Questions 5-6 are based on the information below: A student working in a genetic
ID: 203604 • Letter: Q
Question
Questions 5-6 are based on the information below: A student working in a genetics lab was given the task of studying a new Drosophila mutation called In the time allotted, they were only able to perform the crosses shown below. NOTE: E refers to the ebony phenotype and + refers to the wild type phenotype A wt male was crossed with an ebony female. Results of the cross: Offspring Phenotype Number Proportion Ratio Female: E 533 Male: E Total 0.4995 0.5005 1.000 1.002 534 1067 Next, starting with new flies (not FIs), an ebony male was crossed with a wt female. Results of the cross: Offspring Phenotype Number Proportion Ratio Female: E 500 Male: E Total 0.4970 0.5030 1.000 1.012 506 1006 Next, starting with new flies (not FIs), an ebony female was crossed with an ebony male. Results of the cross Offspring Phenotype Number Proportion Ratio 1.000 Female: E 480 497 977 0.4913 0.5087 1.035 Male: E Total 5) What is the genetic basis for the ebony mutation? Circle all that are true. a) ebony is dominant to the wild-type allele b) ebony is an X-linked allele c) ebony is a lethal allele 6) Using Drosophila nomenclature, which symbols correctly represent the ebony and wild-type alleles for this gene? a) E: ebony; E: wild-type b) E: ebony: E: wild-ope c) et:ebony; e: wild-type d) e:ebony e:wild-typeExplanation / Answer
5) Answer: A) Ebony is dominant to the wild type
If ebony was the lethal allele, any individual carrying the ebony allele would be dead. Also, if ebony was X linked, then, when in the second cross, male and female were exchanged, the results would be different.
6) Answer: B) E: ebony; E+ : wild type
Wild type is always denoted with a super script + and E denotes ebony.
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