Can Anyone Help on Biology Problems?

Test Preparation SAT Subject Test Preparation
1

<p>I don't know ho to do double crossing....
Here are sample questions, could anyone explain or just show their work, thanks</p>

<ol>
<li>Mice have genes for coat color, eye color and whiskers all on the same chromosome. We will call the three genes I, C, E. Below are the data from the cross of two different mice. First determine which are the parents and which are the double cross-over events, then figure out the two sets of single cross-overs to then order the genes and their map distances. (1605 total mice from the parents).</li>
</ol>

<p>Phenotype#
ICE 17
iCE 499
icE 198
IcE 89
iCe 89
Ice 15
ice 501
ICe 197</p>

<ol>
<li>We have recently discovered another strange “unintelligent” life form. We know that unibrow, wings and horns are all dominant (B, W, H). Di-Brow, wingless and hornless are recessive. We will attempt to map part of one of its chromosomes. The following data is from a test cross with a heterozygote. There are 2000 offspring. Order the genes and find their map distances.</li>
</ol>

<p>Phenotype#
BWH 589
bwh 581
BWh 49
bwH 56
Bwh 245
bWH 257
BwH 110</p>

2

<p>I’ll show how to do 2nd one, then u can figure out solution to 1st one.( actually, 1 phenotype missing,but it’s easy to find that one) </p>

<p>parental types-BWH+bhw</p>

<p>single-cross-over between B and H–Bwh+bWH–245+257=502</p>

<p>single-cross-over between H and W–BwH+bWh–110+113=223</p>

<p>double cross-overs-BWh+bwH–49+56=105</p>

<p>to find distance between B and H-> (502+105)/2000=0.3035 (x 100)</p>

<p>… … … … H and W->(223+105)/2000=0.164 (x 100)</p>

<p>So, we know that order is like B---------30------H—16.4----W</p>

<p>That’s about it!</p>