Vision Collage of Medicine Lecture 23: The Patterns of Genetic Inheritance-1 PDF

The Patterns of Genetic 18 Inheritance-1 by Dr.Ezat Mersal  The Patterns of Genetic Inheritance  I. What is a pedigree?  A. Definition  B. Uses  II. Constructing a pedigree  A. Symbols  B. Connecting the symbols  III. Interpreti...

The Patterns of Genetic 18 Inheritance-1 by Dr.Ezat Mersal  The Patterns of Genetic Inheritance  I. What is a pedigree?  A. Definition  B. Uses  II. Constructing a pedigree  A. Symbols  B. Connecting the symbols  III. Interpreting a pedigree  Autosomal dominant Inheritance  The Patterns of Genetic Inheritance Mendelian Non-Mendelian Autosomal Dominant Imprinting Autosomal Recessive Mitochondrial X-linked Dominant Multifactorial X-linked Recessive Sporadic Y-linked Contiguous gene syndromes Non-penetrance Sex-limited/sex influenced New mutation Germline mosaicism Adult-onset conditions Anticipation Consanguinity Heterogeniety Interaction Pleiotropy © 2015 John Wiley & Sons, Inc. All rights reserved. A pedigree is: a chart of the genetic history of family over several generations.  It shows:  1. How traits are transmitted (causes of diseases)  2. Predictions of the probabilities of having an affected child  3. If the trait is dominant or recessive  4. If the gene is autosomal or X-linked © 2015 John Wiley & Sons, Inc. All rights reserved.  nortze 40 D -chrom - Proband (propositus) The first person with - =>linked disease who - presented to medical -80 attention. (index 9 1812 19;. case) Grey , s © 2015 John Wiley & Sons, Inc. All rights reserved. © 2015 John Wiley & Sons, Inc. All rights reserved.  &Sig & 91g9i/ ↑  Determine whether the disorder is dominant or recessive.  If the disorder is dominant, one of the parents must have the disorder. - -2 5 % %  If the disorder is recessive, neither parent has to have the disorder because they can be heterozygous. © 2015 John Wiley & Sons, Inc. All rights reserved.  ↑ =% esQ & I © 2015 John Wiley & Sons, Inc. All rights reserved. G © 2015 John Wiley & Sons, Inc. All rights reserved.  G © 2015 John Wiley & Sons, Inc. All rights reserved. 1) Transmission: Are there affected family members in every generation (vertical pattern) or in only a single generation (horizontal pattern)? 2) Sex Differences: What is the ratio of affected males to females? 3) Segregation: Is disease/gene being passed through unaffected females? Is there male to male transmission? What % of children are affected (e.g. all of sons but none of daughters)? © 2015 John Wiley & Sons, Inc. All rights reserved.   Character –heritable feature  Trait – each variant for a character  Monohybrid cross – a cross that tracks the inheritance of a- single character  P generation – (parental). MCQ F1- (first filial) offspring of P generation  F2 – (second filial) offspring from F1 cross  Punnett square shows that affected parent either passes a normal or disease gene to the offspring © 2015 John Wiley & Sons, Inc. All rights reserved.  Allele- alternate version of a gene is d'y bil homo-  Dominate allele – expressed in the heterozygote Gzygote  Recessive allele – not expressed in the heterozygote  Homozygote – pair of identical alleles for a character Homozygous dominant- BB Homozygous recessive - bb  Heterozygote – two different alleles for a character (Bb)  Genotype – genetic makeup  Phenotype – appearance of an organism © 2015 John Wiley & Sons, Inc. All rights reserved. Autosomal dominant inheritance occurs when one copy of an allele is sufficient for expression of a trait and the gene is located on one of the 22 autosomes. © 2015 John Wiley & Sons, Inc. All rights reserved.  Vertical pattern: multiple generations affected.  Males and females equally likely to be affected  See male to male transmission  All affected individuals should have an affected parent.  Unaffected individuals do not pass on the gene  Both sexes should be equally affected.  Roughly 50% of the offspring of an affected individual should also be affected.  Huntington’s disease, Achondroplastic dysplasia, Neurofibromatosis. © 2015 John Wiley & Sons, Inc. All rights reserved.  Vertical pattern: multiple generations affected Males and females equally likely to be affected See male to male transmission Each child of an affected individual has a 50% chance to be affected Unaffected individuals do not pass on the gene Every affected child has an affected parent © 2015 John Wiley & Sons, Inc. All rights reserved.  Basic genetics : a human approach / BSCS. Dubuque, IA, Kendall/Hunt Pub. Co., c1999. 147 p. QH431.B305 1999  Genes, ethnicity, and ageing. Edited by Lincoln H. Schmitt, Leonard Freedman, Rayma Pervan. Nedlands, Australia, Centre for Human Biology, University of Western Australia ; Singapore, River Edge, NJ, World Scientific, c1995. 100 p.QH455.G45 1995  Genetic polymorphisms and susceptibility to disease. Edited by M. S. Miller and M. T. Cronin. New York, Taylor & Francis, 2000. 266 p.