Ro_Lecture6 - Lecture 6 A geneticist isolates two mutations...

Info icon This preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Lecture 6 A geneticist isolates two mutations: A = tall a = short H = hairy h = no hair and constructs the following pure-breeding stocks: AAhh and aaHH. These individuals are mated and the F1 progeny are mated to the double recessive. The following results are obtained in the F2: Do these genes reside on the same or different chromosomes? Answer- Same- linked If they reside on the same chromosome, what is the distance between them? We simply must identify the parental and recombinant classes and determine the recombinant frequency #Recombinants/Total progeny
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 P AAhh x aaHH A h x a H A h a H F1 AaHh x aahh A h x a h a H a h Parental Recomb
Image of page 2
3 Which are the parental and which are the recombinant classes? What is the recombination frequency? So the map distance between the A and H genes is 410+415 825 =29% 410+1007+987+415 2819
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
4 Another mutation C (crinkled) is isolated and recombination frequencies between this gene and the A and H genes are determined % recombinants A to H 29 A to C 15 H to C 16 A H C 29 15 16 15+16=31 not 29
Image of page 4
5 What is going on? The map is not internally consistent? ---A-------H------------------ ---A-------H------------------ ---a-------h------------------ ---a-------h------------------ A-H parental A-h Recomb a-H Recomb a-h parental ---A--------------------H----- ---A--------------------H----- ---a--------------------h----- ---a--------------------h----- A-H parental A-H parental a-h parental a-h parental Single cross-over Double cross-over The parental class is over counted for progeny with 2 crossovers The recombinant class is under counted for the progeny with two crossovers Over large distance there will be a significant number of double crossovers that go undetected:
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
6 The double crossovers go undetected and therefore over large distances the genetic distances are underestimated The solution is to include intervening markers to greatly reduce the probability of undetected doubles: For instance with the intervening C marker the double
Image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern