genetic disorders sbi3u hereditary disorders (nature) - genetic abnormalities caused by...
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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?