1. what phenotypes/genotypes would be observed in the f2 generation if no crossovers occurred? 2. why is a test cross usually used in preference to production of an f2 generation to measure linkage? 3.why were the earliest studies of linkage were done with genes on the x-chromosome?

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.

a bird that nests only in a particular tree species.