Question

A) This setup involves an F1 in which the fully heterozygous female has the genes y and w coupled and ct not coupled. The arrangement for the cross is therefore: y w +/+ + ct x y w +/Y. It is important at this point to determine the gene sequence. Using method I or II, examine the parental classes and compare the arrangement with the double crossover (least frequent) classes. Notice that the w gene "switches places" between the two groups (parentals and double crossovers). The gene that switches places is in the middle. Therefore, the arrangement as written above is correct.

b) y → w = (9 + 6 + 0 + 0)/1000 x 100 = 1.5 map units
w → ct = (90 + 95 + 0 + 0)/1000 x 100 = 18.5 map units
y –––w –––––––––––ct
0.0 1.5 20.0

c) There were .185 x .015 x 1000 = 2.775 double crossovers expected.

d) Because the cross to the F1 males included the normal (wild-type) gene for cut wings, it would not be possible to unequivocally determine the genotypes from the F2 phenotypes for all classes.

Answer 1

The question relates to a genetic cross involving genes y, w, and ct. The distances between the genes and the expected number of double crossovers can be calculated. The genotypes of the F2 cannot be determined based on phenotypes alone.

Step-by-step explanation:

Based on the information provided, the question relates to a genetic cross involving the genes y, w, and ct. The arrangement of the cross is determined by the presence or absence of couplings between these genes. The gene that switches places between the parental and double crossover groups is in the middle, confirming the arrangement as written.

The distances between the genes can be calculated using the recombination frequencies. The distance between y and w is found to be 1.5 map units, and the distance between w and ct is found to be 18.5 map units.

The number of double crossovers expected can be determined by multiplying the recombination frequencies of the three gene pairs. In this case, there are expected to be 2.775 double crossovers.

Lastly, because the F1 males in the cross have the wild-type gene for cut wings, it is not possible to determine the genotypes of the F2 based solely on their phenotypes.