8pts the allele b gives rabbits a brown coat mutant and b...

Name: 8pts the allele b gives rabbits a brown coat mutant and b gives black coat wild type phenotype the allele a of a separate gene gives himalayan albimism red eyes white body with pigmented ext 77366
Uploaded: 2023-01-12T21:54:11-08:00
Duration: 5 min 20 s
Channel: Katlin Koehn
Description: 8pts the allele b gives rabbits a brown coat mutant and b gives black coat wild type phenotype the allele a of a separate gene gives himalayan albimism red eyes white body with pigmented ext 77366

(8pts) The allele b gives rabbits a brown coat (mutant), and B gives black coat (wild-type) phenotype. The allele a of a separate gene gives Himalayan albimism - red eyes, white body with pigmented extremities (mutant), and A gives colored pigmentation (wild-type) phenotype. The allele y of a third gene gives yellow fat (mutant), and Y gives white fat (wild-type) phenotype. A female heterozygous for these three genes is test-crossed, and 908 progeny are classified as follows (based on mutant phenotypes; if allele not noted in the phenotype, assume wild-type): 55 wild type; 46 brown, Himalayan, yellow fat; 7 Himalayan, yellow fat; 16 brown; 108 yellow fat; 125 brown, Himalayan; 275 brown, yellow fat; 276 Himalayan MIt a. (1pt) Which are the parental gametes? b. (7pts) Calculate the recombination frequencies between the three loci and draw their proper position on a chromosome.

Transcript

00:01 When we're doing a map genetic question where you want to find the distance between genes, you always want to start by taking that list of phenotypes in the f2 generation and listing them in order from the most common to the least, as you've seen that i've done here.

00:11 So the most common, there was 382 offspring who had the phenotype of dominant b, dominant w, recessive c.

00:18 And so i started there and i worked my way all the way down to the least common, which there was five who were wild type and had all dominant traits for a total of 1 ,000 offspring.

00:30 Now, we do this for a couple reasons.

00:32 Now, the first reason is that we can very easily identify the non -recombinate types, or those offspring who got chromosomes from their parents, and there was no recombination that happened.

00:42 So the parents would either look like this or this.

00:47 And when we identify the non -recombinates, which is just the first two, all the rest of your phenotypes will be recombinants.

00:55 Now, we can identify a lot of different information in the recombinants.

01:01 Which includes identifying the single crossover and double crossover events.

01:07 So you should notice that each, that as we order them from the most comes to the least, we should see that they end up in pairings, inverse pairings, like these two here.

01:18 One of them is dominant b, recessive w, recessive c.

01:21 The other one is the inverse.

01:23 Recessive b, dominant w, dominant c.

01:25 So these two pairings here are an example of a single crossover event.

01:30 The next two, the inverse pairing, is another example of single crossover.

01:34 But the last two that happen the least often are the double crossover events.

01:40 And that's really important because in a double crossover event, we have the middle gene that sort of stays put, but the genes on either side of it get swapped.

01:47 They cross over to the other chromosome.

01:51 And so what ends up happening is that middle gene seems out of place.

01:54 So when we compare the double crossover events to the non -recombinates, we can actually tell which gene is in the middle.

01:59 Middle.

02:01 So i'm going to take the first non -recombinant, which is dominant b, dominant w, recessive c, and i'm going to compare it to a double crossover event, and there should be one that seems out of place, the middle gene.

02:12 So the one i'm going to compare it to is down here.

02:15 Dominant b, dominant w, dominant c.

02:18 So this dominant c is the one that's out of place, and so it's probably our middle, but we'll do the other two just to check.

02:24 The other non -recombinate, recessive b, recessive w, dominant c, double crossover, recessive b, recessive b, reclusive.

02:29 Recessive w, recessive c.

02:32 So again, c is the one that's out of place.

02:34 So c is our middle gene.

02:37 Now that we know that, we can find the distance between the genes...

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