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It depends on the regions of sequence homology between the two chromosomes. Crossing over occurs through pairing of homologous regions. If there's a substantial stretch of chromosome without a matching homologous region on its pair, that non-homologous region should loop out and not be involved in crossing over. Crossovers will occur only in paired ...


6

In humans and mice anyway ,a lot of it boils down to the recognition of a specific sequence that marks recombination hotspots by PRDM9. http://www.sciencemag.org/content/327/5967/836 Edit - I'm expanding in response to the comment below... Meiotic recombination occurs at vastly greater frequencies in some locations in the genome than others and these are ...


5

The question is very broad and complicated, since the situation may differ in prokaryotes and eukaryotes. Nevertheless, I'm citing a good paper that is closely related to your question: Studies in yeast show that initiation of recombination, which occurs by the formation of DNA double-strand breaks, determines the distribution of gene conversion and ...


3

Why does inversion happen? What is its purpose? Like many other mutations, inversion is generally a neutral mutation. Many inversions, especially those which are between small, intergenic regions, evolve neutrally by drift alone. However, selection can, and does, occur when: inverions create structural problems with meiosis, like pericentric inversions ...


2

The question is unclear to me but hopefully that will help a little bit. My understanding is homologous chromosome pair, which means male and female chromosome There is no male and female chromosome. Chromosomes have no sex. In humans, to the exception of chromosome Y all chromosome can be found in individuals of any sex. There are paternally inherited ...


2

I'm not sure if this is what you're asking for, but in the following image, allele K (or k) is linked to B while A (or a) and B are independent. Again, this is just a guess because your question seems a bit unclear to me.


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I'll bifurcate the question and answer each part one at a time. Germ layer formation: Gastrulation is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar ("three-layered") structure known as the gastrula. These three germ layers are known as the ectoderm, mesoderm, and ...


2

As a silly example: Let's say that you are traveling along a road where you know there are bandits and thieves. You want to finish your journey quickly, and spend very little time on the road, because the more time you spend on the road, the more likely it is that you are robbed and they take your money away. If there are more thieves around one day, you ...


2

There can be and often is more than one crossover per chromosome in meiosis, but how many crossovers occur can depend on the species, sex, age, environment, and which particular chromosome is involved1,2,3. For example, humans typically show 2-3 crossovers per chromosome, but females often show higher recombination rates than males. However, the structure ...


1

Here's a hint: you're right about 0.01 being the recombinant (crossed-over) double homozygous recessive offspring. I think you're forgetting that each offspring contains 2 gamete haplotypes, and so predicting the percent of offspring with a given genotype involves multiplying the frequencies of the individual gametes that produce that offspring. To calculate ...


1

There are two main question: (a) dependence of the frequency of recombination with the distance that separates genes and (b) do all crossover events take place with a single break on one chromosome? Let's give some context. In gametogenesis, chromosome crossover takes place in every tetrad in prophase I. Tetrads are constituted by a pair of homologous ...


1

That's quite an interesting question. Crossing over occur during meiosis, there can be more than one in a chromosome indeed. Let's say two crossing over occurs in the same chromosome (the one with your markers A and B), if they both occured in between your markers, you will see no difference. As you said your markers are far from each other you have a good ...


1

Good thinking. Yes, it is theoretically possible. It is often modelled like this. Have a look at this answer for the maths. Note however, that to my understanding (and I might be wrong) there is typically either 0 or 1 crossover per pair of chromosomes as cross-over is directly related to the way homologous chromosomes bind together during prophase I of the ...


1

Your question and your rephrased question aren't asking the same thing, so you may want to edit your question. Crossover occurs during meiosis, which is a type of cell division that occurs in the generation of gametes, during which of course only the chromosomes from one of the eventual parents would be present. Meiosis doesn't occur in the fetus, except ...


1

Crossing over is believed to be beneficial for evolution. It does not cause only mutations, it allows for the switching and mixing of genetic information. Thanks to crossing over entire protein families evolved, like the hemoglobins. Indeed it is one of the mechanisms that shaped the chromosomes. Some in-silico simulation proved that, in general, adaptation ...


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