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# Gene mapping

Discover the fascinating world of genetic recombination and gene mapping. Learn how the distance between genes on a chromosome influences their likelihood to recombine. Dive into the concept of centimorgans, the unit of measurement for gene distance, and how it relates to the frequency of recombination. Created by Efrat Bruck.

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• How would you determine where a gene is on a chromosome if you're given the number of offspring with certain phenotypes?
• Map distance between 2 linked genes = number of recombinants (offspring with certain phenotypes) / total number of offspring (times) 100.
• Hi, Is the video on gene mapping complete? I cannot see the statistical analysis part. Please let me know.
• At , the comment 'not drawn to scale' is made, but intuitively I don't think m.u. are a linear measurement of distance. For example, are the blue genes (B) and green genes (G) 31 (25+6) m.u. apart?
Am I right to say that the probability of recombination is the "probability of the blue swapping with respect to the purple and the green staying still" plus "the probability of the green swapping with respect to the purple and the blue staying still"?:
D(G->B) = ((1-0.06)*0.25 + (1-.25)*0.06)*100 = 28 m.u., which is not 31 m.u.
Any thoughts from others? Am I off base here?
• If you consider double cross-overs leaving the 'same' genetic product and other advanced genetics concepts, the accuracy of a map unit is reduced as you near 50 being the theoretical max. Since higher order cross-overs can happen in the genes that are not labeled, but do exist in between the labeled genes in her video, there is statistical analysis you can perform to prove the non-linearity as you near 50 cM. The take home message is that linearity approximates well for genes that are not separated by huge distances. You are correct in saying that linearity is not likely applicable for estimating genes which recombine at 31%.
• Thanks for a clear explanation in your video! I am looking for a more in-depth assessment of how map units relate to a specific % of progeny. e.g. if the resulting progeny is 4% (the # produced following crossing over*) Would the distance between loci = 8 m.u.? I read that the % of tetrads involved in an exchange b/t 2 genes = 2x the % of recombinant gametes produced. Is this the correct application of this formula, or am I confusing two related ideas?
*The cross is made with Ar/aR x ar/ar and only 4% of progeny are aarr. Thanks!
• Hi. Great video. I have a doubt regarding genetic recombination. Does genetic recombination occurs in non-coding regions, or it can happen anywhere in the chromosome? I think the latter would pose a problem if it occurs in the middle of a gene since the expression or the protein that it codes for could be compromised.
• I'm still not sure how to calculate Recombination Frequency, and I can't find a video on it. When you go to the questions, it says that I should watch this video, but this video doesn't tell me anything, I've watched it twice.
• When she says that recombination happens, is that something that occurs only during crossing over? Or are there other times this recombining can happen as well?
• Recombination is crossing over... two different terms meaning the same thing.
• Can the blue and green genes also recombine/separate?
(1 vote)
• Sure. I believe most of the genes along a chromatid can separate, or recombine. One of the important things to understand, though, is that the closer two genes are on a single chromatid, the less likely they are to separate.