1. 3-11-11  IN  What are the probabilities of a monohybrid cross between two heterozygous parents?  Flower color R=redr=white

2. 3-11-11  Through  Quiz  Part B page 434  Notes  OUT  Bunny/Meiosis worksheet

3. QUIZ!!!

4. Two Mendelian Traits: Pea Pod color and Shape  Dihybrid cross -- A genetic cross between individuals differing in two alleles  In garden peas, the genes for the traits of pod color and pod shape are on different chromosomes.

5.  Pod color  Green = GYellow = g  Pod shape  Expanded = EConstricted= e  Peas that are homozygous for both green and expanded are crossed with peas that have yellow, constricted pods

6.  Parent 1  Phenotype=Green, Expanded  Genotype= GGEE  Parent 2  Phenotype= Yellow, Constricted  Genotype= ggee

7.  Through Meiosis, what are all the possible gametes produced by the parents?  Parent 1 G G E E  GEGEGEGE

8.  Parent 2 g gee  gegegege  To do a Dihybrid cross  1. Find possible gametes  2. Create a 4X4 table  3. Plug in gametes  4. Find offspring possibilities

9. Dihybrid cross F 1 Generation GE ge GgEe ge

10. Results for possible offspring for F 1 generation 16 / 16 100%: Phenotype- Green, Expanded Genotype- GgEe Carriers

11.  To find a F 2 generation, take two offspring and cross them.  What are possible gametes for the F 2 generation for each parent?  Parent 1---- GE, Ge, gE, ge  Parent 2---- GE, Ge, gE, ge

12. Complete the cross of the F 2 Generation GGEEGGEeGgEEGgEe GGEeGGeeGgEeGgee GgEEGgEeggEEggEe GgEeGgeeggEeggee GEGe gEge

13.  3. From the F 2 generation, what fraction would you predict to have each of the following phenotypes?  A. The dominant phenotype for pod color and pod shape.  9 / 16  B. The dominant phenotype for pod color and recessive phenotype for pod shape.  3 / 16

14.  C. The recessive phenotype for pod color and the dominant phenotype for pod shape.  3 / 16  D. The recessive phenotype for pod color and pod shape.  1 / 16

15.  4. If there were 288 offspring, how many would you predict to be:  Green, Expanded?  162  Green, Constricted?  54  Yellow, Expanded?  54  Yellow, Constricted?  18

16. Actual Results  Green, expanded=165  Green, constricted= 51  Yellow, expanded=56  Yellow, constricted=16  A. Do the results match your predictions?  B. Explain why they don’t match.

17.  Short hair is a dominant trait for guinea pigs. Both parents are heterozygous.  Complete a monohybrid cross for F 1 generation.  What is the probability that their offspring will have long hair? SSSs ss Ss SsSs

18. Part C Linked-Traits  Many different genes are located on the same chromosome.  When gametes are formed, alleles of genes that are located on the same chromosome end up together in the same gamete.

19.  Notes:  Linkage - genes that are on the same chromosome end up together in the same gamete.

20.  1. Suppose the genes for pod color and pod shape are on the same chromosome.  G= green pod g=yellow pod  E= Expanded pode=constricted pod  Parent 1 GGEE  Gametes GE/GE/  Parent 2 ggee  Gametes ge/ge/

21.  In this case, the green, expanded produce only GE/ gametes and the yellow constricted produce only ge/ gametes.  The slash represents the linkage GE/ge GE/ ge/ F1F1

22.  Combine the gametes of two from the F 1 generation to find the F 2 generation. GE/GEGE/ge ge/ge GE/ ge/ F2F2

23.  Using linkage, what would be the predicted phenotypes of the F 2 generation?  75% green,expanded  25% yellow, constricted

24. Notes:  Crossing-over - During meiosis, it is the breakage and exchange of corresponding segments of chromosome pairs.  Watch DVD “Crossing-over”  Describe the effect that crossing over might have on results.

25. PART D X-Linked Traits  In fruit fly, Drosophilia melanogaster, red eye color is dominant over white eye color.  R-redr-white  Predict the genotypes and phenotypes you would expect in the F 1 generation when a homozygous red-eyed female fly is mated with a white-eyed male fly.

26.  Homozygous red-eyed female  RR genotype  White-eyed male  rr genotype Predictions: 100% Rr genotype 100% Red-eyed offspring Rr R r

27.  2. Actual results  Based on 139 offspring, all had red eyes  3. Next, you mated a red-eyed male flies with white-eyed female flies.(reciprocal cross) Would you expect similar results?  4. In the early 1900’s, biologist Thomas Hunt Morgan performed a similar cross. But, instead of getting all red-eyed flies, he got half red-eyed flies and half white-eyed flies. However, all the red-eyed flies were females, and all the white-eyed flies were males. How might you explain these seemingly unexpected results?  Read Need to know on page 436

28.  5. A. A superscript letter designates the allele. Often it is used with the chromosome symbol to diagram a cross of a trait that is carried on the X chromosome. For example, the allele for white eyes might be represented by X r, and the allele for red eyes by X R. The symbol Y can represent the Y chromosome and does not carry a gene for eye color. Using these symbols, diagram the cross described in Step 3. Show the expected genotype and phenotype fractions.

29.  Male --- red-eyed XRYXRY  Female --- white-eyed XrXrXrXr  Predictions:  Phenotypes 50% male 50% female  100% red-eyed female  100% white-eyed male XRXrXRXr XRXrXRXr XrYXrYXrYXrY XrXrXrXr XRYXRY

30.  Diagram the cross that would result if the F 1 offspring were mated to create the F 2 generation. Show the genotypes and phenotypes of the new offspring.

31.  Male ---- X r Y  Female ---- X R X r  Predicted outcomes:  Genotypes 25% X R X r, 25% X r X r, 25% X R Y, 25% X r Y  Phenotypes 50% females red-eyed, 50% females white-eyed, 50% males red-eyed, 50% males white-eyed XRXrXRXr XRYXRY XrXrXrXr XrYXrY XrYXrY XRXrXRXr