Why are recessive disorders more common than dominant ones? Agenda Genetic disorders Pedigrees

What are the chances of 2 carriers of cystic fibrosis will have a child with CF? The odds of one carrier (1/23.6) marrying another carrier (1/23.6) is 1/500 The occurrence of CF is about 1/2000

How can we see the prevalence of a trait in a family over a long period of time? Agenda Genetic Disorder Notes Pedigrees

Nondisjunction Cell division chromosomes separate Nondisjunction occurs when chromosomes fail to separate More chromosomes than usual Trisomy – set of three chromosomes of one kind Monosomy – set of 1 chromosome

Nondisjunction Down Syndrome

Pedigrees Pedigree – diagram that traces the inheritance of a particular trait through several generations

Pedigrees Symbols

Analyzing Pedigrees

Inferring Genotypes Use pedigrees to infer genotypes Determine genotype from phenotype Dominant traits are easier to identify dominant traits are exhibited in the phenotype If good records have been kept you can predict disorders in future offspring

Polydactyl – Dominant Disorder

Questions Is this trait dominant or recessive? Explain your answer. Name the 2 individuals that were carriers of hemophilia How are individuals III-1 and III-2 related? How many children did individuals I-1 and I-2 have How many girls did II-1 and II-2 have? How many have hemophilia?

Is this a recessive or dominant trait Is this a recessive or dominant trait? How are person II2 and II3 related? Agenda Pedigree Review Pedigree Practice Movie

Finish yesterday’s movie The pedigree to the right shows a family’s pedigree for colorblindness (a sex linked trait) Which sex can be carriers of colorblindness and not have it? Why does individual IV-7 have colorblindness?   Why do all the daughters in generation II carry the colorblind gene? IV Agenda Finish yesterday’s movie Lorenzo’s oil