Chromosomal Abberations PDF
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Uploaded by FreshestYeti
Faculty of Physical Therapy - MSA University
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Summary
This document provides a detailed overview of chromosomal aberrations. It describes different types such as deletion, duplication, inversion, and translocation. Understanding their mechanisms and consequences is crucial in medical genetics.
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Chromosomal abberations Definition Deviation from normal NO. Or str of chr Commonly Cause MR & developmental R strucural aberrations= mutation Inf Viral irradiation Balanced ab = Insecticides chr has normal Drugs genetic information...
Chromosomal abberations Definition Deviation from normal NO. Or str of chr Commonly Cause MR & developmental R strucural aberrations= mutation Inf Viral irradiation Balanced ab = Insecticides chr has normal Drugs genetic information unbalanced ab = chr miss genetic information strucural abberations types 1- Break Heal by reunion of sticky ends strucural abberations types 2- Deletion = Loss of fragmented part terminal interstitial ring 1 br+ loss 2 br+ from 1 end loss of sgment in between: 2 br+ loss+ reunion in a ring Wolf s= deletion of short arm of chr 4 Cri du chat s= deletion of short arm of chr 5 strucural abberations types 3-Duplication Addition of extra piece of homologous chr due to unequal crossing over → 2 copies of same gene on chr strucural abberations types 4- Inversion 2 breaks + reunion in inverted form:- Peri centric: break on both sides of centromere Para centric: break on one side strucural abberations types 5- Transfere of chr segment Translocation to non homologous chr t 14 21 a) Robersonian TL= Centric fusion: In acrocentric chr 14&21 Fusion of both long arms→ chr t Loss both short arms( insignificant) 3-4% of cases of Down s. N.B IF a parent is a carrier of chr 21 translocation The risk of having Down child is up to 100% b) Reciprocal translocation: Transfere of chr segment to non homologous chr Its balanced as no genes are lost or added If chr 22&9 = philadelphia chr Diagnostic of CML strucural abberations types 6-Isochromosomes TS division of chr during anaphase of mitosis 2 non similar chromatids 2 non similar chromsomes 1 has 2 long arms & 1 has 2 short arms In submetacentric chr