The exchange occurs in segments over a small region of homology similarity in sequence, ie. The new combinations of DNA created during crossover provide a significant source of genetic variation. Crossing over is a phenomenon that happens during Meiosis I in the attempt to create genetic diversity. Crossing over typically occurs between which of the following structures?
Crossing over occurs when chromosomal homologs exchange information during metaphase of Meiosis I. During this stage, homologous chromosomes line up on the metaphase plate and exchange genetic information. Crossing over occurs during prophase I when parts of the homologous chromosomes overlap and switch their genes.
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Correct answer: Prophase I. Explanation : During prophase I homologous chromosomes will line up with one another, forming tetrads.
Report an Error. What is the evolutionary purpose of cells that undergo crossing over? Possible Answers: To produce gametes that are genetically identical. Correct answer: To increase genetic diversity.
Explanation : Crossing over is a process that happens between homologous chromosomes in order to increase genetic diversity. Example Question 3 : Understanding Crossing Over. During which step of cell division does crossing over occur?
Genes that are located farther apart on the same chromosome have a greater likelihood of undergoing recombination, which means they have a greater recombination frequency.
Recombination in meiosis. Further Exploration Concept Links for further exploration meiosis DNA chromosome gene linkage principle of independent assortment eukaryote nucleus gamete haploid recombination frequency Principles of Inheritance.
Related Concepts In meiosis, they're lined up on the meiotic plates, [as they're] sometimes called, and those paired chromosomes then have to have some biological mechanism that sort of keeps them together. And it turns out that there are these things called chiasmata, which are actually where strands of the duplicated homologous chromosomes break and recombine with the same strand of the other homolog.
So if you have two Chromosome 1s lined up, one strand of one Chromosome 1 will break and it will reanneal with a similar breakage on the other Chromosome 1. So this is the shorter one from the father.
They couldn't be all on the left hand side but doesn't this all they have to be. And this is the shorter one from the mother. And I will draw this overlapping although they could have. Shorter one from the mother. And once again, each of these, this is a homologous pair, that's a homologous pair over there. Now, the DNA has been replicated so in each of the chromosomes in a homologous pair, you have two sister chromatids.
And so, in this entire homologous pair, you have four chromatids. And so, this is sometimes called a tetrad. So let me just give ourselves some terminology. So this right over here is called a tetrad or often called a tetrad. Now, the reason why I drew this overlapping is when we are in prophase I in meiosis I. Let me label this. This is prophase I. You can get some genetic recombination, some homologous recombination. Once again, this is homologous pair. One chromosome from the father that I've gotten from the father.
The species or the cell got it from its father's cell and one from the mother. And they're homologous. They might contain different base pairs, different actual DNA, but they code for the same genes. Over simplification, but in a similar place on each of these it might code for eye color or I don't know, personality.
Nothing is that simple in how tall you get and it's not that simple in DNA but just to give you an idea of how it is. And the reason why I overlapped them like this is to show how the recombination can occur.
So actually, let me zoom in. So this is the one from the father. Once again, it's on the condensed form. This is one chromosome made up of two sister chromatids right over here. And I drew the centromere, not to be confused with centrosomes.
That's where they are, those sister chromatids are attached. And then, I will draw the homologous chromosome from the mother. So the homologous chromosome from the mother just like that. Homologous chromosome from the mother. And the recombination can occur at a point right over here.
So after you're done with the recombination, this side might look something more like this. So let me draw it like this. So, they essentially break up and they swap those little sections. There's one way to think about it. So this one, we'll now have a little piece from the mother. It might code for similar genes.
But now it contains the mother's genetic information. And then this one over here will now have the piece. And you could say even homologous piece from the father.
Let me do these two centromeres. And this is really interesting.
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