University:
Amherst College
Course:
BIOL 191 | Molecules, Genes and Cells
Academic year:

2010
Views:

118

Pages:

8
Author:

Ayden Decker

Chemical Biology 03 Dec 9, 2009 Inheritance III-cont. Continue with analysis of two-gene studies: Probabilities Punnett Square Branch Daigram Introduction to Pedigree Analysis! tracing the inheritance patterns of human disorders ~10,000 known single-gene human traits see OMIM (Online Mendelian Inheritance in Man) most are rare* genetic diseases allele causing disorder can be recessive OR dominant Albinism Cystic fibrosis Sickle cell anemia Tay Sachs disease Thalassemia * rare = incidence of disease is <1% Huntington’s Disease Achondroplasia Marfan Syndrome Brachydactyly Polydactyly Inheritance of albinism Recessive traits •unaffected parents of affected children are carriers •unaffected parents may have affected children •all the children of two affected individuals are affected •often appears to “skip a generation” Inheritance of albinism Aa aa or Aa aa ? Aa or AA •Who can be identified as a carrier? •What is the genotype of the monozygotic twins? •If the two-carrier couple have another child - what is the chance of that child being albino? •For rare diseases, we can assume that an unrelated individual is not a carrier. ex. the mom of the 3 carrier siblings is assumed to be homozygous dominant since Albinism is not common Aa x Aa 1 : 2 : 1 AA: Aa: aa or rare recessive disorders often show up in consanguinous matings Dominant traits •appears in every generation (cannot skip!) •at least one parent of an affected child is affected •two affected parents may have unaffected children •an affected parent will transmit the trait to 1/2 progeny •no “carriers” •can they be lethal? some pedigrees can be inconclusive

Chemical Biology 03 Inheritance II Abstract Concept and Behavior of Genes

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