Lectures

How to Avoid Missed Double Crossovers – Gene Mapping

by Georgina Cornwall, PhD
(1)

Questions about the lecture
My Notes
  • Required.
Save Cancel
    Learning Material 2
    • PDF
      Slides 04 GeneMapping Genetics.pdf
    • PDF
      Download Lecture Overview
    Report mistake
    Transcript

    00:01 A way to go about avoiding this miscalculation or limiting the amount of air is by adding additional cross point. For example, we could look at a three point cross or four or a five point cross. Here is the example. Let us say we are looking at genes A and B and if we were looking at this example, we have a double crossover event where we definitely have a recombination for the B allele, but A and C appear like there was no crossing over event at all. So we are going to estimate that they are closer together, but by examining an allele that is in between A and B, we can look at the frequency of recombination between A and B and between C and B as well as between A and C to figure out more precisely what those relative distances are. We will have better estimates of our map distances. Now the more low side we look at in these recombination frequency calculations, the better estimates we have of map distances along the chromosome. Here we are looking at genetic maps. Later on, we will start looking at physical maps, which give us actual locations and we can do that much more readily now because we actually have the sequence of the genome to work with.

    01:32 But prior to genome sequencing, we relied primarily on or we relied all the way on genetic maps. Genetic maps in humans clearly could be a little bit challenging because we have so many chromosomes, so many linkage groups to think about that sequencing them all or estimating distances for them all could be very tedious. For example, on the X chromosome, we have over a thousand known genes mapped in place and in order to get recombination frequencies in humans, we also have a pretty long generation time. We have to look at historical perspectives of what might have happened to get any estimates. Although it is not possible, it certainly not very easy to use genetic mapping techniques on human genome. However,


    About the Lecture

    The lecture How to Avoid Missed Double Crossovers – Gene Mapping by Georgina Cornwall, PhD is from the course Understanding Genetics.


    Included Quiz Questions

    1. 9.8 cM
    2. 0.98 cM
    3. 90.2 cM
    4. 9.02 cM
    1. It results in shorter recombination frequencies and can be avoided by examining a three-point cross.
    2. It results in longer recombination frequencies and can be avoided by examining a three-point cross.
    3. It results in shorter recombination frequencies and can be avoided by using microscopic techniques.
    4. It results in longer recombination frequencies and can be avoided by examining a two-point cross.

    Author of lecture How to Avoid Missed Double Crossovers – Gene Mapping

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD


    Customer reviews

    (1)
    5,0 of 5 stars
    5 Stars
    5
    4 Stars
    0
    3 Stars
    0
    2 Stars
    0
    1  Star
    0