Contrast penetrance and expressivity as the terms relate to pheno...

Question

Contrast penetrance and expressivity as the terms relate to phenotypic expression.

Accepted Answer

everyone. Let's look at our next question. It says blank is the proportion of animals with a certain genotype that exhibit the phenotype linked to that genotype? Whereas the expression level of a given phenotype as a phenotype inside an individual is referred to as blank. And our answer choices give us three different terms. Expressivity penetrates and recombination frequency. Well let's kind of look through at the definition of each of these things. Recall that from our content video and then try and match them correctly. So the first one here that we see in choice A is expressivity. Well expressivity is the strength of a fanatic trait in a given individual who has the genotype for that phenotype. So we're used to thinking like um you know this pea plant has the gene for a yellow pea. All the peas with that genotype um will have be yellow but that's not always the case. So sometimes you might have the genotype that usually would lead to a specific phenotype but it's you know not express expressed to only a lesser degree not expressed at all. So the strength of a fanatic trait in a given individual. So this is key for this one here. Um expressivity refers to a single individual and what's going on with their expression of a given gene. So that's as opposed to penetrates And penetrations is the proportion of individuals in a population with a certain genotype who expressed the given phenotype. So with penetrates we're talking about a whole population with a certain genotype? Not just a single individual? As saying in this group of people that have the same exact genotype, what percent of them expressed? That phenotype? It might be less than 100 one way to keep these two straight because it can be a little confusing. Is if we think penetrates think of this letter P. Here, penetrations equals population. So penetrates population and expressivity. You might think of the phrase express yourself. Expressivity talks about an individual. And if you tell someone to express themselves, you mean to be an individual be unique so that it can be just a little tip to help you keep those two straight. Finally we have the word recombination frequency here and recombination frequency is as you might guess from the word, the frequency of chromosomal crossover between two genes. So you've got two genes on imagine a little arm of the chromosome. How often do the two chromosomes crossover during mitosis and cause those genes to be switched between the chromosomes of two different parents. It's used in mapping gene locations on a chromosome because the closer the genes are together the more frequently they'll cross over. But it's not related to our question about expressions of phenotype with the given genotype. So we can eliminate C. And D. Since recombination frequency is not going to describe what we're looking for. So let's go back to our question which says blank is the proportion of animals with a certain genotype that exhibit the phenotype. So they were talking about a group of animals, A population. So that's our word penetrates penetrates population. So when we look at our answer choices, we see that choice B. Has penetrates first and then expressivity will double check the second blank says the expression level the given genotype as phenotype. Inside an individual is referred to as blank. Again we think about individual, we think about expressivity. So our answer is going to be choice B penetrates for the first word, expressivity for the second. And we're gonna go and eliminate choice A. Which has the two correct terms but in the wrong order. So again that's how we keep that straight. We talk about a proportion from population. We're talking about penetrates. When we're talking about inside an individual. How genes expressed. We talk about expressivity and we can actually have a little handy visual guide to understand the difference here. I'll put up this little sort of um simple little diagram over there shrink that down so we can get this back in the picture. And we would say that this row here shows variable expressivity. Every person, every person in this row expresses the trait that they have the genotype for. But to different degrees. As shown by the different shades here down in this row here this shows variable penetrates because we're going to imagine all these peoples all these circles represent individuals with a given genotype. But here you've got two people that don't express it at all even though they have the gene for the trait, they also show variable expressivity since the two people that express it express it to a different degree. But that's just a little visual guide to help understand that difference between expressivity and penetrates. But again, looking back at our problem, um, Choice B penetrates is the proportion of animals with a certain genotype that exhibit the phenotype. While the expression level of a given genotype as phenotype inside an individual is expressivity. See you in the next video.

Contrast penetrance and expressivity as the terms relate to phenotypic expression.

Key Concepts

Penetrance

Expressivity

Phenotypic Variation

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