Imagine that you are a breeder of Labrador retriever dogs....

Name: Problem 18, Chapter 12: Biology: The Dynamic Science
Uploaded: 2021-12-11T03:21:47-08:00
Duration: 5 min 31 s
Channel: Miwa Wenzel
Description: Imagine that you are a breeder of Labrador retriever dogs. Labs can be black, chocolate brown, or yellow. Suppose that a yellow Lab is donated to you and you need to know its genotype. You have a range of dogs with known genotypes. What cross would you make to determine the genotype of the donated dog? Explain how the resulting puppies show you the Lab's genotype.

Imagine that you are a breeder of Labrador retriever dogs. Labs can be black, chocolate brown, or yellow. Suppose that a yellow Lab is donated to you and you need to know its genotype. You have a range of dogs with known genotypes. What cross would you make to determine the genotype of the donated dog? Explain how the resulting puppies show you the Lab's genotype.

Key Concepts

Epistasis

Epistasis is the interaction between different genes, where the expression of one gene masks or modifies the expression of another gene. In many inheritance systems, this is particularly important when one gene’s recessive phenotype overrides the other gene’s alleles, thereby influencing the final expressed trait.

Punnett Square

A Punnett square is a visual tool that is used to predict the possible genotypes and phenotypes of offspring resulting from a cross between individuals. By organizing the alleles from each parent into a grid, it enables the calculation of expected ratios and the assessment of carrier status or mutation presence.

Test Cross

A test cross is a genetic mating where an individual with an unknown genotype is crossed with an individual that is homozygous recessive for the trait. This strategy allows the determination of whether the unknown genotype is homozygous dominant or heterozygous based on the distribution of phenotypes among the offspring.

Mendelian Inheritance

Mendelian inheritance involves the transmission of traits according to predictable ratios based on dominant and recessive alleles. This concept is foundational to genetics and helps in understanding how each parent contributes one allele to their offspring, which can then be analyzed to determine underlying genotypes.

Transcript

00:01 All right.

00:02 Hi.

00:03 So today we have a question about labrador retrievers, and labs are famous in genetics for use as an example of epistasis, which means that we have the interaction of genes.

00:18 So what we have here for labrador's are two genes, a capital b, which is the dominant form of one gene.

00:27 And this gene is the gene that controls color.

00:32 So we're going to say color, which is black or going to be or brown or chocolate, we could say.

00:41 Chocolate.

00:44 And the other gene of interest is going to be our e gene, which i'll draw here as a capital e at the moment.

00:51 And this is going to tell us if we see the black or brown or chocolate, i should say again.

01:07 You want to stick with our lab colors.

01:10 Chocolate.

01:13 Okay.

01:15 And so for each of these, we're going to have the dominant or recessive form.

01:19 So for our b gene, we're going to have black as our capital b here.

01:26 And chocolate is going to be the lowercase b.

01:31 And then for our e gene, we're going to have seeing the color is going to be our capital e.

01:40 And then we can say like not seeing the color or perhaps better is to say if we mask the color.

01:49 We can say we mask the color.

01:53 This is going to be our little e, our recessive gene.

01:58 Okay.

02:01 So in this way, we can realize that anything that has a little e, little e, is this is how we get our yellow lab color, because we're masking the black or the chocolate.

02:12 This is the epistasis part.

02:13 We're interacting genes.

02:15 So we mask the black or the chocolate, and we just get yellow.

02:20 And the only way we can see the black or the chocolate is we have a big e.

02:26 So it could either be capital e little e, or it could be capital e, capital e...

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