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

2. 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

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

4. 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

6. Nondisjunction
Down Syndrome

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

8. Pedigrees
Symbols

10. Analyzing Pedigrees

11. 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

12. Polydactyl – Dominant Disorder

13. 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?

15. 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

16. 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