In rabbits, chocolate-colored fur (w⁺) is dominant to wh...

Question

In rabbits, chocolate-colored fur (w⁺) is dominant to white fur (w), straight fur (c⁺) is dominant to curly fur (c), and long ear (s⁺) is dominant to short ear (s). The cross of a trihybrid rabbit with straight, chocolate-colored fur and long ears to a rabbit that has white, curly fur and short ears produces the following results:

Phenotype Number
White, short, straight 13
Chocolate, long, straight 165
Chocolate, long, curly 13
White, long, straight 82
Chocolate, short, straight 436
Chocolate, short, curly 79
White, short, curly 162
White, long, curly 450
1400

Determine the interference value for this cross.

Accepted Answer

Hi, everybody. Let's take a look at our next problem. It says in a tri hybrid cross, when one crossover decreases or influences the probability of other crossovers nearby, it implies the occurrence of choice a concordance B interference C mutation or D evolution. When we see that one crossover occurring decreases the likelihood or interferes with another crossover occurring. That phenomenon is choice B interference. And we can actually measure to what degree that interference takes place using something called the coefficient of coincidence to give a mathematical measure of that. And that is calculated by dividing the observed number of double crossovers seen in the offspring divided by the expected number of double crossovers. Let's look at our other answer choices to understand why they are not correct. Well, we're talking specifically about one crossover interfering with the possibility of another. So we can go ahead and eliminate choice D evolution. As we know evolution just refers to the change in a species over time in response to outside pressures. And then also choice C is pretty easy to eliminate mutation just referring to any change to the DNA sequence. Finally, concordance might be a little tricky one we're not as familiar with. In genetics. Concordance refers to this situation where in a pair of organisms, the likelihood of both of the pair having a specific phenotype if one of the pair has the trait. So you commonly see this concept in twin studies where you say something like if one of a pair of twins has autism, what is the probability that the other twin has autism as well or something with siblings or cousins or something like that? So that's the concept of concordant, but it's not what we're looking for. So that's why that's not our answer choice. So again, in a try hybrid cross, when one crossover decreases or influences the probability of other crossovers nearby, that implies the occurrence of choice B interference. See you in the next video.

Key Concepts

Dominance in Genetics

Trihybrid Cross

Genetic Interference

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