Three-spined stickleback fish live in lakes formed when the last ...

Question

Three-spined stickleback fish live in lakes formed when the last ice age ended 10,000 to 15,000 years ago. In lakes where the sticklebacks are prey for larger fish, they develop 35 bony plates along their body as armor. In contrast, sticklebacks in lakes where there are no predators develop only a few or no bony plates.

Loss-of-function mutations in the coding region of the homologous gene in humans result in loss of hair, teeth, and sweat glands, as in the toothless men of Sind (India). What does this suggest about hair, teeth, and sweat glands in humans?

Accepted Answer

Welcome back, everyone. Let's look at our next problem. It says in Huntington's disease, the number of C A G repeats generally increases from one generation to the next. Based on this, which of the following statements is most likely true regarding the age of onset of symptoms in a child whose father has C A G repeats on his fourth chromosome and the child has 45 C A G repeats on the same chromosome choice. A, the child is likely to develop symptoms earlier than the father due to the expansion of C A G repeats choice B, the child is likely to develop symptoms later than the father due to the expansion of C A G repeats. C, the father and child are equally likely to develop symptoms at the same age. Due to the expansion of C A G repeats or D. The number of C A G repeats has no correlation with the onset of symptoms in Huntington's disease. Well, we can note that in Huntington's disease, uh which is an autism dominant disorder. So the child needs only needs to inherit the affected all from one parent. And as your question reminds us, it is caused by these C A G repeats that do increase in general from one generation to the next. So each child that inherits the repeats from a parent will have more repeats. And in fact, you can have people inherit uh a small number of repeats that will not cause the disease. So, in general, between 37 to 90 repeats in the gene causes Huntington's disease to develop. And as we can recall, Huntington's disease tends to develop later in life, but the number of repeats does affect this. So we can actually cross out choice. D the number of C G repeats has no correlation with the onset of symptoms in Hunting P's disease. In general. A higher number of repeats will result in a lower age of onset for the disease. So in this case, we'll go ahead and circle choice A which says the child is likely to develop symptoms earlier than the father due to the expansion of C A G repeats. As we expected, we saw a greater number of repeats in the child and this does lead to a higher risk of developing symptoms at an earlier age of onset. See you in the next video.

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