Gene linkage/recombination

[AntonFreeman]

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When the question says gene for color and size are located on same chromosome, how do we know which alleles are together? I am looking at TPR books. Some questions do not tell you which alleles are linked together.

 

[ilovemcat]

When the question says gene for color and size are located on same chromosome, how do we know which alleles are together? I am looking at TPR books. Some questions do not tell you which alleles are linked together.

Don't take my word on this, but I believe if the percent recombination is 50% or greater, then they are considered to be unlinked because they have a higher probability of swapping places with a neighboring chromatid. A lower percent recombination indicates they are more likely to remain linked together.

 

[GreenRabbit]

You cannot have a recombination frequency greater than 50%.

At 50% the genes are said to be unlinked.

 

[flodhi1]

When the question says gene for color and size are located on same chromosome, how do we know which alleles are together? I am looking at TPR books. Some questions do not tell you which alleles are linked together.

The further the genes are the more chances of recombination. Here's a brief description of how this works

2 Genes Far apart on the same chromosome leads to crossing over between genes in every meiosis there is a 50 % recombinant progeny and the genes are defined as Unlinked.
2 Genes on different chromosomes have independent segregation of different homologous pairs and also have a 50 % recombinant progeny and the genes are unlinked.
When 2 genes are intermediate distance apart on SAME chromosome then crossing over occurs between genes in some meiosis which leads to < 50 % recombinant progeny. Genes are classified as partially linked.
When 2 genes are VERY close together on SAME chromosome No crossing over occurs there's 0 % recombination and genes are classified as linked.

So chances of recombination go any where from 0-50 % depending on the situations that I listed above. There WILL NOT be recombination more than 50 % that is the max

 

[AntonFreeman]

Thanks for responses. But what I saw on TPR was that unless specified, it seemed like dominant alleles are always on same chromosome and recessive alleles are linked together (ex BG bg).