Clouded sulfur butterflies are common in our area and can be

Clouded sulfur butterflies are common in our area and can be either yellow or white While most individuals in the total population are yellow, it is known that a single autosomal gene controls color and that the white allele is completely dominant over the yellow allele. However, when analyzing crosses we find the following results: Yellow male x yellow female = 100% yellow males: 100% yellow females Yellow male x yellow female = 100% yellow males:50% white females:50% yellow females Yellow male x white female = 100% yellow males:100% white females Yellow male x yellow female = 100% yellow males:100% white females yellow females Yellow male x white female = 100% yellow males:75% white females: 25% this trait in clouded What do these results suggest about the genetic inheritance patterns of sulfur butterflies? In cats, curled ears result from a allele (CU) that is dominant over an allele (cu) for normal ears.

Solution

First of all, the gene for color is not autosomal, but is X-linked. The results suggest this. This I am saying because the results of male and female progeny are different.

Suppose the gene for white color is W, and that for yellow color is Y. \"Y\" is epistatic over \"W\". \"yw\" will show the recessive yellow phenotype. White will show its color only when \'yy\' genotype is there.

The crosses are:

1. Yw yellow male X YYww yellow female = All yellow progeny

2. yw (yellow male) X YyWw yellow female = \"Yw\" and \"yw\" yellow males, and white: yellow females in 1:1 ratio

3. Yw (yellow male) X yyW_ (white female) = Now, in this cross, white males should be there. But your cross is saying that the results are yellow males. So, this is not possible.

This further suggests that the cross is autosomal. In autosomal cross also, all results given are not possible.

I come to the inference that the color of butterflies is not genetic; infact it is environmental.

Please note that the effect can be genetic only if it is a polygenic trait. Multiple genetic loci determine this color trait. The butterfly having more dominant alleles will give white color and that having less dominant alleles will give yellow color. This can be possible only if intensity of yellow color is differing in different crosses. These results are not there, so, I cannot come to the final inference that it is polygenic.