Genetic Disorders & Testing
Polydactyl- dominant trait
Warning: sensitive material
What is a mutation?
Results of a mutation?
review
2 types of mutationsGene or Chromosomal
ReviewTypes 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
Chromosomal Mutation• Change in # or structure of
the chromosome • Mitosis & meiosis• usually not passed on
because zygote dies
Ex. Deletion
Inversion
Duplication
translocation
review
Nondisjunctionoccurs when a chromosome pair fails to separate properly
during meiosis-can happen to any chromosome pair2 types:
• 1. Monosomy: when gamete has one less chromosome than it should
• only 45 chromosomes (need 46)
• Ex: Turner syndrome-occurs only in females
2. Trisomy: when gamete has one more chromosome than it should
•47 chromosomes( need 46)
•Ex: Down’s syndrome, extra #21
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 DisordersDisorder: 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 DisordersDisorder: AlbinismFacts: 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 DisordersDisorder: 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 DisordersDisorder: 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), & French-Canadians 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, jaundice
Incidence: 1 in 375 African Americans
Treatments: bone marrow transplants, medicines
Autosomal Dominant DisordersDisorder: Huntington’s DiseaseFacts: 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
here in Ga.
Autosomal Dominant Disorders
Disorder: Achondroplasia
Facts: stunted bone growth; type of DwarfismPoint 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: hormone
Therapy given estrogen
And growth hormone.
Chromosomal mutation DisordersDisorder: 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*write Xm Xm , XmY
*most disorders are x-linked, recessiveDisorder: 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 deathIncidence: mainly in males ; Royal Family
Treatments: inject themselves with purified clotting factors to prevent or stop bleeding
Sex-linked DisordersDisorder: 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
1. Karyotyping: pictures of chromosomes are matched up according to size4 Methods of
detection
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
Top Related