GENETIC GENETIC DISORDERDISORDER

SSSBI3USBI3U

HEREDITARY DISORDERS (nature) - genetic HEREDITARY DISORDERS (nature) - genetic abnormalities caused by abnormalities caused by

recombination recombination

aneuploidy, sex-linked, nondisjunctionaneuploidy, sex-linked, nondisjunctionCONGENITAL DEFECTS (nurture) - CONGENITAL DEFECTS (nurture) - abnormalities abnormalities caused by embryonic caused by embryonic and/or and/or developmental developmental anomaliesanomalies

cleft lip/palate, conjoined, fetal alcohol cleft lip/palate, conjoined, fetal alcohol syndromesyndrome

ALBINISALBINISMMAutosomal Autosomal

recessiverecessiveLack of melanin Lack of melanin

pigmentpigment

Panamanian tribePanamanian tribe

““MoonMoon children” children”

CHROMOSOME DELETIONCHROMOSOME DELETION

Chromosome 2 - short Chromosome 2 - short armarm

Physical challengesPhysical challenges

Limited mental Limited mental developmentdevelopment

Decreased vision Decreased vision acuityacuity

Most chromosome Most chromosome deletions result in deletions result in spontaneously spontaneously aborted pregnanciesaborted pregnancies

SEX CHROMOSOME SEX CHROMOSOME ABNORMALITIESABNORMALITIES

XYXY Genotypic maleGenotypic male

XXXX Genotypic femaleGenotypic female

XOXO Turner’s Syndrome - Turner’s Syndrome - nondisjunctionnondisjunction

XXYXXY Klinefelter’s Syndrome - Klinefelter’s Syndrome - nondisjunctionnondisjunction

XYY “Super” male - nondisjunctionXYY “Super” male - nondisjunction

TURNER’S TURNER’S SYNDROMESYNDROME

XOXO

Two sets of autosomes but Two sets of autosomes but only one sex chromosomeonly one sex chromosome

97% spontaneous abortions97% spontaneous abortions

Female - short and sexually Female - short and sexually undeveloped (infertile)undeveloped (infertile)

Webbing of the neckWebbing of the neck

Wide chest with broadly Wide chest with broadly spaced nipplesspaced nipples

Narrowing of the aortaNarrowing of the aorta

KLINEFELTER’S KLINEFELTER’S SYNDROMESYNDROME

XXYXXY

Phenotype is not strikingly Phenotype is not strikingly different form XY and not different form XY and not apparent until after pubertyapparent until after puberty

Extremities are longerExtremities are longer

50% develop breasts50% develop breasts

Body hair is sparse (female Body hair is sparse (female pattern)pattern)

Somewhat mentally disadvantagedSomewhat mentally disadvantaged

Nondisjunction oogenesis (XX + Y)Nondisjunction oogenesis (XX + Y)

XXXXY - A rare form of Klinefelter’sXXXXY - A rare form of Klinefelter’s

Pentasomy 2N + 3 (autosomal = Pentasomy 2N + 3 (autosomal = lethal)lethal)

PolyploidyPolyploidy

Mental deficiencyMental deficiency

Facial abnormalitiesFacial abnormalities

Genital abnormalitiesGenital abnormalities

POLYPLOIDY - SemilethalPOLYPLOIDY - SemilethalMosaic of two cell types - Mosaic of two cell types -

tetraploid (XXYY) and diploid tetraploid (XXYY) and diploid (XY)(XY)

The child died at nine The child died at nine months.months.

TETRAPLOIDTETRAPLOIDCranial bone abnormalities, ocular anomalies & Cranial bone abnormalities, ocular anomalies &

facial cleftsfacial clefts

Enlarged placentaEnlarged placenta

Spleen, heart, kidneys, adrenal glands, brain Spleen, heart, kidneys, adrenal glands, brain anamoliesanamolies

Aneuploidy Aneuploidy

One to a few chromosomes are lost or One to a few chromosomes are lost or added to a normal set or added to a normal set or nondisjunction (irregular distribution nondisjunction (irregular distribution of sister chromatids (mitosis) or of sister chromatids (mitosis) or homologues (meiosis)homologues (meiosis)Nullisomy - loss of one homologous pair Nullisomy - loss of one homologous pair 2N - 22N - 2Monosomy - loss of a single chromosome Monosomy - loss of a single chromosome 2N - 12N - 1Trisomy - single extra chromosome; threeTrisomy - single extra chromosome; three

copies of one chromosome type 2N copies of one chromosome type 2N + 1+ 1

Tetrasomy - an extra pair; four copies of oneTetrasomy - an extra pair; four copies of one

chromosome pair 2N + 2chromosome pair 2N + 2

Trisomy 21 Trisomy 21 Down’s SyndromeDown’s Syndrome

Trisomy - single extra chromosome; threeTrisomy - single extra chromosome; three

copies of one chromosome type 2N + 1copies of one chromosome type 2N + 1

Low IQ (variable)Low IQ (variable)

Epicanthal folds over eyesEpicanthal folds over eyes

Short - broad hands with Short - broad hands with the simian line across the the simian line across the palmspalms

Below-average heightBelow-average height

ICHTHYOSIS CONGENITA ICHTHYOSIS CONGENITA Brittle, leathery skin with deep Brittle, leathery skin with deep bleeding fissuresbleeding fissures

A recessive lethal allele with no A recessive lethal allele with no obvious heterozygous phenotype.obvious heterozygous phenotype.

Similar in transmission to Tay-Similar in transmission to Tay-Sachs and Cystic fibrosisSachs and Cystic fibrosis

NEUROFIBROMYLEYISNEUROFIBROMYLEYIS - von Recklinghausen - von Recklinghausen diseasedisease

Tumours in the central and peripheral Tumours in the central and peripheral nevous systemnevous system

Variable expressivity - Variable expressivity - degree of phenotype degree of phenotype variesvaries

““Elephant Man” - John Merrick - London Hospital Elephant Man” - John Merrick - London Hospital 18861886

MARFAN MARFAN SYNDROMESYNDROMEA dominant collagen A dominant collagen disorderdisorder

Affects eyes, CV system, Affects eyes, CV system, and the musculoskeletal and the musculoskeletal systemsystem

The silent killer The silent killer

SEX - LINKED DISORDERSSEX - LINKED DISORDERS

HEMOPHILIAHEMOPHILIA

The Royal DiseaseThe Royal Disease

Colour blindnessColour blindness

CONJOINED CONJOINED TWINSTWINSAn improper division of cells An improper division of cells thought to occur thought to occur embryonically somewhere embryonically somewhere between morula to blastula between morula to blastula stagestageAn environmental An environmental component?component?