(12) A breeder of pet fur flops has a cage of fur flops that often produces indi

Question

(12) A breeder of pet fur flops has a cage of fur flops that often produces individuals with exceptionally long and tall ears. There is a new mutation in his crop of flops. He crosses one of his long eared males to a normal female, and he gets the following litter of fur flops: 16 long-cared males 15 long-eared females 17 normal males 16 normal females a) Would you describe this as more like a "self cross" or a "test cross"? b) What ratios do you see in this litter? (2 points) (1 point) c) What does the result of this cross suggest about the long-eared allele? What genotypes would you suspect these animals have? (Explain your notation for alleles.) (3 points) Your friend likes the look of long ears on the fur flops, so he decides to work towards having a pure-breeding strain of long-eared fur flops. He crosses a long-eared male to a long- eared female from the previous litter. Here is the resulting litter of fur flops from this cross: 18 long-eared males 17 long-eared females 8 normal males 9 normal females d) What ratio do you see in this litter? (2 points) e) What does this result suggest about genotype and phenotype of the progeny? (2 points) f) How would you advise your friend to proceed in his plan to obtain a pure-breeding strair of long-eared fur flops? What would be the next step that he should take? (1 point)

Explanation / Answer

Please find the answers below:

Answer 1:

Part a) According to the information, the ratio of the flocks after the mutational cross is nearly 1:1:1:1 which follows the non-random observation of typical Mendelian pattern of inheritance of test-cross in which a single trait is involved, irrespective of the sexes of the offpsrings. This could have been a self-cross if the ratio would have been 9:3:3:1 for a dihybrid cross.

Part b) As it can be seen clearly from the data, the ratio for different phenotypes are given by 1:1:1:1.

Part c) As it could be seen that the present cross is a test-cross at single location, one can assume that the cross is made between a heterozygous parent and a recessive homozygous parent from the previous generation so that the desired ratio fo 1:1:1:1 for males and females could be obtained. Thus, if we denote the trait by AA in dominant parent, the heterozygous parent would be given by Aa and the recessive parent would be given by aa. Thus, the cross has been made between Aa and aa.

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