Download - Why are recessive disorders more common than dominant ones? Agenda 1.Genetic disorders 2.Pedigrees
Why are recessive disorders more common than dominant ones?
Agenda1.Genetic disorders2.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?Agenda1.Genetic Disorder Notes2.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?How are person II2 and II3 related?Agenda1.Pedigree Review2.Pedigree Practice3.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
Agenda1.Finish yesterday’s movie2.Lorenzo’s oil