Transcript Mutations & Genetic Disorders

Warning: sensitive material
Chp 14 Genetics
Genetic Disorders & Testing
Polydactyldominant trait
review
What is a mutation?
Results of a mutation?


2 types of mutations
Gene or Chromosomal
Review
Types of Gene mutations
• 1. Point mutation: change
in one nitrogen base in
DNA;
• Ex. Substitution
2. Frameshift Mutation
–Ex. insertion or deletion of a base
–shifts entire sequence for translation
review
Chromosomal Mutation
• Change in # or structure of
the chromosome
• Mitosis & meiosis
• usually not passed on
because zygote dies
Ex. Deletion
Inversion
Duplication
translocation
Nondisjunction
occurs when a chromosome pair fails to separate properly
2 types: during meiosis-can happen to any chromosome pair
• 1. Monosomy: when
2. Trisomy: when gamete
gamete has one less
has one more chromosome
chromosome than it
than it should
should
• only 45 chromosomes
•47 chromosomes( need 46)
(need 46)
•Ex: Down’s syndrome,
• Ex: Turner syndromeextra #21
occurs only in females
Don’t forget: you
have 23 pairs(46
chromosomes) in
each cell in your
body
GENETIC DISORDERS
• THESE ARE THE ONES YOU NEED TO
KNOW FOR THE TEST!
• Autosome- lst 22 pairs of chromosomes
• Sex-linked- 23rd pair
Autosomal Recessive Disorders
Disorder: Progeria
Facts: rapid aging disease,
Caused by point mutation
Symptoms: thin, bald, old-looking skin
Incidence: rare (live to teens or maybe 30’s)
Treatments: none
Autosomal Recessive Disorders
Disorder: Albinism
Facts: can be caused by a autosomal recessive,
autosomal dominant or sex-linked trait; point
mutation
• Symptoms: absence of pigment in hair, skin, eyes;
• defect of melanin production
• Photophobic- sunlight painful to eyes
Incidence: common in European descent; less common
in African Americans & Asians
Treatments: none
Autosomal Recessive Disorders
Disorder: PKU
Facts: missing an enzyme that breaks down Phenyalanine
(in milk) /it accumulates in the central nervous system
Caused by a point mutation
Symptoms: can cause mental retardation, abnormal growth
patterns
Incidence: rare in African Americans & Japanese;
more common in Irish
Treatments: test newborns- change diet
Autosomal Recessive Disorders
Disorder: CF- Cystic Fibrosis
Facts: mucus in lungs & digestive tract is very
thick ; caused by point mutation
Symptoms: makes breathing & digestion
difficult
Incidence: most common in Caucasians(whites) 1 in
2000 white; 1 in 25 carry recessive allele.
Treatments: frequent lungs infections, daily
therapy is needed to loosen & remove mucus
Autosomal Recessive Disorders
Disorder: Tay-Sachs
Facts: disorder of central nervous system: brain &
spinal cord
• missing an enzyme which breaks down lipids;
accumulates in brain
Symptoms: everything goes in reverse; deteriorates
Incidence: 1 in 27 Jews, Cajuns(Lousiana), & FrenchCanadians are carriers
Treatments: none; happens within 1st year most children
don’t live past 5
Autosomal Recessive Disorder/
Codominance
Disorder: Sickle-Cell Anemia
Facts: sickle-shaped blood cells block/clot up blood
vessels; point mutation
Symptoms: pain in joints, anemia, weakness
Incidence: 1 in 375 African Americans
Treatments: bone marrow transplants, medicines
Autosomal Dominant Disorders
Disorder: Huntington’s Disease
Facts: degeneration of nerve cells in the brain because of
faulty gene on chromosome # 4(point mutation)
Symptoms: mood swings, depression, memory loss,
decline in movements & speech
Death usually occurs 10-20 years after onset of symptoms. Symptoms
begin between ages of 30-50.
Incidence:Every child of a parent with the disorder
has a 50% chance of inheriting Huntington's
Disease.
Treatments: none
*Mother murdered/assisted suicide/ her sons in the nursing home
Autosomal Dominant Disorders
Disorder: Achondroplasia
Facts: stunted bone growth; type of Dwarfism
Point mutations
Symptoms: Torso is normal but arms and legs are
short.
Incidence: 1 out of 25000
– Only heterozygotes have this disorder.
– Homozygous dominant condition
results in death of the embryo.
Treatments: none
Aneuploidy
(caused by Nondisjunction)
Disorder: Down’s Syndrome (Trisomy 21)
Facts: most common reason for mental retardation;
chromosomes failed to separate
Symptoms: mental retardation, slanted eyes
Incidence: 1 in 900; most cases not inherited
Treatments: none
Aneuploidy
(caused by Nondisjunction/ Trisomy)
Disorder: Klinefelter Syndrome
Facts: XXY - Trisomy- chromosomes failed to
separate
Symptoms: male, taller than average, longer
limbs, sterile, may have some mental
retardation
Incidence:
Treatments: none
Aneuploidy
(caused byNondisjunction/ Monosomy)
Disorder: Turner’s Syndrome
Facts: female, only 1 X b/c of Nondisjunction
Symptoms: sterile, lack of sexual development(no
ovaries), short stature
Incidence:
Treatments: none
Chromosomal mutation Disorders
Disorder: Cri Du Chat Syndrome
Facts: missing piece of chromosome # 5 (deletion)
Symptoms: mental retardation, high-pitched cry
that sounds like a cat.
Incidence: avg. 1 in 40, 000
Treatments: none
Sex-linked Disorders
m Xm , XmY
*write X
*most disorders are x-linked, recessive
Disorder: Muscular Dystrophy (MD) (duchenne’s
only)
Facts: recessive, x-linked; many types of MD
Symptoms: muscle loss & weakness
Incidence: mainly in males; all ethnic groups have
an equal chance of MD
Treatments: physical therapy , braces, wheelchair
Sex-linked Disorders
Disorder: Hemophilia
Facts: recessive, x-linked; blood does not have
clotting factors
Symptoms: bleed excessively or to death
Incidence: mainly in males ; Royal Family
Treatments: inject themselves with purified
clotting factors to prevent or stop bleeding
Sex-linked Disorders
Disorder: Color-blindness
Facts: recessive, x-linked disorder; Cones in eyes(color
receptors) are absent or lack of pigment
Symptoms: cannot tell difference between certain colors
Incidence: mainly in males- passed from mother;
•
red-green color blindness most common
• Seeing only black/white is rare
Treatments: none
4 Methods of
detection
1. Karyotyping: pictures of
chromosomes are matched up
according to size
methods of detection cont
• 2. Ultrasound: sound waves/ image. Used to detect
abnormalities of limbs, organs, etc.
• 3. Amniocentesis: fluid surrounding the fetus is drawn out
by needle, fetal cells collected/ grown Chromosomes
karyotyped
4. Chorion villi sampling: a sample of the
chorion (membrane surrounding fetus) is taken,
chemical tests and karyotyping are performed