In Drosophila, the genes for eye color, wing shape, and wing length are located on chromosome II. Purple eyes (pr), arc bent wings (a), and vestigial wings (vg) are the mutant forms of the wild type traits red eyes, straight wings, and long wings, respectively. You've discovered some data in your genetics laboratory which indicates that the distance between vg and pr is 12.5 m. u., the distance between a and pr is 44.7 m. u., and the distance between a and vg is 32.2 m. u. what is the chance of a double crossover between these three genes

The expected double recombinant frequency = 0.0402 = 4.02%

Explanation:

Available data:

→ Two genes that are very close will have a few recombination events and are strongly bounded.

→ The map unit is the distance between the pair of genes for which every 100 meiotic products, one of them results in a recombinant one.

1) First, we need to know their order in the chromosome, and to do so, we need to compare the distances between them.

The most distant pair is a-pr

apr---

    ║44,7 MU║

From  gene a to vg there are 32.2 MU

avgpr---

    ║44,7 MU║

    ║32.2 MU║

Finally, de distance from vg to pr is 12.5 MU

avgpr---

    ║44,7 MU║

    ║32.2 MU║--12.5 MU--║

We can name region I to the distance between a-vg, and region II to the distance between vg-pr.

2) To calculate the recombination frequency, we have to know that 1% of recombinations = 1 map unit = 1cM. And that the maximum recombination frequency is always 50%.

1 MU 1% of recombination

32.2 MU X =  32.2 % of recombination

12.5 MUX =  12.5 % of recombination

3) The expected double recombinant frequency = recombination frequency in region I x recombination frequency in region II.

The expected d. recombinant frequency = 32.2%  x  12.5% = 0.322 x 0.125

The expected double recombinant frequency = 0.0402 = 4.02%

answer; i believe that the correct answer is (lung);

tsd is temerature dependent sex determination.

tsd: it is a type of environmental sex determination in which the temperature experienced during embryonic/ larval development (ambient temperature for development) determine the sex of the offspring.

crocodile displays the tsd where the ambient temperature of the developing egg determines the individual's sex. for example in the american alligator's eggs, incubation at 33 ºc produces mostly males, while incubation at 30 ºc produces mostly females. so if the american alligator's egg will get the ambient temperature (33 degree celcius)during embryonic development from egg, the offspring will be male and same for the female sex determination.