In a diploid species of plant, the genes for plant heigh...

Question

In a diploid species of plant, the genes for plant height and fruit shape are syntenic and separated by 18 m.u. Allele D produces tall plants and is dominant to d for short plants, and allele R produces round fruit and is dominant to r for oval fruit.

Give the same information for a plant with the genotype Dr/dR.

Accepted Answer

Welcome back, everyone. Here's our next question. Recombination is the generation of non parental gene combinations. Whereas linkage is the phenomenon of the physical association of genes on a chromosome in terms of linkage and recombination, which of the following statements is true choice. A recombination frequency is inversely proportional to the distance between the genes present on a chromosome. Choice B strength of linkage is directly proportional to the recombination of genes. Choice C, the lesser the strength of the linkage, the greater the chance of recombination or choice D all of the above. So let's evaluate our answer choices. Keeping in mind that we do have that possibility that all of them could be correct. So with recombination and linkage, let's just think this through you have two genes, we'll call them A and B on A chromosome. If A and B are physically very close together, their linkage is high and their chance of recombination or their recombination frequency is low, there's physically not much distance between them. It's less likely that there will be a crossover event in between them because recombination occurs when the two chromosomes homo of a homologous pair physically cross over with each other. Now, let's look at the scenario where A and B are far apart on a chromosome. In this case, their linkage is low, they have a greater physical distance between them. So they're less likely to be passed along together and therefore a lower degree of linkage and their recombination frequency is higher. There's more physical distance, more likelihood of crossing over, more potential for recombination, a lot of frequency there. So with that in mind, let's evaluate our answer. Choices. Choice A says recombination frequency is inversely proportional to the distance. Well, we saw that when the distance is small, the recombination frequency is low. When the distance is large, the recombination frequency is high. That means they are directly proportional, not inversely proportional. So choice A is not our correct answer. That means we can also eliminate choice D all of the above because we already have one that is not correct. Choice B says strength of linkage is directly proportional to the recombination of genes. Well, again, when we look at what we jotted down here, when the linkage is high, the genes are close together, recombination frequency is low. When the genes are far apart, linkage is low, recombination of frequency is high. So therefore, strength of linkage is inversely proportional to recombination frequency. So that's also not our correct answer. Now, we just have choice C which says the lesser the strength of the linkage, the greater the chance of recombination. And this is correct when we look for the linkage being low. That's in a scenario where the two genes are far apart and our recombination frequency is high. So choice C is the correct statement. So again, in terms of linkage and recombination, which of the following statements is true. Choice C the lesser the strength of linkage, the greater the chance of recombination. See you in the next video.

Key Concepts

Synteny

Genotype and Alleles

Map Units (m.u.)

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