Questions tagged [crossover]

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If crossing over can cause formation of new allele, can it affect Hardy-Weinberg equilibrium?

I was reading about Hardy-Wienberg equilibrium on Wikipedia and there are seven assumptions underlying HW It is mentioned that sexual reproduction one of the assumption and is a must for HW, but ...
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1answer
118 views

What is the map unit between the genes?

While doing some biology I came across this question: The following tables present results of plant crosses involving two linked genes: S is a seed-color gene, and L is a plant-height gene. Each gene ...
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2answers
279 views

How do gene locations change during crossing over events?

Suppose you have two variants from the same species, which have slightly different chromosomes I's to each other. Genes may be in slightly different positions on the chromosome, and the lengths of the ...
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1answer
49 views

How many of the four meiotic daughter chromosomes of a homologous pair can be recombinant via crossover?

In graphics I've seen, crossing over occurs between the "inner" two chromatids in a side-by-side arrangement of two duplicated chromosomes: This suggests that only two of the four meiotic daughter ...
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2answers
57 views

Crossover Value and Genetic Mapping [closed]

In my textbook and most of the sources I have checked, it is stated that recombination frequency in eukaryotes give us knowledge on the location of the loci. I don't understand the direct correlation ...
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0answers
61 views

What is the probability that a gamete will only contain father's chromosomes

As it is depicted in most textbooks, cross-over does not occur between the two "outer" sister chromatids. By independent assortment during Meiosis I, there is 1/2^23 chance that all father's ...
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13 views

How does a neutral allele change relative to a nearby allele under selection?

Suppose I'm looking at a gene being selected against (A) that's decreasing at a rate ($\Delta$P). If there's a nearby allele that is neutral (B) am I correct to assume that B will decrease with A at a ...
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32 views

How did the molecular machinery for recombination originate?

I'm wondering about the origins of genetic recombination. During crossover new chromosomes are created. They have different allele combinations from the original two chromosomes. This process allows ...
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3answers
142 views

Can chromosomal crossover undo itself?

If I have alleles AB on one chromosome and ab on another, and if A and B are far from each other (and also a and b), then there is a lot of chromosomal crossovers happening. If I crossover 7 times, ...
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1answer
2k views

Why does chromosome inversion happen?

I read that chromosome inversion is a type of genetic mutation. Why does inversion happen? What is the purpose? I also read that if genes do not match up during cross over between inverted ...
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1answer
330 views

Does crossover happen between chromosomes from grandparents?

Rephrasing question: does crossover happen after sperm and egg meet each other, but before formed fetus starts to grow? As I understand sperm and egg of human are haploid cells. That means this cells ...
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1answer
960 views

Why does crossing over take place at all?

I already know that crossing over causes genetic variation. My question is that since DNA is a stable molecule, why would it undergo process like crossing over during which it becomes so unstable and ...
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2answers
877 views

Does chromosome cross occur over male and female or vice versa? [closed]

My understanding is homologous chromosome pair, which means male and female chromosome inside the DNA. So if that's homologous how does male do with female? Does it flip over and change direction, ...
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1answer
89 views

A diagram of a crossover [closed]

How can one draw a crossover between ABK and aBk where genes A and B follow the Mendel's law of independent assortment and gene K does not i.e. K is linked to B?
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1answer
1k views

When do 3 germ layers form in embryo? And why is there only one mature egg formed?

During the process of pregnancy, when do the 3 germ layers form in embryo? Is it after formation of gastrula? Also, during oogenesis, why does only one mature egg form? Why don't use polar body egg ...
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Why only human have noticeable difference in face? [duplicate]

Our facial appearance is pretty much different from each other unless we are talking about twin. Credit goes to crossing over of chromosome. But why can't we distinguish between other animals of same ...
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1answer
740 views

Why does allele linkage cause disproportionate phenotypic ratios? [closed]

I was learning about allele linkage in Biology class and I got confused by the resultant phenotypic ratios. Say you have a dihybrid cross BbGg x BbGg. The Punnett square would look like the ...
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4answers
599 views

How does the molecular machinery choose where to cut a chromosome for recombination?

I'm wondering about a few technicalities of crossover in meiosis. The point of crossover is to create new chromosomes that don't have the same allele combinations as the original two chromosomes. ...