33. In the European dog flea (an XX:XO species) there are two traits under inves

Question

33. In the European dog flea (an XX:XO species) there are two traits under investigation. The first trait determines the length of the bristles on the body and is generally symbolized by the letter (s). The second trait involves the number of claws at the tip of each leg and is generally symbolized using the letter (r). The bristles and terminal claws are very important in helping the flea to latch onto a host animal. Bristle types are simply long and short and claws can be single or paired. A single clawed, short bristle female was crossed to a long bristled male with paired claws. All of the F1s had a single claw and long bristles. The F1s were allowed to mate brother to sister to produce the F2s listed below:

Males:

39 long bristles, single claw

37 long bristles, paired claws
13 short bristles, single claw
12 short bristles, paired claws

 females:    78 long bristles, singleclaw   26 short bristles, single claw

a)Which general type of chromosome does each trait reside on?

Bristle length gene _______________ claw number gene _______________

What are the genotypes of the two P1 individuals that were crossed?

Explanation / Answer

it follows mendelian's laws of inheritance
in F1 generation , all progeny showed dominant phenotype
in F2 generation , there are 4 phenotypes
in the ratio 9:3:3:1
so , bristle length gene chromosome is Ss

claw number gene chromosome is Rr

genotype of two P1 individuals are Ss ; Rr and Ss ; Rr

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