How Do Recombination Frequencies Relate to Gene Distance?

[sonyab523]

Confused on 2 questions hereIf a recombination frequency between two genes is 1.5%, what is the distance between the genes in map units on the linkage map?

a. Impossible to determine, because the interference is not known.
b. 1.5
c. 3
d. 0.75

Recombination frequencies

a. arise from completely random genetic exchange.
b. are the same for all genes.
c. decrease with distance.
d. are the same for cis and trans heterozygotes.I thought it was b for the first part a for the second part and but I'm wrong. Can someone explain?

 

[sonyab523]

Sorry forgot to add my explanation

b. Each % frequency of recombination equals one map unit between the genes. So 1.5% recombination frequency = 1.5 map units apart will result in 1.5% recombination

a. It can't be (b), because genes are all distances apart; it can't be (c), because frequencies increase with increasing distance; it can't be (d), because the distance between genes is the same whether the alleles are cis or trans loci. So I thought it was a.

 

[sonyab523]

Help help please.

 

[nobahar]

I'm not absolutely sure, but I'd probably agree with your answers.

 

[sonyab523]

I'm not absolutely sure, but I'd probably agree with your answers.

I thought I was right but when I entered it into the system I was wrong. I'm sure the first part is right and I thought the second part was right but I guess not.

 

[epenguin]

I would probably agree too. It is a strange way of examining to ask which of four statements is correct. It seems to me though I am a bit rusty, that you have to a little bit psych what some of the questions mean, if it's any consolation.

 

[sonyab523]

Well that can't be right since it's marked wrong. Anyone think it's c for the second part?

 

[nobahar]

I don't think it's C.
I did think it may be D is the recombination frequency was being dtermined by phenotype. But, this seems less likely when I came across the following: http://books.google.co.uk/books?id=...e&q=recombination frequency cis trans&f=false
(Page 114)

 

[chemisttree]

I was thinking D and C. D because as the loci become further apart (low recombination values) the probability of a second crossover increases and the recombination value is overestimated. The only value less than 1.5 is 0.75 (D). I don't know what is meant by "interference" in answer A but that could be correct as well.

Edit. you are right C can't be correct

 

[sonyab523]

I finally found some material that helped. I got it right and the answer was D. Thanks guys for your help I really appreciate it.

 

[nobahar]

I've been talking about question 2.
For which one is the answer D? What did you arrive at for number 2?
The link I recommended explicitly states that trans and cis heterozygotes exhibit equal recombination frequencies.

 

[sonyab523]

I've been talking about question 2.
For which one is the answer D? What did you arrive at for number 2?
The link I recommended explicitly states that trans and cis heterozygotes exhibit equal recombination frequencies.

D is the answer for the second question. So you were right.

 

[nobahar]

D is the answer for the second question. So you were right.

My apologies, I lost track of the question! Technically I wasn't right, the textbook was...