genetics-silkworms

[chousta]

hey all.

im havin some troubles with a question from an exercise, and it doesn't have a solution, but ive made an attempt, hoping its right and someone could lead me the right way for the next part of it.

Question:



a) I addressed this question talking about each phenotype rather than 2 variables?

anwys.

genetic hypothesis 1:
A single pair of alleles determine haemolymph colour, the allele producing yellow colour being dominant (since yellow is most frequent in F2). Therefore, the F2 should show a ratio of 3 yellow: 1 white. Any deviation from this ratio is due by chance.

This is the case


genetic hypothesis 2:
A single pair of alleles determine surface pattern, the allele producing lined surface pattern being dominant (since lined surface is most frequent in F2). Therefore, the F2 should show a ratio of 3 lined: 1 plain. Any deviation from this ratio is due to chance alone.

Calculations:

Phenotype Lined Plain
Observed 374 106
Expected 360 120


X^2=Sigma ((O-E)^2)/E
= 2.18

Determining Factor=2-1=1

Probability statement:
From above, the probability of obtaining as great deviation between expected and observed, by chance alone, is greater than 0.05, therefore we accept that the deviation from 3:1 is attributed to chance

Biological statement:
Therefore we do not reject the single dominant gene hypothesis




B)No not ALL, would have the same phenotype, because this would not highlight the nature of genetics. I.e. dominant and recessive.

No idea for the rest.
Im taking a second year genetics course, but im actually a first year student....so if you could look past my lack of understanding, which is probably all very trivial to you.


thank you very much for your time.

[mith]

erm, I think your answer for B is wrong. When in doubt, draw out the punnets.

[Cat]

I posted answer on my website:

http://science-ed.fullsubject.com/1-on- ... 52.htm#135

Good luck!