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Human Genetic Human Genetic Disorders Disorders Biology Biology

Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

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Page 1: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Human Genetic Human Genetic DisordersDisorders

BiologyBiology

Page 2: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Genetic TestingGenetic Testing

Amniocentesis and Chronic Villi Amniocentesis and Chronic Villi SamplingSamplingSample of amniotic fluid or placentaSample of amniotic fluid or placenta

KaryotypingKaryotypingTaking a picture of the chromosomes in Taking a picture of the chromosomes in

a cella cell

Page 3: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

What Can Go Wrong?What Can Go Wrong?

Nondisjunction (most deadly)Nondisjunction (most deadly)Improper separation of homologous Improper separation of homologous

chromosomes in meiosis I or chromatids in chromosomes in meiosis I or chromatids in mieosis II or mitosis (at an early embryonic mieosis II or mitosis (at an early embryonic stage)stage)

Results in too many or too few Results in too many or too few chromosomes in daughter cellschromosomes in daughter cells

DNA mutationsDNA mutationsMore specific letter-changes in codeMore specific letter-changes in codeResults in the inability to make certain Results in the inability to make certain

proteinsproteins

Page 4: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Nondisjunction Causes:Nondisjunction Causes:

Aneuploidy: cells that have too many Aneuploidy: cells that have too many or too few chromosomes are or too few chromosomes are aneuploid.aneuploid.Monosomy: only 1 of a pair presentMonosomy: only 1 of a pair presentTrisomy: 3 instead of 2 presentTrisomy: 3 instead of 2 present

Page 5: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Incidence of Genetic Incidence of Genetic AbnormalitiesAbnormalities

Maternal AgeMaternal AgeAt 25 years, 17% of eggs may have At 25 years, 17% of eggs may have

chromosomal abnormalities. At 40 years, chromosomal abnormalities. At 40 years, up to 74% may contain abnormalities.up to 74% may contain abnormalities.

Spontaneous Abortion Spontaneous Abortion (Miscarriage)(Miscarriage)Two-thirds of all pregnancies are lost. Two-thirds of all pregnancies are lost.

These miscarriages are called These miscarriages are called spontaneous abortionsspontaneous abortions..

Genetic mutation causes an estimated 60% Genetic mutation causes an estimated 60% of these spontaneous abortions.of these spontaneous abortions.

Page 6: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Family PedigreesFamily Pedigrees

Page 7: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Down SyndromeDown Syndrome

Caused by Trisomy 21Caused by Trisomy 21Symptoms:Symptoms:

Mental retardationMental retardationFlattened faceFlattened faceSparse, straight hairSparse, straight hairShort statureShort statureHigh risk of cardiac anomalies, leukemia, High risk of cardiac anomalies, leukemia,

cataracts, and digestive blockagescataracts, and digestive blockagesAverage life expectancy: 55 years (much Average life expectancy: 55 years (much

longer than it used to be even just longer than it used to be even just recently)recently)

Page 8: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Edward SyndromeEdward Syndrome

Caused by Trisomy 18Caused by Trisomy 18Symptoms:Symptoms:

Mental and physical retardationMental and physical retardationSkull and facial abnormalitiesSkull and facial abnormalitiesDefects in all organ systemsDefects in all organ systemsPoor muscle tonePoor muscle toneAverage life expectancy: 2-4 monthsAverage life expectancy: 2-4 months

Page 9: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Patau SyndromePatau Syndrome

Caused by Trisomy 13Caused by Trisomy 13Symptoms:Symptoms:

Mental and physical retardationMental and physical retardationSkull and facial abnormalitiesSkull and facial abnormalitiesDefects in all organ systemsDefects in all organ systemsCleft lip & large triangular noseCleft lip & large triangular noseExtra digitsExtra digitsAverage life expectancy: 6 months (but Average life expectancy: 6 months (but

½ die in the first month)½ die in the first month)

Page 10: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Sex Chromosome Sex Chromosome AbnormalitiesAbnormalities

Turners Syndrome (X0 - female)Turners Syndrome (X0 - female)1 in 20001 in 2000Infertile, sexually underdeveloped, short Infertile, sexually underdeveloped, short

stature, narrow aorta, normal intelligencestature, narrow aorta, normal intelligenceKlinefelter Syndrome (XXY - male)Klinefelter Syndrome (XXY - male)

1 in 10001 in 1000Reduced sexual maturity, secondary Reduced sexual maturity, secondary

sexual characteristics (breast swelling), sexual characteristics (breast swelling), no sperm productionno sperm production

Page 11: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Triple X Syndrome (XXX – female)Triple X Syndrome (XXX – female)1 in 15001 in 1500Slight IQ reduction, menstrual irregularitiesSlight IQ reduction, menstrual irregularities

Jacob Syndrome (XYY – male)Jacob Syndrome (XYY – male)Incidence unknown (lack of diagnosis)Incidence unknown (lack of diagnosis)Tall, acne issues, speech/reading problemsTall, acne issues, speech/reading problemsDisproportionate number incarceratedDisproportionate number incarcerated96% are normal (most don’t realize they 96% are normal (most don’t realize they

have this condition)have this condition)

Sex Chromosome Sex Chromosome AbnormalitiesAbnormalities

Page 12: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

DNA MutationsDNA MutationsCri du Chat Syndrome (cry of the cat)Cri du Chat Syndrome (cry of the cat)

Deletion on part of chromosome 5Deletion on part of chromosome 5Fragile XFragile X

