The table below shows the genotype frequencies and allele frequencies for two populations, population 1 and 2. Now in one of these populations, there's been random mating, and in the other population, there has been inbreeding. We need to identify in which population you think random mating has occurred and in which population there has been inbreeding, then answer the question below. Alright. So let's take a look at the table.
We have two populations with 1000 individuals, population 1 and population 2. We see the three different genotypes here, and we have the different counts. You can see that they have very different numbers there, and then we also see the allele frequencies. And we see that these two populations have the same allele frequencies. Both of them are p and q both equal 0.5.
Alright. So just take a second. Look at that. Think about what you would expect under inbreeding and under random mating, and see if you can figure this out. Alright.
I'm going to do some calculations in a second just to prove it to myself. But remember, under inbreeding, we said you get excess homozygosity. You get more homozygotes in the population than you would otherwise expect. So population 2, well, it has a lot more homozygotes. So I think population 2 has inbreeding.
Now I can sort of figure out what my Hardy-Weinberg expectation would be just by doing p2, 2pq, and q2 for my three genotypes here. So p2, well, 0.5×0.5, that's 0.25. 2pq, that's going to equal 0.5, if you do the math. And q2, well, it's also 0.5×0.5, that also equals 0.25. And you get the actual counts, well, there's 1000 individuals.
I'd multiply that by 1000, and you can see that matches population 1 perfectly. So population 1 is in Hardy Weinberg equilibrium. Population 2 is way out because there are way too many homozygotes. So now I feel really good about saying that the population with random mating is population 1, because it is in Hardy Weinberg equilibrium.
The population with inbreeding, I say population 2, because it has way more homozygotes than I would otherwise expect. Alright. Now we have to answer c here, and I'm going to scroll down, so that we can see this a little bit better. And c says well, it's a little bit of a word salad. We got to straighten it out.
It says fill in the sentence below using the words allele and genotype. Both words will be used twice. Alright. What it says here is for an actual population, knowing the blank frequency will tell you the blank frequency. But knowing the blank frequency does not tell you the blank frequency.
Alright. And we've got to put allele and genotype on those lines to make it make sense. Now this kind of makes me want to cry a little bit. That feels really confusing, but let's break this down. Let's just look at the first half of it first.
For an actual population, knowing the genotype frequency will tell you the allele frequency. Alright. When we got an actual population, which thing did we sort of get to count, and which thing did we have to calculate? Well, when we had an actual population, we were given the genotype frequency. And from that, we could calculate the allele frequency.
Right? We would calculate the allele frequency from the genotype frequency for an actual population. But then it says, but knowing the allele frequency does not tell you the genotype frequency. Right? If I know the allele frequency, I can't predict the genotype frequency for an actual population.
Right? You can see here in our table, well, we have identical allele frequencies, but we cannot calculate the genotype frequencies. Now we could go the other way. We didn't do all that math out. We could go the other way, though, and figure out that both of those have allele frequencies of 0.5.
So here I am going to say that knowing the allele frequency does not tell you the genotype frequency. Now you may be saying, wait a second, we spent a lot of time calculating genotype frequency from allele frequency. Yes. But that was when we assumed the population was in Hardy Weinberg equilibrium. Here, this is an actual population.
We cannot make that assumption for actual populations. Alright. With that, we figured it out. We got more practice to come. Check it out.
It'll be fun. At least, I think it will be.