three-point

three-point - The 3-point test cross Mapping three(linked...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
The 3-point test cross • Mapping three (linked) loci • Inferring gene order • Interference – Is the frequency of double-crossover less than expected? • Map functions – Translating c = freq(recombination gametes) into the expected number of crossovers m. Double crossovers • When considering three loci, we can observe double crossovers that would have been missed if only two loci are followed • Hence, the frequency of “recombinant” gametes underestimates the actual frequency of crossingover. The three-point testcross The mapping (and analysis) of three linked loci
Background image of page 1

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

View Full DocumentRight Arrow Icon
Testcross as only st e ss gametes from This parent These are the two parental gametes (being the most Common) For three-point analysis, key is to consider EACH PAIR of loci separately ! st - e locus pair Parentals: st + e + , st e st + e --> recombinant st e + --> recombinant st + e --> recombinant st e + --> recombinant st + e + --> parental st e --> parental Freq(recom) = (50+52+43+41)/755 = 0.246 e - ss locus pair Parentals: e + ss + , e ss e ss --> parental e + ss + --> parental e ss + --> recombinant e + ss --> recombinant e + ss --> recombinant e ss + --> recombinant Freq(recom) = (5+3+43+41)/755 = 0.122
Background image of page 2
st - ss locus pair Parentals: st + ss + , st ss st + ss --> recombinant st ss + --> recombinant st + ss + --> parental st ss --> parental st + ss --> recombinant st ss + --> recombinant Freq(recom) = (50+52+5+3)/755
Background image of page 3

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

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 7

three-point - The 3-point test cross Mapping three(linked...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online