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Transcript of Sims genetics
15How many autosomes:? 22 pair How many sex chromosomes?1 pairFemales: 46 XX Males:46 XY16Normal human karyotype isDiploid.
Sperm/ Eggs are Haploid (carry one copy of each chromosome).
The sex of newborn is determined by Sperm17 GENETIC ENVIRONMENTALHemophiliaOsteogenesis imperfectaPhenylketonuriaGalactosaemiaDuchene muscular dystrophySpina bifidaIschemic heart diseaseAnkylosing spondylitisScurvyTraumaTuberculosisPeptic ulcerDiabetes mellitus18*HEREDITARY: Transmitted in the germ line; passed from parents to their offspring.
*FAMILIAL: Diseases run in families and represent multifactorial inheritance. Risk for first degree is 5-10% higher.
*CONGENITAL: Born with; disease present since birth. 194BARR BODY [ SEX CHROMATIN ]NucleusBarr body# of Barr bodies = # of X chromosomes - 120
30LYON HYPOTHESIS: [ 1961, Mary Lyon ] 1. Only one of the X - chromosomes is genetically active, 2. Other X of either maternal or paternal origin undergoes heteropyknosis and is rendered inactive.31 3. Inactivation of either the maternal or paternal X occurs at random among all the cells of the blastocyst on or about the 16th day of embryonic life.
4. Inactivation of the same X chromosome persists in all the cells derived from each precursor cell.LYON HYPOTHESIS:32DOWN SYNDROME33INCIDENCE: 1 in 800 live births [ overall ] Maternal age: < 20 yrs - 1 in 1550,> 45 yrs - 1 in 3034
Flat faceProtruding tongueOcciput tends to be flatLow bridged noseOblique palpabral fissureEpicanthic foldsSlanting eyesBrushfield spots in iris
42 40%- Congenital cardiac defects ASD, VSD, TOF, PDA. 10-20 fold risk to develop Acute leukemia's: ALL/AML. CNS: Mental retardation, IQ -30. Develop Alzheimers disease - -- at very young age; Intestine: Imperforate anus, duodenal stenosis, Hirschsprungs disease.Sterility: Arrested spermatogenesis.43Life expectancy: Most common cause of death:Congenital heart diseases and leukemia.With normal heart, only 5% of children with Down syndrome die before age 10.
After age 10, the estimated life expectancy is 55 years.44KLINEFELTER SYNDROME45Common cause of male hypogonadism and infertility.1 in 1000 live male births,Presence of one or more extra X chromosome, 47 XXY. Rarely diagnosed before puberty,
46Clinical features: Eunuchoid body habitus:Long legs, tall and thin. Small, atrophic testes, small penis. Lack of secondary sexual characteristics, Deep voice of high pitch. Gynecomastia, feminine characters. IQ - low; mental retardation, behavioral abnormality.47
Karyotype of KFS50TURNER SYNDROME51Turner Syndrome:Most common sex chromosome abnormality in females,Monosomy X; the missing chromosome X is usually of paternal origin.Incidence: 1/8000 . Most die in infancy52
Karyotype of Turner Syndrome:53Clinical features of TS:Edema of dorsum of hand & foot,Bilateral neck webbing,Congenital heart diseases, (COA)Short stature, hyper convex finger nails.Broad chest & widely spaced nipples,Multiple Pigmented nevi,Amenorrhea [ Primary ],Infertility, streak ovaries. Low posterior hair line.Wide carrying angle (cubitus valgus).54
Cystic hygroma of neck > webbed neck57
Streak Ovaries Turners Syndrome58
Streak ovaries60True Hermaphrodite: ( ovary + testis )
Pseudo Hermaphrodite: ( Disagreement between phenotypic and gonadal sex )61
63Pseudo hermaphroditeFemale pseudo hermaphrodite: * Ovaries, * Male external genitalia,
Male pseudo hermaphrodite: .. Testes, .. Female external genitalia;
64MENDELIAN DISORDERS:[ MUTANT GENES WITHLARGE EFFECT ]Genetic diseases:6566
7576Class I Loss of receptor synthesisClass II Transport inside cell is impairedClass III Failure of receptors to bind LDLClass IV Fail to internalize after bindingClass V Internalized bodies are trapped in endosomes7677MUTATION IN ENZYME PROTEINPHENYLKETONURIAGALACTOSEMIALYSOSOMAL STORAGE DISEASESGLYCOGEN STORAGE DISEASES7778DISEASEENZYME DEFICIENCYPompes DiseaseLysosomal GlucosidaseTay Sachs diseaseHexosaminidase AGaucher diseaseGlucocerebrosidaseNiemann Pick diseaseSphingomyelinaseHurler diseaseL-IduronidaseHunter diseaseL-Iduronosulphate sulphatase7879