In reptiles, sex determination was thought to be controlled by se...

Question

In reptiles, sex determination was thought to be controlled by sex-chromosome systems or by temperature-dependent sex determination without an inherited component to sex. But as we discussed in section 7.6, in the Australian lizard, Pogona vitticeps, it was recently revealed that sex is determined by both chromosome composition and by the temperature at which eggs are incubated. What effects might climate change have on temperature-dependent sex determination in this species, and how might this impact the sex ratio for this species in subsequent generations?

Accepted Answer

Hello, everyone here's our next question. It says the treats controlled by recessive genes that are linked with the X. Chromosome only are called X linked recessive traits and such genes are called X linked recessive genes. What is true about X linked recessive traits? So let's notice as we look at our answer choices, the choice D. Is all of the above. So we have that option. Let's look at choice A. It says they are more common in males than females. Well this is true of excellent recessive traits. Males only have a single X chromosome so they only need to inherit one of these recessive alleles to show the trait. So even though it's recessive, because they have no second X chromosome that could mask that expression with a dominant allele, they only need one to inherit one allele. And therefore these traits appear much more often in males than females. Since females have to inherit two copies. So it happens much less frequently in females. Let's look at choice B. They show a zigzag pattern of inheritance. Well this is correct because they cannot be passed directly from father to son. A father passes a Y chromosome not an X. Chromosome to his son so a father cannot transmit the trait directly to his son. Instead. You see this sort of zig zag from a grandfather who was affected, we'll say we'll call the straight little A. Because he carries that recessive value on his single X chromosome. He passes that down to all of his daughters. Will say to a daughter who is not affected unless she's inherited for some reason, another away from her mother but a carrier while her father is affected. Then she passes half of the time that a little onto her son. Or we'll say grandson who again only has a single X. Chromosome. And so now is affected despite only having that single recessive value. So you see this zigzag pattern rather than direct inheritance. And then finally, males are always Hamid, I guess for X linked recessive genes. And this is correct. Males have only a single X chromosome, so they only carry one allele of the recessive trait. Since all our answers are correct here. So our answer is choice D All of the above are true about excellent recessive traits. See you in the next video.

Key Concepts

Temperature-Dependent Sex Determination (TSD)

Sex Chromosome Systems

Impact of Climate Change on Sex Ratios

Watch next