Question

Let’s brush up on mapping. For questions 1-8, pure-breeding P0 animals were mated to generate F1 animals heterozygous at the B and W genes. The heterozygous F1 animals were test-crossed and yielded progeny with the phenotypes below. Mutations in the B gene (b) cause a “no bristles” phenotype. Mutations in the W gene (w) cause a “no wings” phenotype. Both genes are haplosufficient. 45% normal bristles, normal wings 45% no bristles, no wings 5% no bristles, normal wings 5% normal bristles, no wings The numbers above suggest that the B and W genes are linked. Part A What is the genotype (correctly written) of the heterozygous F1 animals? Part B In the heterozygous F1 animals, are the alleles in the cis or trans configuration? Part C What were the genotypes (correctly written) of the pure-breeding P0 animals? Part D What is the distance (in m.u.) between the B and W genes? Put a number in the box. Part E In the heterozygous F1 animals, in what percent of the meiosis I tetrads was there a cross-over in the B-W interval (i.e. between the B and W genes)? Put a number in the box. Part F If heterozygous F1 animals had been crossed with each other, what percent of their progeny would you expect to have both recessive traits? You can assume that crossing over can occur in both parents. Put a number in the box.

          Let’s brush up on mapping.  For questions 1-8,
pure-breeding P0 animals were mated to generate F1 animals
heterozygous at the B and W genes.  The heterozygous F1
animals were test-crossed and yielded progeny with the phenotypes
below. Mutations in the B gene (b)  cause a “no bristles”
phenotype.  Mutations in the W gene (w) cause a “no wings”
phenotype. Both genes are haplosufficient.
45%     normal bristles, normal
wings                        
45%     no bristles, no
wings                          
5%       no bristles, normal
wings                               
5%       normal bristles, no
wings                                           
The numbers above suggest that the B and W genes are
linked.  
Part A
What is the genotype (correctly written) of the heterozygous F1
animals?
Part B
In the heterozygous F1 animals, are the alleles in the cis or
trans configuration?
Part C
What were the genotypes (correctly written) of the pure-breeding
P0 animals?
Part D
What is the distance (in m.u.) between the B and W genes? 
Put a number in the box.   
Part E
In the heterozygous F1 animals, in what percent of the meiosis I
tetrads was there a cross-over in the B-W interval (i.e. between
the B and W genes)?  Put a number in the box.
Part F
If heterozygous F1 animals had been crossed with each other,
what percent of their progeny would you expect to have
both recessive traits?  You can assume that crossing over
can occur in both parents.  Put a number in the box.

Added by David S.

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