males

1/3500
 Progressive muscle
weakening and
enlargement
 Dystrophin

Protein that provides
support for the cell;
without it, cell enlarges
and explodes
 sex-linked recessive
 On 1 of 3 color vision
genes on the X
chromosome
 Cannot distinguish
between different
colors
 Most common type is
red/green
colorblindness
 Heterozygous female
is considered a carrier
 Chromosomal
(Autosomal)
 Trisomy 21
 Mild to severe learning
disabilities, Distinct Facial
Features, Heart Defects,
low muscle tone
 Most Common Birth
Defect – 1/700 births
 Mother’s Age 30 –
1 in 1000
 Mother’s Age over 45 –
1 in 25
 Can live until 50s
 Chromosomal (Sex
chromosomes)
 Trisomy XXY male
 1 per 1,000 males (most
do not know they have an
extra X chromosome)
 Feminine Characteristics,
Sparse facial and body
hair, dental problems, tall
 Infertile (cannot produce
sperm)
 Chromosomal (Sex
Chromosome)
 Monosomy XO female
 Infertile, Short stature,
 Overweight, Some
learning difficulties,
Webbed Neck, no
menstruation
 1 out of 2,000 live births.
 96-98% do not survive to
birth
 Chromsomal
(Autosomal)
 Trisomy 18
 Elfin Appearance, Low
set ears, Clenched
hands, Heart disease,
Kidney problems, Low
birth weight, Small
head, Small jaw
(micrognathia)
 1 out of 3,000 live births
 90% die within first 6
months
 Chromsomal
(Autosomal)
 Trisomy 13
 Cleft Lip and Palate,
Polydactyly, Cleft lip or
palate, Close-set eyes
(eyes may actually fuse
together into one), Lowset ears, Severe learning
difficulties, Seizures.
Small eyes, Small head
 1 in 10,000 births
 80% die within first month
 “Cat’s Cry” Syndrome
 Deletion of a portion
of Chromosome 5
 Developmental delay,
Moon-shaped face,
Heart disease,
Malformed larynx
 1 in 216,000 births
 Normal lifespan
Aniridia-Wilms Tumor Syndrome
#11 Deletion of upper arm
Developmental delay,
Blindness, Tumors on
kidneys
1 in 50,000,000 births
Short lifespan
Thirteen Q Deletion Syndrome
#13 Deletion of lower arm
Developmental Delay,
Malformed face, No
thumbs, Heart disease
1 in 500,000 births
Short lifespan
Triple X Syndrome
Tall stature, Mild facial
characteristics (increased width
between eyes and
proportionately smaller head
size), learning disabilities,
speech and language delays,
poor coordination, introverted,
normal sexual development
1 in 2,500 births
Normal lifespan
XYY Syndrome
XYY only; #23 Trisomy
Highly variable: sometimes
taller than average, increased
risk of learning disabilities,
delayed speech and language
skills, behavioral problems,
normal sexual development
1 in 1,000 males
 Genomic Imprinting: variation in
phenotype expression depending
on which parent gave the
chromosome



Chromosome “remembers” which
parent it came from
EX: Deletion of Chromosome 15
Prader-Willi: uncontrollable eating,
diabetes, mental retardation
Deletion of portion of paternal 15

Angleman’s: behavior problems, some
mental retardation
 Deletion of portion of maternal 15