1. Sex Determination In humans, the X and Y chromosomes control the sex of offspring. Outcome is always 50% chance of a male, and 50% chance of a female Female sex chromosomes: XX Male sex chromosomes: Xy

2. Practice Problem  The Jones family is planning to have another child. Mrs. Jones is the proud mom of 3 healthy boys. In her heart, she has always wanted a daughter. What are her chances of her next baby being a girl? Show with a Punnett square. X y X X y 50% chance girl 50% chance boy

3. Pedigree Charts The family tree of genetics

4. What is a Pedigree? A pedigree is a chart of the genetic history of family over several generations.A pedigree is a chart of the genetic history of family over several generations. Scientists or a genetic counselor would find out about your family history and make this chart to analyze.Scientists or a genetic counselor would find out about your family history and make this chart to analyze.

5. Constructing a Pedigree  Male  Female

6. Connecting Pedigree Symbols  Parents  Siblings Examples of connected symbols:

7. Example  What does a pedigree chart look like?

8. Symbols in a Pedigree Chart  Affected  “Normal”  Deceased

9. Interpreting a Pedigree Chart Determine whether the disorder is dominant or recessive. –If the disorder is dominant, one of the parents must have the disorder. –If the disorder is recessive, neither parent has the disorder because they can be heterozygous.

10. Example of Pedigree Charts  Dominant or Recessive?

11. Answer  Dominant

12. Example of Pedigree Charts  Dominant or Recessive?

13. Answer  Recessive

14. Summary  Pedigrees are family trees that explain your genetic history.  Pedigrees are used to find out the probability of a child having a disorder in a particular family.  To begin to interpret a pedigree, determine if the disease or condition is autosomal or X- linked and dominant or recessive.

15. I II III IV 1 1 1 1 2 2 2 23 3 34 4 1. What is the genotype of IV-1? 2. What is the genotype IV-3? 3. What is the genotype of III-1? 4. What is the genotype III-2? 5. What is the genotype II-3? 6. Is it possible for individual IV-2 to be a carrier? Why? Let H= hitchhiker’s thumb h= straight thumb

16. 7.Which members of the family above are afflicted with sickle cell anemia? 8. How are individuals III-4 and III-5 related? 9. How are individuals I-1 and I-2 related? 10. How are individuals II-7 and III-2 related? 11. How are individuals I-2 and III-5 related? 12. How many children did individuals I-1 and I-2 have? 13. How many girls did II-1 and II-2 have? How many have sickle cell anemia? 14. Label the genotype for: II-1 _______ II-2 _______ II-6 ________ II-7 ________ II-8 _______ III-1_______ III-3 _______ Let D= normal d=- sickle cell