1. Work with the provided parental stocks to determine a,b and c: . Homozygous n
ID: 273495 • Letter: 1
Question
1. Work with the provided parental stocks to determine a,b and c:
. Homozygous normal (wild-type) strain and
. A strain carrying three homozygous mutant markers: cross-veinless wings, forked bristles and yellow body.
A: Indicate whether to cross (i) mutant females with wild-type males, or (ii) mutant males with wild-type females, or (iii) both , to produce F1 generation that will enable you to determine if the traits are dominant or recessive, and if they are sex-linked.
B: Indicate whether the three mutant genes are: (i) recessive or dominant and, (ii) carried on the autosomes or sex-linked?
C: Determine whether the mutant genes are independent or linked, using a testcross. Knowing which are the recessive genes, indicate which individuals you would mate in this testcross. (Draw a mating diagram & use the forked line method )
Explanation / Answer
A) To know, if the markers are recessive or dominant. We can cross homozygous mutant females to homozygous wild type males or we can cross homozygous mutant males with homozygous wild type females. The F1 generation will be heterozygous for the markers. If the F1 generation develop mutant phenotype than the mutation is dominant. And if the F1 generation is normal, then the mutant markers are recessive. This is because, if the mutant phenotype is dominant one allele is sufficient to express the phenotype however if the mutant phenotype is recessive both recessive alleles are required to express the mutant phenotype.
To determine if they are sex linked, both crosses need to performed and the ration of females and males expressing the mutant genotype need to be analysed.
B) i) Same as for A.
ii) The F1 generation will be heterozygous for the markers for males and females and the distribution will be equal i.e 1:1 ration in males:females if it is carried by autosomes.
If it is carried by sex linked genes, the distribution ration between males and females will be different.
C) You need to the know if the genes are recessive or dominant to answer this question.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.