Repeated sequences of CCG on X Repeated sequences of CCG on X chromosomechromosome

Normal = 6-50 copiesNormal = 6-50 copiesCarrier (males) = 50-230 copiesCarrier (males) = 50-230 copiesDisorder = more than 230 copiesDisorder = more than 230 copiesCauses mental retardation (2Causes mental retardation (2ndnd behind behind

only Down Syndrome)only Down Syndrome)

Page 13: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Autosomal Recessive Autosomal Recessive DisordersDisorders

Cystic Fibrosis (CF)Cystic Fibrosis (CF)Mutation on chromosome 7Mutation on chromosome 7Thick mucous develops in lungs and Thick mucous develops in lungs and

digestive tractdigestive tractDifficulty breathing & lung infectionsDifficulty breathing & lung infectionsMost common lethal genetic disorderMost common lethal genetic disorder1 in 25 is a carrier1 in 25 is a carrier1 in 2500 has disorder1 in 2500 has disorder

Page 14: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

More Autosomal RecessiveMore Autosomal Recessive

Tay Sachs DiseaseTay Sachs DiseaseFatty substance builds up in neuronsFatty substance builds up in neuronsGradual paralysis and loss of nervous Gradual paralysis and loss of nervous

function by age 4-5function by age 4-5Single defective enzymeSingle defective enzymeHeterozygote carriers (Hh) do not have Heterozygote carriers (Hh) do not have

disorder, but are resistant to Tuberculosisdisorder, but are resistant to TuberculosisEspecially common in Jewish population Especially common in Jewish population

(central and eastern European descent), (central and eastern European descent), up to 11% are carriersup to 11% are carriers

Page 15: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

More Autosomal RecessiveMore Autosomal Recessive

PKU (Phenylketonuria)PKU (Phenylketonuria)Can’t break down amino acid Can’t break down amino acid

phenylalanine (missing critical enzyme)phenylalanine (missing critical enzyme)Phenylalanine builds up and interferes Phenylalanine builds up and interferes

with nervous system leading to mental with nervous system leading to mental retardation and even deathretardation and even death

Early screening Early screening phenylalanine phenylalanine restricted diet for children with disorderrestricted diet for children with disorder

Page 16: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Sickle-Cell AnemiaSickle-Cell AnemiaAbnormality in hemoglobin (carries Abnormality in hemoglobin (carries

oxygen in our red blood cells)oxygen in our red blood cells)Cells become sickle-shaped and clog Cells become sickle-shaped and clog

blood vessels (painful)blood vessels (painful)Causes poor circulation, jaundice, Causes poor circulation, jaundice,

anemia, and hemorrhaginganemia, and hemorrhagingHeterozygote carriers (Hh) do not have Heterozygote carriers (Hh) do not have

disorder and are resistant to malariadisorder and are resistant to malaria8-10% of Africans (or descendants) are 8-10% of Africans (or descendants) are

carrierscarriers

More Autosomal RecessiveMore Autosomal Recessive

Page 17: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Sickle-Cell Anemia PhotoSickle-Cell Anemia Photo

Page 18: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Autosomal Dominant Autosomal Dominant DisordersDisorders

Neurofibromatosis (NF)Neurofibromatosis (NF)Could be “Elephant Man’s” disorderCould be “Elephant Man’s” disorderAs mild as tan spots on skinAs mild as tan spots on skinCould cause severe deformities, tumors, Could cause severe deformities, tumors,

even deatheven death1 in 3000 newborns1 in 3000 newbornsMutation on chromosome 17Mutation on chromosome 17

Page 19: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Huntington’s DiseaseHuntington’s DiseaseBrain cells degenerate, causing involuntary Brain cells degenerate, causing involuntary

muscle jerks, slurred speach, loss of balance, muscle jerks, slurred speach, loss of balance, mood swings, memory loss, incapacitationmood swings, memory loss, incapacitation

Progressive: eventually causes deathProgressive: eventually causes deathOnset: 35-45 years oldOnset: 35-45 years oldRepeated sequences of AGC on chromosome Repeated sequences of AGC on chromosome

44Diagnostic test available, but no cureDiagnostic test available, but no cureWould you want to know?Would you want to know?

Autosomal Dominant Autosomal Dominant DisordersDisorders

Page 20: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

X-Linked or Sex-Linked TraitsX-Linked or Sex-Linked Traits

Traits located on X ChromosomeTraits located on X ChromosomeMales have them more often than Males have them more often than

femalesfemalesThey only have one X chromosomeThey only have one X chromosome

Page 21: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

Colorblindness (3 types – Red/Green Colorblindness (3 types – Red/Green most common)most common)

X-Linked or Sex-Linked TraitsX-Linked or Sex-Linked Traits

Page 22: Human Genetic Disorders Biology. Genetic Testing Amniocentesis and Chronic Villi Sampling Amniocentesis and Chronic Villi Sampling Sample of amniotic

HemophiliaHemophilia1 in 1500 males1 in 1500 malesLack a blood clotting factorLack a blood clotting factorCan bleed to death from wounds or Can bleed to death from wounds or

bruises (internal bleeding)bruises (internal bleeding)Duchenne Muscular DystrophyDuchenne Muscular Dystrophy

1 in 5000 males1 in 5000 malesMuscular deterioration starts 3-5 years Muscular deterioration starts 3-5 years

oldoldWheelchair by 12, rarely survive past 20Wheelchair by 12, rarely survive past 20

X-Linked or Sex-Linked TraitsX-Linked or Sex-Linked Traits