Answer:
The<em> coefficient of interference, I, is</em> 0.1 (10% expressed as a percent)
Explanation:
Available data:
- genes for white eyes (w), cut wings (ct), and tan body (t) lie at map positions 2.00, 15.0, and 21.0, respectively
- Of 1000 progeny, 7 are double crossovers.
The<em> coefficient of interference, I,</em> is complementary with CC.
I = 1 - CC
To calculate the <em>coefficient of coincidence, CC</em>, we must use the next formula:
CC= observed double recombinant frequency/expected double recombinant frequency
<u><em>Note</em></u>:
- observed double recombinant frequency=total number of observed double recombinant individuals/total number of individuals
- expected double recombinant frequency: recombination frequency in region I x recombination frequency in region II.
By knowing the positions of genes, we can estimate the distances in MU between them per region.
- The distance between w and ct genes is 15 - 2 = 13 MU
- The distance between ct and t genes is 21 - 15 = 6 MU
Now that we know the distances, we can estimate the recombination frequencies by dividing each distance by 100.
- recombination frequency of w-ct region = 13MU / 100 = 0.13
- recombination frequency of ct-t region = 6MU / 100 = 0.06
Now that we know the recombination frequencies in each region, we can calculate the expected double recombinant frequency, EDRF, like this:
EDRF = recombination frequency in region I x recombination frequency in region II.
EDRF = 0.13 x 0.06 = 0.0078
Now, by knowing the total number of individuals in the progeny (1000) and the number of double crossovers (7), we can calculate the observed double recombinant frequency, ODRF:
ODRF = number of double crossovers / total number of individuals
ODRF = 7/1000 = 0.007
Finally, with the values of EDRF and ODRF, we can calculate the <em>coefficient of coincidence, CC.</em>
CC = ODRF/EDRF
CC = 0.007 / 0.0078
CC = 0.9
And by knowing the CC we can also get the <em>coefficient of interference, I</em>.
I = 1 - CC
I = 1 - 0.9
I = 0.1 = 10% (expressed as a percent)
