Chapter 14 HO

gangliosidesaremadeandbrokendownrapidlyinearlylifeast

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Unformatted text preview: ul!lipid!called!ganglioside*GM2!in! %ssues!and!nerve!cells!in!the!brain!!! ! This is caused by insufficient activity of an enzyme called beta-hexosaminidase A that catalyzes the biodegredation of glangliosides ! ! Gangliosides!are!made!and!broken!down!rapidly!in!early!life!as!the!brain!develops!! ! ! ! :( Symptoms$in$infants$with$TaybSachs$disease:$ The lipids build up in the NERVE CELLS and start to cause horrible problems…. Child!appears!to!develop!normally!for!the!first!few!months!of!life! However,!as!nerve!cells!become!distended!with!fady!material,!a!relentless!deteriora%on!of! mental!and!physical!abili%es!occurs! The!child!becomes!blind,!deaf,!and!unable!to!swallow!! *! Muscles begin to atrophy and paralysis sets in Neurological!symptoms!include!demen%a!and!seizures! The!child!usually!dies!within!a!few!years! hdp://www.curetayVsachs.org/about.shtml! Inheritance:$$TaybSach$Disease$ Autosomal RECESSIVE. What does autosomal mean? It's located on chromosomes 1-22….NOT on the 23rd (thats a sex chromosome) LOCATED ON CHROMOSOME 15. Both MOTHER and FATHER must carry the recessive allele. Organismal$level:$ 25% unaffected Biochemical$Level:$$ Beta0hexosaminidase*A** enzyme*ac8vity* this appears incomplete dom. Molecular$Level:$$ Type*of*Beta0 hexosaminidase*molecules*** this appears codominance. High! 50% carrier In!between! 25% chance of being affected :( Low! (enough!to!prevent!disease)! so they won't make as much as someone with two dominant alleles but enough to stay healthy…..THIS SUGGESTS INCOMPLETE DOMINANCE !!!!!!!!!!!!!!!!!! Normal! Normal! !Dysfunc%onal! !!!!!!!!!! Normal! !Dysfunc%onal! Dysfunc%onal! CO-DOMINANCE!!! B/c both NORMAL and DYSFUNCTIONAL enzymes are made! Frequency$of$Dominant$Alleles$in$a$Popula/on:$ ! Are$dominant$alleles$more$prevalent$in$a$popula/on$than$recessive$alleles?$ ! NO! DOMINANCE DOES NOT NECESSARILY MEAN PREVALENCE!!! $$! Something can be dominant and NOT common or even benificial. ! Example:$$$Polydactyl$ ANOTHER EX: Huntington's Disease ! ! In!some!cases,!polydactyl!is!caused!by!the!presence!of! a!dominant!allele! ! 1!in!400!babies!are!born!with!an!extra!finger!or!toe! ! Why$do$so$few$people$suffer$from$this$disorder?$ ! Mul/ple$Alleles:$ Most genes have multiple alleles ! Example:!!ABO!blood!group!–!three!alleles!(O,!A,!and!B)!! RBC!had!an!integral!protein!with!a!long!chain!of!carbohydrates!adached!to!the!protein! Each!allele!codes!for!an!enzyme!that!adds!(or!does!not!add)!a!specific!monosaccharide!to!the! end!of!the!the!carbohydrate!chain!! !! ! Type!O!–!no!extra!monosaccharide! GalNAc) Galactose) RBC$ ATAn<gen) BTAn<gen) Type)AB) Type!A!–!GalNAc!monosaccharide! Type!B!–!Galactose!monosaccharide! GalNAc) Type!AB!–!Both!GalNAcVending!and! Galactos...
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This document was uploaded on 02/04/2014.

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