In Drosophila, singed bristles (sn) and cut wings (ct) are both caused by recessive, X-linked alleles. The wild type alleles (sn+ and ct+) are responsible for straight bristles and intact wings, respectively. A female homozygous for sn and ct+ is crossed to a sn+ct male. The F1 flies are testcrossed. What is the map distance between sn and ct? The F2 males are distributed as follows

sn ct

13

sn ct+

36

sn+ ct

39

sn+ ct+

12

25 mu

Explanation:

When two genes are linked, they show the tendency to get inherited together. Thus, the resulting progeny has more parental combinations than the recombinant ones. Here, snct and sn+ct+ are in lowest numbers hence they are the recombinants.

Map distance between two genes = recombination percentage = ( Number of recombinants / Total progeny ) * 100

= [( 13 + 12) / ( 13 + 12 + 36 + 39 )] * 100

= ( 25 / 100 ) * 100

= 0.25 * 100 = 25%

Since there is 25% recombination, map distance between sn and ct genes is 25 mu or 25 Cm.

the correct answer is - ability to find a mate

sulfur dioxide

explanation: acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. these substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.