Question

Given the following illustration, what is the correct gene order? NCO DCO prwd+ ct prt wd ct* prt wd ct pr wdt ct O prwd ct Oct prwd O pr ct wd

Answer 1

Answer to the first question:

To determine the gene order from NCO (non-cross overs) and DCO (double cross overs) we need to check which gene changed its position to convert an NCO to DCO.

Given, in NCO, the genotype is :

pr wd+ ct+ / pr+ wd ct,

and genotype of DCO is pr+wdct+/prwd+ct, which can be written as :

pr wd+ ct / pr+ wd ct+

Note that the gene "ct" has moved to create DCO from NCO . In both NCO and DCO 'pr wd+' and 'pr+ wd' appear together, whereas gene ct is present with pr+ wd in NCO but with pr wd+ in DCO. Similarly, ct+ gene is with pr wd+ in NCO, but with pr+ wd in DCO. Thus, gene ct should be in the middle.

Hence, the correct choice should be:

(c) pr ct wd

IUTIVE NCO DCO prwd' ct prt wd ct* prt wd ct prwdt ct O prwd ct ct prwd O prct wd