Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
3-11-11 IN What are the probabilities of a monohybrid cross between two heterozygous parents? Flower color R=red r=white 3-11-11 Through Quiz Part B page 434 Notes OUT Bunny/Meiosis worksheet QUIZ!!! 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. Pod color Green = G Yellow = g Pod shape Expanded = E Constricted= e Peas that are homozygous for both green and expanded are crossed with peas that have yellow, constricted pods Parent 1 Phenotype=Green, Expanded Genotype= GGEE Parent 2 Phenotype= Yellow, Constricted Genotype= ggee Through Meiosis, what are all the possible gametes produced by the parents? Parent 1 G G E E GE GE GE GE Parent 2 ge g g ge e ge To do a Dihybrid cross 1. Find possible gametes 2. Create a 4X4 table 3. Plug in gametes 4. Find offspring possibilities e ge GE Dihybrid cross F1 Generation GE GE GE GgEe GgEe GgEe GgEe GgEe GgEe GgEe GgEe ge GgEe GgEe GgEe GgEe ge GgEe GgEe GgEe GgEe ge ge Results for possible offspring for F1 generation 16 / 16 100%: Phenotype- Green, Expanded Genotype- GgEe Carriers To find a F2 generation, take two offspring and cross them. What are possible gametes for the F2 generation for each parent? Parent 1---- GE, Ge, gE, ge Parent 2---- GE, Ge, gE, ge Complete the cross of the F2 Generation GE GE Ge gE ge Ge gE ge GGEE GGEe GgEE GgEe GGEe GGee GgEe Ggee GgEE GgEe ggEE ggEe GgEe Ggee ggEe ggee 3. From the F2 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 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 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 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. Short hair is a dominant trait for guinea pigs. Both parents are heterozygous. Complete a monohybrid cross for F1 generation. What is the probability that their offspring will have long hair? S s S SS Ss s Ss ss 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. Notes: Linkage - genes that are on the same chromosome end up together in the same gamete. 1. Suppose the genes for pod color and pod shape are on the same chromosome. G= green pod g=yellow pod E= Expanded pod e=constricted pod Parent 1 GGEE Gametes GE/ GE/ Parent 2 ggee Gametes ge/ ge/ In this case, the green, expanded produce only GE/ gametes and the yellow constricted produce only ge/ gametes. The slash represents the linkage F1 GE/ ge/ ge/ GE/ GE/ge GE/ge GE/ge GE/ge Combine the gametes of two from the F1 generation to find the F2 generation. F2 GE/ GE/ ge/ ge/ GE/GE GE/ge GE/ge ge/ge Using linkage, what would be the predicted phenotypes of the F2 generation? 75% green,expanded 25% yellow, constricted 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. PART D X-Linked Traits In fruit fly, Drosophilia melanogaster, red eye color is dominant over white eye color. R-red r-white Predict the genotypes and phenotypes you would expect in the F1 generation when a homozygous red-eyed female fly is mated with a white-eyed male fly. Homozygous red-eyed female RR genotype White-eyed male rr genotype R r r Predictions: 100% Rr genotype 100% Red-eyed offspring R Rr Rr Rr Rr 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 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 Xr, and the allele for red eyes by XR. 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. Male --- red-eyed XRY Female --- white-eyed XrXr Xr XR Y Xr XRXr XRXr Xr Y XrY Predictions: Phenotypes 50% male 50% female 100% red-eyed female 100% white-eyed male Diagram the cross that would result if the F1 offspring were mated to create the F2 generation. Show the genotypes and phenotypes of the new offspring. Male ---- XrY Female ---- XRXr Xr Y XR XRXr XRY Xr XrXr XrY Predicted outcomes: Genotypes 25% XRXr, 25% XrXr, 25% XRY, 25% XrY Phenotypes 50% females red-eyed, 50% females white-eyed, 50% males red-eyed, 50% males white-eyed