Recombinant alleles

[Function]

Hello everyone

 

This would be my very last question concerning genetics.

Imagine a crossing of an organism with genotype AaBb, and an organism with organism aaBb.

Between the alleles A(a) and B(b) is a distance of [math]2x\; cM[/math].

What is the chance of getting an organism with genotype Aabb?

 

[math]\begin{tabular}{|c||c|c|c|c|}\hline & AB & Ab & aB & ab \\ \hline\hline aB & AaBB & AaBb & aaBB & aaBb \\ \hline ab & AaBb & Aabb & aaBb & aabb \\ \hline aB & AaBB & AaBb & aaBB & aaBb \\ \hline ab & AaBb & Aabb & aaBb & aabb \\ \hline \end{tabular}[/math]

 

Now, in order to solve the question, I have to know which of the alleles of both organisms are recombinant. How can I do this?

 

Thanks!

 

Function

Edited April 23, 2014 by Function

[vampares]

The term you are looking for is 'recombination'. Recombination occurs at gameteogenisis. When the the two chromosomes of one cell are distributed between two gametes, the DNA can be interchanged from one chromosome to the other. This is not a complete shuffling (as far as I am aware) and I don't know that it follows a distinct interval. There may be more information available.

 

You don't need to know how many recombinations there are if you can safely assume that a recombination would occur. Mathematically that is not exactly correct, even though we don't know how many recombinations will occur.

 

I don't know what 2x cM is. Although you see that there is a 50% chance A and a 25% chance for B. 12.5% chance if this is not the same chromosome. OK on chromosome, say there are 100 recombinations, (I have no idea what 2x cM means) that is a one in hundred on a 50% we are on the wrong chromosome to begin with. "Worst case" scenario 6.25%. Realistically, scrambling your DNA not the most important thing in life. eh? > 6.25%

Edited April 23, 2014 by vampares

[Function]

[math]2x \; cM[/math] is [math]2x[/math] centimorgans, or a recombination frequency of [math](2x)\%[/math]. This means that there is a chance of [math]x\%[/math] per recombinant allele to 'exist' as a consequence of crossing-over. I'd just like to know which allele is recombinant and which is not.

Edited April 23, 2014 by Function

[vampares]

"recombination frequency" per codon or per chromosome? OK centimorgans nevermind.

 

 

 

Once a cross over is done, I thought recombination was done on a branch level. Like two chromosomes ( | being a recombination)

 

 

OOOO|OOOOOO
XXXX|XXXXXX

OOOO|XXXXXX
XXXX|OOOOOO

 

as opposed to a 'splice' of the DNA -- which would actually be the result of two recombinations. I searched this topic a while ago and never found a any explicit proteins or enzymes which regulated the recombination. It seemed to just occur as a function of gametes.

 

So glass is half empty, glass is 40% full.

 

 

The distance is important

 

 

 

far 7 possible recombination points, 70% chance per recombination
OAOOOOOObO
XaXXXXXXBX

close 1 possible recombination points, 10% chance per recombination
OAbOOOOOOO
XaBXXXXXXX

Or could be

 

far
OaOOOOOObO
XAXXXXXXBX

close
OabOOOOOOO
XABXXXXXXX

The heredity of the pheno-genotype would be able to eventually give you this information. Or not?

 

The fact that one successful recombination in the far example leaves 6 possible recombinations points to reverse the prior one is trivial I suppose. In the close example, assuming recombination was a one time event, the success could not be reversed.

 

In the case of mulattoes, i.e. black X white, for example Barack Obama, there are many pigmentation encodings in the human genome.

 

The first cross would have all locus in hybrid.

 

The second cross would present the possibility of recombination. This would be required for one chromosome to posses homozygous locus of alleles.

 

Whence the mandatory minimum sentencing crack laws

Edited April 23, 2014 by vampares

[Function]

Forgive me my behaviour, which might seem arrogant, but what you say is irrelevant to my question: I'd like to know which one of the possible gametes of organism 1: AB, Ab, aB, ab; are recombinant, and also for organism 2: aB, ab, aB, ab to decide the chance of getting one of the genotypes in the table I gave in #1.

 

What you say is undoubtedly very interesting, but has little to do with my question, as far as I'm aware of.

Edited April 23, 2014 by Function

[vampares]

Recombination of any sort... perhaps this is a different topic of discussion...

 

Outside of sexual reproduction, does this still occur? Or are chromatids otherwise preserved outside of the gametes?

Behavior is not my policy.

 

which one of the possible gametes of organism 1: AB, Ab, aB, ab; are recombinant, and also for organism 2: aB, ab, aB, ab to decide the chance of getting one of the genotypes in the table I gave in #1

 

In sexual reproduction there is no way of knowing whether or not recombination has occurred per gamete (think sperm under a microscope).

 

In the event of a successful recombination the genetic signature of the parentage (if there is one) can be compared to the adjacent genetic material. This is only possible if chromatids are preserved prior to gameteogenesis. I think they are.

 

OK so that is post facto. If the genetic locus of the parentage is not known, more intensive phenotype analysis of heredity (parents and/or offspring) would be required. This is assuming there are traits close enough to the loci to minimize the event of inadvertent recombination.

 

I would ask how we know the allele is on the same chromosome in the first place? Obviously parentage would have indicated the differing chromatids.

 

Anyways it is between Aa|Bb. The DNA is preserved, but it is in two gametes, now there is a 50% chance the right sperm or egg involved in reproduction. (sort of like the movie Twins)

What you need to know, if this is an academic question is what x is. Should the answer contain the x variable?

Edited April 23, 2014 by vampares

[Function]

vampares

 

Note that I'm in my last year of high school, about to participate in the approval exam for med school. Nothing was meant to be as complicated as you make it.

Assume that the alleles A(a) and B(b) are on the same chromosome.

Let AaBb be the genotype of the first organism. Possible gametes are AB, Ab, aB and ab. Which of those are recombinant and which are not?

 

[math]x[/math] is just a random, even number between 0 and 100, expressing the recombinant frequency, expressed in percentage or centimorgan. I just called it [math]x[/math] because I was tired of always using the same "20 cM"

Edited April 23, 2014 by Function

[vampares]

I would go about this with a proportion equation

 

locus distance

--------------------------------------- =

average recombination length

 

x

----

.01

 

the 12.5% is contingent upon the recombination percentage. x% * 12.5%. err well I guess its not now. x% * 25%.

 

I'm not sure where the 2 came in.

Edited April 23, 2014 by vampares