Define the following: (a) polygenic, (b) additive alleles, (c) correlation, (d) monozygotic and dizygotic twins, (e) heritability, (f) QTL, and (g) continuous variation.

Video transcript

Everybody. Let's take a look at this practice problem. Together the blank twins are derived from a single zygote. While the blank twins came from two separate fertilization events, recall that the zygote is the result of the union of a female and male gammy. So here we have a male gammy and a female gammy forming a zygote that has a complete set of D. N. A. Now twin development can occur in one of two ways. So let's review that The first way is depicted here. And so in this type of development you have the male gammy and the female gammy coming together to form a single zygote. Then this zygote splits into two. So you get two genetically identical zygotes, they have the same D. N. A. This type of development. The twins are called identical or mono psychotic, and mono means one. So mono references that they came from one zygote. Now the second way twins can develop is in this example you have to separate fertilization events where a male gammy and female gammy combined to form a zygote because you have to separate male gametes and two separate female gametes. The two zygotes that are produced are not identical. They have different D. N. A. This type of twin development. The twins are called fraternal or dies exotic. Di means two. So di references that they came from two separate zygotes. So our first part of our question is blank twins are derived from a single zygote. So the first fill in the blank will be either identical or mono psychotic meaning we can eliminate both B. And C, and the second term will be fraternal or die psychotic. And so the correct answer is D. The identical twins are derived from a single zygote, while the fraternal twins came from two separate fertilization events. Alright, everyone. I hope you found this helpful, and I'll see you soon for the next practice problem.