The A locus and the D locus are so tightly linked that no recombination is ever observed between them. If Ad/Ad is crossed with aD/aD and the F1 is intercrossed, what phenotypes will be seen in the F2 and in what proportions

F2: 1/4 phenotype Ad (genotype Ad/Ad), 1/2 phenotype AD (genotype Ad/aD): 1/4 phenotype aD (genotype aD/aD)

Explanation:

In this case, A and D loci are strongly linked and there is little or no recombination between them. Therefore, Ad/Ad and aD/aD individuals will produce only one type of gametes (i.e., individuals Ad/Ad only can produce Ad gametes, while aD/aD individuals only can produce aD gametes), thereby all F1 will be Ad/ aD. Finally, Ad/aD individuals can produce two types of gametes: Ad and aD, thereby the F2 will be 1/4 Ad/Ad (phenotype Ad), 1/2 Ad/aD (phenotype AD) and 1/4 aD/aD (phenotype aD)  

Parental cross:   Ad/Ad x aD/aD

F1 generation:  Ad/aD

F2 generation:        

                Ad            aD

Ad         Ad/Ad       Ad/aD

aD         Ad/aD       aD/aD

F2 generation: 1/4 Ad/Ad (phenotype Ad), 1/2 Ad/aD (phenotype AD) and 1/4 aD/aD (phenotype aD)

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.