Biology 2581B Study Guide - Midterm Guide: Dna Mismatch Repair, Centrosome, Dna Replication

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19 Apr 2016

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See question 19 & 42 on sample questions. [type a quote from the document or the summary of an interesting point. You can position the text box anywhere in the document. Text box tools tab to change the formatting of the pull quote text box. ] In a certain plant there is a gene b/b with 2 alleles (b=blue; b=cream coloured flowers). 31. second gene t/t can act to suppress cream flower colour. Allele t has no suppressor allele t suppresses expression of allele b producing a wild-type phenotype. suppressor effect on the b allele. The two genes are unlinked and both show complete dominance. What phenotypic ratio would you expect if you testcrossed a plant that is bbtt? b. c. d. e. Cross 2 d g / d g x x d g / d g d g / d g. The f1 from cross 1 is crossed with the f1 from cross 2.

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11. You suspect that two genes interact with one another to determine the product of a pathway you are studying. You cross two pure breeding plantsâone with white flowers and one with pinkâto make F1 individuals that have blue flowers. You cross the F1 generation and observe the following numbers of individuals with different phenotypes: Number of individuals Phenotype 91 Blue 30 Pink 39 White Which pathway best explains these results? (Note that arrows indicate enzymatic reactions carried out by products of genes 1 and 2. Assume that buildup of metabolites will determine flower color.)

Question 12 and 13: Consider the biochemical pathway presented below. This pathway determines pigment production in pea flowers. (Note: gene products are required for each reaction to proceed.)

12. Do you expect that genes A and B will interact with one another?

A. Yes B. No C. Insufficient information to determine

13. What phenotype ratio would you expect in offspring produced by crossing AaBb parents?

A. 9:3:3:1 (blue : green : yellow : white) B. 9:3:4 (blue : green : white) C. 9:7 (blue : white) D. 15:1 (blue : white)

14. How can haplosufficiency explain dominance of an allele that codes for a functional protein over a null (loss of function) allele?

A) a single functional copy of the gene produces sufficient gene product for normal biological function B) a single functional copy of the gene produces insufficient gene product for normal biological function C) the null allele produces a product that interferes with proper function of the normal allele D) the null allele produces a product that does not interfere with proper function of the normal allele E) the null allele rapidly mutates to reacquire normal functionality

15. In a plant species with genes A and B, you have isolated recessive mutant alleles at each locus, which you call a and b. You would like to know whether these two genes are linked. To test this hypothesis, you obtain an individual that is heterozygous at both genes (AB/ab) and perform a test cross. Which results would be most consistent with these loci being tightly linked? (Results are counts of the numbers of offspring from the testcross.)

A. Ab/ab 390 aB/ab 410 AB/ab 350 ab/ab 420

B. Ab/ab 80 aB/ab 73 AB/ab 760 ab/ab 754

C. Ab/ab 700 aB/ab 695 AB/ab 56 ab/ab 59

D. Ab/ab 400 aB/ab 65 AB/ab 50 ab/ab 659

goldclam880

Problem A. You cross two homozygous parents: RRYY (round yellow) and rryy (wrinkled green) to produce an F1 generation. Round seeds are dominant, yellow seeds are dominant. You cross two F1s to produce the F2 generation. In the F2 generation, you find an individual with round yellow seeds. You do a testcross to find out the genotype of this âmysteryâ dominant/dominant phenotype. In the offspring of the cross, you find 1?2 have round yellow seeds and 1?2 have wrinkled yellow seeds.

1. Based on these data what was the genotype of the mystery F2?

Problem B. You carry out a dihybrid cross between a red-flowered rose with long pollen grains (A1A1 LL) and a white-flowered rose with round pollen (A2A2 l l). The flower color gene (A) shows incomplete dominance, and long pollen is completely dominant to round pollen. The genes for these traits are on different chromosomes so assort independently

2. What would be the phenotypes of the F1 generation?

3. What fraction of the F2 generation is expected to have red flowers and long pollen? (As always when traits are independent, what rule can you apply to save time?)

Problem D. In the example of epistasis presented in class, the agouti allele in mice (A) codes for striped hairs and is dominant to the allele for all black hairs (a). A loss-of-function allele for the pigment gene (b) produces no pigment and is recessive to the normal, dominant allele (B). The recessive allele at b masks the effect of the A gene. A dihybrid cross of AABB and aabb is carried out.

5. Name all of the genotypes in the F2 generation that can produce an albino (no pigment) phenotype.

Problem E. A cross is made between homozygous fruit flies that differ for eye color (the st gene) and

body color (the e gene). The F1 double heterozygote is shown below using chromosome notation.

st+ e

--------------------------------------

st e+

st = the recessive allele for scarlet eyes; st+ = the dominant wildtype allele for red eyes e = the recessive allele for ebony body; e+ is the dominant wildtype allele for gray body

6. Are the chromosomes shown in the genotype above in cis or trans configuration?

7. Based on this notation, what were the genotypes and phenotypes of the two parents of the F1? (Think carefully here...)

8. With what phenotype would you cross this F1 to measure recombination frequency?

cyansnail823

Suppose that red flower color (A/A or A/a) is dominant to white flower color (a/a) in petunias. The common allele (A) encodes the red pigment for petal colour. The rare allele (a) encodes a nonsense mutation in the pigment gene, so no pigment is produced (such that petals are not coloured and appear white). Among the petunias in a greenhouse population, 480 are A/A and 90 are A/a. There are no white-flowered petunias observed. Is this population of petunias in genetic equilibrium? Show all of your steps and calculations clearly (including use of a Ï 2 test) and write a brief (2-3 sentence) conclusion about whether this population of petunias is in HardyâWeinberg equilibrium. Make sure the expected genotype frequencies equal to 1

You have selected a petunia plant from the greenhouse with red flowers and want to determine whether the plant is A/A or A/a.

a) What kind of experiment (what kind of cross) could you perform to determine the genotype of the selected petunia plant? Explain briefly.

b) How will the cross in (a) help you determine the genotype of your red-flowered petunia? That is, explain how will the results from this cross differ if the red-flowered petunia is A/A versus A/a?

c) You end up choosing two red plants that are both of the genotype A/a and you cross them. If the cross produces six plants, what is the probability that four of them will be white and two will be red?

MY ANSWERS SO FAR

Allele frequency of p= 1/2 (2pq)+ p²

P= 1/2 (0.1578) + 0.8421

=0.921

Allele frequency of q = 1/2 (2pq) + q²

⁼ 1/2 (0.1578) + 0.0

= 0.0789

Expected genotype of the population:

AA(p2)= 0.848 aa (q2)= 0.006

(2pq)Aa =0.0105

I'm confused as to why this doesn't total upto 1

goldcrab34

Biology 2581B Study Guide - Midterm Guide: Dna Mismatch Repair, Centrosome, Dna Replication

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