Lesson 18 Using Punnett Squares and Pedigrees

1. B b B b Lesson 18 Using Punnett Squares and Pedigrees Bb x Bb male / sperm X BB Bb Remember this? female / eggs Bb bb

2. A Punnett Square is a diagram used to identify _____________ combinations resulting from a mating. This married couple is considering having their first baby. The man is heterozygous for a disease. The woman is also heterozygous for the disease.

3. The couple comes to you for counseling. They want you to tell them are the chances they will have a healthy baby.

4. You know that the disease they carry is a recessive trait and that both parents are heterozygous. RR Rr rr Which of the above genotypes will you need to use? __ __ Man x Woman __ ? __

5. __ __ Man x Woman ____ ____ __ Genotype % RR = Rr = rr = ___% ___% __ ___% Phenotype % Healthy = Carrier = Diseased = ___% ___% The chance that the couple will have a baby that has the disease is _____%. ___%

6. Who you are… _________________ ___Chromosomes

7. ___________ = family record for one specific trait. __________________ traits = genes for these traits are carried on the sex chromosomes. The gene for Red-Green _______ _______________is carried on the ___chromosome. Female must get ___(___) X’s to have colorblindness. Why are most sex-linked traits carried on the X chromosome? Male must get ___(__Y) X to have colorblindness.

8. Reading a Pedigree = female without trait = male without trait = female with trait = male with trait = male carrier = female carrier = two parents = three children Analyzing a Pedigree Interactive http://highered.mcgraw-hill.com/sites/0072485949/student_view0/chapter3/interactive_activity.html

9. Another view of a pedigree… This one is for Huntington’s Disease