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A few genetics questions

Genetics as it applies to evolution, molecular biology, and medical aspects.

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A few genetics questions

Postby susy15 » Mon May 10, 2010 6:31 pm

Hi,
I'm new to this website - I am currently taking an online Genetics course and am finding it very difficult. In fact, I have contacted a few genetics tutors from the local university and none of them seem to be able to help me with my assignments as they are mostly genetics analysis problems. So, hopefully someone here will be able to help me. Here are a few questions from my current assignment:
1. Suppose that a dwarf plant that is homozygous lele is crossed with a dwarf plant that is homozygous le-3le-3, which of the following germs best describes the genotype of the F1 offspring?
-homozygote
-lethal heterozygote
-compound heterozygote *I chose this one because I know the offspring will be heterozygote and since they're both
dwarf, I think that compound would be the correct term

-pleotropic heterozygote

2. Which of the following terms best describes the expected phenotype of the F1 offspring from the cross described in the above question?
-tall
-dwarf *I chose this one because there is no dominant tall genotype from the parents
-intermediate between tall and dwarf

3. Suppose that the F1 plants from the corss described in the above question are allowed to self-fertilize. What proportion of the F2 plants is expected to be dwarf?
-0
-1/16
-1/8
-3/16
-1/4
-1/2
-7/16
-3/4 *I chose this one because 1/4 will be tall according to my punnett square
-9/16
-1

4. To determine whether or not there was a difference for genetic segregation in pollen and egg cells, Mendel conducted four experiments using the genes that governed seed shape and seed color. For the purposes of this experiment, we’ll use the modern symbols for the alleles of these genes: R and r for the alleles that govern seed shape, and I and i for the alleles that govern seed color (see figure 12.13 on page 362 of your textbook). The four experiments consisted of the following crosses (the female parent is listed first in each cross):
Experiment 1: RrIi × RRII
Experiment 2: RrIi × rrii
Experiment 3: RRII × RrIi
Experiment 4: rrii × RrIi
He recorded the following phenotypic results for the progeny of these crosses:
Phenotypes
Experiment Round, yellow Round, green Wrinkled, yellow Wrinkled, green
1 98 0 0 0
2 31 26 27 26
3 94 0 0 0
4 24 25 22 27

Compare the results of experiments two and four - which of mendel's principles are illustrated by these results?
- segregation only
- independent assortment only
-parental equivalence only
-segregation and independent assortment only
-segregation and parental equivalence only
-independent assortment and parental equivalence only
-segregation, independent and parental equivalence *I chose this one because I think it demonstrates all of the principles

5. There was only one phenotype among the progeny in experiments one and three. How many genotypes are there among the progeny of experiments one and three if the results of these experiments are combined?
-(choice of 1-8)
*I chose 2: RrIi and RRII

6. There were four phenotypes among the progeny in experiments two and four. How many genotypes are there among the progeny of experiments two and four if the results of these experiments are combined?
-(choice of 1-8)
* I chose 4: RrIi, rrii, Rrii, rrIi

7. Conduct a chi-square test of the results of experiment two to test the hypothesis that the results conform to those expected from the parental types listed. Which of the following is closet to the correct chi-square value?
-(choice of 0-4.0 by increments of 0.5)
*I chose 0.5, using # of individuals observed = 2, # expected = 4

8. How many degrees of freedom are there in the chi-square test conducted for the previous question?
-(choice of 1-8)
*I chose 4 from the set up of the chi-square test

9. What is the appropriate conclusion derived from this chi-square test?
- Reject the hypothesis
- Do not reject the hypothesis
- The results are ambiguous, we can neither reject nor fail to reject the hypothesis
*I chose Do not reject the hypothesis because from the results we can't reject it

Please let me know if my answers are correct. It would be greatly appreciated! Thank you!
susy15
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Postby JackBean » Mon May 10, 2010 6:57 pm

Just 9 short questions?

If I understand it correct, both alleles are of the same gene, so you shouldn't have any tall plants either in F1, neither in F2, as you have nowhere where to take allele for tall growth

IMHO the answer for 5 and 6 should be the same ;)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Re: A few genetics questions

Postby susy15 » Tue May 11, 2010 12:03 pm

Thanks for your reply, can anyone else help as well?? I'm in desperate need of help!
susy15
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