The table given here lists the arrangement of alleles of linked genes in dihybrid organisms, the recombination frequency between the genes, and specific gamete genotypes. Using the information provided, determine the expected frequency of the listed gametes. Assume one map unit equals 1% recombination and, when three genes are involved, interference is zero.

Question

The table given here lists the arrangement of alleles of linked genes in dihybrid organisms, the recombination frequency between the genes, and specific gamete genotypes. Using the information provided, determine the expected frequency of the listed gametes. Assume one map unit equals 1% recombination and, when three genes are involved, interference is zero.

Table displaying dihybrid genotypes, recombination frequencies, and corresponding gamete genotypes for genetic mapping.

Accepted Answer

Hi, everyone. Welcome back. Let's look at our next problem. It says a heterozygous person for two gene pairs. Big, a little A big B little B who is the offspring of big A big A big B, big B and little, a little, a little B little be parents is mated with a double recessive individual little, a little A little B little B individual genotypes and result in numbers of offspring are as follows big. A little A big B little B, 300 big, a little, a little B, little b, 200 little, a little A big B, little b, 150 little, a little, a little B little b 100. Then our question says, what is the recombinant frequency of two gene pairs? Choice a 36.5%. Choice B 46.7%. Choice C 53.3% or choice D 63.5%. Well, let's focus on our end product. We need to calculate the recombinant frequency. So what do we need? What numbers do we need to calculate that from our data given above? So we recall that our recombination frequency formula is recombination frequency equals the number of recombinant offspring divided by the total number of offspring. And then that fraction divided by, I'm sorry, that fraction multiplied by 100% to convert it into a 1%. So we'll need to add up the total number of offspring here and we'll need to find how many of those offspring are recombinant. So now we go up to our information about genotypes. We have a heterozygote parent for both pairs. And what's important to know is which of those, all they inherited from? Which parent. Here's our hero, I guess parent big a little A big B big B and we're told they're the offspring of a double dominant parent and a double recessive parent. So we know that the alley for one parent or all must have been big A and Big B together from one parent and then from the other parent, little A little B must have been inherited together since both parents being homozygous for both traits could only make one type of value. So this heterozygous parents, um we can write out the genotype in a way that helps us see which will be the parental genotypes and which the recombinant. So I will write big A big B draw a line and then little A little B underneath showing the way the all were inherited from the parents. Then I'm going to make a little cross between them to help me visualize the crossovers occurring in the recombinant offspring. Now, important to note, the second parent is a double recessive individual. So that was crossed with little, a little, a little B, little B. So that parent will always make or always give a little, a little B game. It doesn't matter if there's any recombination going on. Those are the only, all that parent has. So it will all be the same. So let's look at the genotypes of our offspring here. First, we'll start with the parental genotypes. So that would be big A big B inherited from the heterozygous parent. And then of course, little A little B and I'm just going to transfer that into the form or the format that the gene type is shown in our data table. So that would be the same as big, a little A big B, little B just to make it easier to match up. Then the second parental genotype will be little a little B inherited from the heterozygous parent course matched with, I'll stop reading that second um set of values because we know it will always be little a little B and written out as in our table. That would be little, a little A little B, little B, those are the parental genotypes. So now I'm going over to my list of offspring numbers and I'm going to label those two genotypes. So the first one With 300 offspring, I'm going to put A P next to it for parental genotype. And the second parental genotype is on the bottom row with 100 offspring that double recessive and I will label that P as well. So now we have our parental genotypes. So we know the other two are recombinant. So I will label those two as recombinant. And we can just double check over here. The first crossover, we double check looking at our heterozygous genotype diagram that I drew out. So a crossover between those two would result in the two recombinant genotypes. One would be big a little B. And what would be a big B and written out in that same format would be big. A little, a little B, little B which are, is in the second row with 200 offspring and then little a little A big B, little B which is in the 3rd row with 150 offspring. So now I have my different genotypes labeled, I need to add up my number of recombinant offspring. So when I look at the two recombinant offspring types, I have 200 and 1 50. So added together that makes 350 recombinant offspring. Now I need the total number of offspring. So if I add together all of the offspring, that would be Plus 200 plus 150 plus my total number of offspring is 750. So now I've got the numbers I need. So I go down to my final formula for recombination frequency and I have the number of recumbent offspring is 350 and I will divide that by my total number of offspring 750, then multiply by 100%. And that will give me 46.7 as my recombination frequency. So now I go over to my answer choices and choice B is 46.7%. So the recombinant frequency of the two gene pairs as those genotypes were given to us with the offspring numbers. This choice B- 46.7%. See you in the next video.

Verified video answer for a similar problem:

Key Concepts

Dihybrid Cross

Recombination Frequency

Interference