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. DeletionInversionDuplicationtranslocation

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 DisordersDisorder: PKU

Facts: missing an enzyme that breaks down Phenyalanine (in milk) /it accumulates in the central nervous system

Caused by a point mutationSymptoms: 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 mutationSymptoms: pain in joints, anemia, weakness, jaundice

Incidence: 1 in 375 African AmericansTreatments: 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 DisordersDisorder: 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 separateSymptoms: mental retardation, slanted eyesIncidence: 1 in 900; most cases not inheritedTreatments: none

Aneuploidy(caused by Nondisjunction/ Trisomy)

Disorder: Klinefelter Syndrome Facts: XXY - Trisomy- chromosomes failed to

separateSymptoms: male, taller than average,

longer limbs, sterile, may have some mental retardation

Incidence:Treatments: none

Aneuploidy(caused byNondisjunction/ Monosomy)

Disorder: Turner’s SyndromeFacts: female, only 1 X b/c of NondisjunctionSymptoms: sterile, lack of sexual development(no

ovaries), short statureIncidence:Treatments: hormone Therapy given estrogenAnd growth hormone.

Chromosomal mutation DisordersDisorder: Cri Du Chat SyndromeFacts: missing piece of chromosome # 5 (deletion)Symptoms: mental retardation, high-pitched cry

that sounds like a cat.Incidence: avg. 1 in 40, 000Treatments: 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 MDSymptoms: muscle loss & weakness

Incidence: mainly in males; all ethnic groups have an equal chance of MD

Treatments: physical therapy , braces, wheelchair

Sex-linked DisordersDisorder: 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-blindnessFacts: recessive, x-linked disorder; Cones in eyes(color

receptors) are absent or lack of pigmentSymptoms: 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