4 The breeder from 2 purchases seeds of a different strain of rice that has the

# 4 the breeder from 2 purchases seeds of a different

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4. The breeder from #2 purchases seeds of a different strain of rice that has the same yield as his strain and crosses it to his strain of rice. The F1 from this cross has the same yield as both parental strains, but by selection in the F2 and F3 he is able in a few generations increase the yield considerably. Explain how this is possible. Give examples of genotypes for the strains and the F1 Since the F1 yield is the same as that of the two parental strains, all three populations must contain the same number of contributers. Those in the parental strains are homozygous (but for different genes) and those in the F1 are heterozygous. From the F2 and F3, the farmer is able to select for seeds with a higher number of contributers. For example Parental strains AA BB CC dd ee ff x aa bb cc DD EE FF (each with 6 contributers) F1 Aa Bb Cc Dd Ee Ff (the F1 has 6 contributers) F2 segregation would produce some plants with 7-12 contributers and would produce a higher yield. #5) a) How many genotypes are possible for an autosomal gene with 6 alleles. (If you use a formula that you learned in mathematics, be careful, you may get an answer that is double. Remember that A1A2 and A2A1 are the same genotype) A1A1, A1A2, A1A3, A1A4, A1A5, A1A6, A2A2, A2A3, A2A4, A2A5, A2A6 A3A3, A3A4, A3A5, A3A6 A4A4, A4A5, A4A6 A5A5 A5A6 A6A6 6 + 5 + 4 + 3 + 2 + 1 =21 21 (there are 6 homozygotes and 15 heterozygotes) b) How many genotypes are possible for an X-linked gene with 6 alleles 27 (21 for females as shown above and 6 hemizygous male genotypes).

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#6 A species of tiny antelope, known as the zephyr, has an XY system of sex determination, similar to mammals. Zephyr males have small antlers and females do not. The antlers can be two pronged (2-pr) or three pronged (3-pr) and this is determined by a single gene which is found on the X chromosome (there is no allele for 2-3 pronged on the Y chromosome). In a large population, 74% of the adult males have two-pronged antlers and the rest of the adult males have three pronged antlers. a) What is the frequency of the three pronged allele in the adult male population? The frequency of the 3-pronged allele is 26%. b) Show the F1 and F2 of a cross between a 2-pronged male with a female from a true breeding 3- pronged strain. Use the symbols given in the P cross. Give genotypes and phenotypes for all progeny of the cross.
• Spring '11
• dr
• Genetics, 2m, VE, heterozygote, 20g

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