Tuesday, July 14, 2009

Bio- 2 questions. Help please thanks!!!?

A certain species of grasshopper can have red stripes, yellow stripes, or red and yellow stripes. An RR grasshopper has red stripes, an rr grasshopper has yellow stripes, and an Rr grasshopper has red and yellow stripes.





1.Which type of inheritance is this an example of?


A. codominance


B. sex-linked inheritance


C. recessive inheritance


D. incomplete dominance





A grasshopper with red stripes mates with a grasshopper with yellow stripes. What ratio would you expect to see in the phenotypes of their offspring?


A. 1 with red stripes: 2 with red and yellow stripes: 1 with yellow stripes


B. all with yellow and red stripes


C. 2 with red stripes: 2 with yellow stripes


D. all with red stripes





Thanks everyone. I just do not get this and need some help. well thanks!

Bio- 2 questions. Help please thanks!!!?
1.Which type of inheritance is this an example of?


A. codominance





Co- means with, so this is when two alleles can be expressed simultaneously, ie. with each other. This is the same situation as with blood type (AB from one A allele and one B allele).





Incomplete dominance is when there is a blending of alleles, as with pink flowers when a white and a red allele are present.





A grasshopper with red stripes mates with a grasshopper with yellow stripes. What ratio would you expect to see in the phenotypes of their offspring?





Use a Punnett square to figure this out: RR on one axis and rr on the other. This means that each possible offspring will be Rr, which means all grasshopper offspring have red and yellow stripes (100% heterozygous)
Reply:1.a


2.a
Reply:1. When both phenotypes are expressed, that's considered Co-dominance. Neither trait is dominant over the other, so both are able to be expressed phenotypically.





2. A red stripe (RR) and yellow stripe (rr) cross would be RR X rr, and with both parents only donating one allele, the possible combinations would all be Rr, or red and yellow stripes phenotype. Each parent can only donate one allele, since they are both homozygous. So, the offspring will all be heterozygous with Rr, or all yellow and red stripes.


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