A species of cereal rye (Secale cereale) has a chromosome number ...

Question

A species of cereal rye (Secale cereale) has a chromosome number of 14, while a species of Canadian wild rye (Elymus canadensis) has a chromosome number of 28. Sterile hybrids can be produced by crossing Secale with Elymus.

Given that none of the chromosomes pair at meiosis I in the sterile hybrid (Hang and Franckowlak, 1984), speculate on the anaphase I separation patterns of these chromosomes.

Accepted Answer

Hi everyone. Let's look at our next question. It says why are hybrids such as mules not capable of producing viable gametes. Well let's recall that hybrids are the offspring of parents of two different species and as a result they have two different types of chromosomes. The chromosomes they inherit from their two parents are slightly different. So it can mean just that those chromosomes aren't quite uh similar enough that causes them problems in pairing up as homologous pairs, but they may actually have different numbers of chromosomes. Um That's actually the case with mules. Um You'll of course we'll put this up here And we put up just a little uh chart here. The mule is the offspring of horse and donkey but a horse has 64 chromosomes while donkey only has 62 chromosomes. So this mule will have only 32 chromosome have 32 chromosomes for its horse parent and only 31 chromosome from its donkey parent. This means when the homologous pairs line up um for preparatory to crossing over um and then getting ready for meta phase. During my aosis, they will not be able to match up properly because you're gonna have one extra chromosome that has no pair. And that's going to stop this from happening since the cell can tell that things are not lined up properly. So with that in mind, let's evaluate our answer choices choice A says because mitosis is hindered. Well this is not correct, mitosis has no problem. The mule is perfectly healthy and its own cells can grow and divide because the mitosis, You're just pulling apart sister chroma tides. You don't need homologous pairs to line up, Choice B says, because they lack the necessary proteins. That's not correct. They have all the proteins they need for this to go forward. Just mismatched chromosomes, Choice C says, because they usually have genetic disorders. Well, this is not correct, mules can be perfectly healthy. Um They just have different genes. They don't have genetic disorders any more so than any other animal. And finally, Choice D. Because mitosis is disrupted and this is the reason um with one chromosome left UNP aired sends a message to the cell that something is going wrong and chaos is halted and the mule cannot produce gametes which are the end product of mitosis. So what why are hybrids such as mules not capable of producing viable gametes? Choice D. Because mitosis is disrupted in the next video.

My Courses

Chemistry

Biology

Math

Physics

Business

Social Sciences

Programming

Product & Marketing