Agron 527
Homework #1
Due 2/1/02
Marks: 10
Mendel probably failed to observed linkage between stem length (le) and pod shape (p or
v) for one of the following two reasons.
• Pod shape trait studied by him was governed by p, not by v that is linked to le.
• Mendel studied a small F2 population to study the di-hybrid segregation of le and
v.
Assuming that the second scenario is correct, what are the possible explanations to justify
Mendel’s failure to detect the linkage between le and v loci?
Considerations to make:
1. The genetic distance between the two loci was 12 cM.
2. The mutation rates for both genes were zero.
Homework #2
•
•
Due 6 PM, 2/7/02
Marks: 10
Resistance of soybean to the bacterial pathogen Pseudomonas syringae pv.
glycinea (Psg) is conferred by major resistance genes (Rpg). You are to study the
inheritance of resistance in soybean against this pathogen as a graduate student.
Resistance is dominant over susceptibility.
•
It is not clear whether the resistance of soybean to Psg race 1 is conferred by a
single or two Rpg genes.
•
If there are two genes responsible for resistance, then assume that at least a single
copy of each gene (wild type functional copy) is required to result resistance
against this race.
•
Assume that there is no linkage between the possible two Rpg genes.
•
What would be the minimum population size (F2) that you would like to
evaluate in order to determine the number of genes that confer resistance of
soybean against Psg race1?
•
Develop your hypotheses for the inheritance study after determining the
minimum number of F2 plants required in your investigation.
Homework #3
Due 3/4/02
Marks: 20
•
Please make a summary of the most important points to remember from the
review paper: http://www.plantcell.org/cgi/reprint/12/5/617.pdf (also can be
found in our web page = paper to read).
•
Please make a list of the materials that needs clarifications (if any).
•
Please read individually. It's encouraged to discuss with your partners during
preparation of the summary. A group summary will be acceptable (Please submit
the summary by e-mail + hardcopy). No page limit for the summary.
•
This paper is a part of the course. I hope this paper will help you to get a better
idea of the genome organization.
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Homework # 4
Due 3/8/02
25 marks
(Hypothetical examples!)
Q 1.
Crosses between red and white flowering cultivars of green beans were made and
following results were obtained.
1. P1 (red color) x P2 (white color)
= F1 (red color) = F2 segregates to 9:7: : red:
white flower colors.
2. P3 (white color) x P4 (white color) = F1 (red color) = F2 segregates to 9:7:: red:
white flower colors.
3. P5 (red color) x P6 (white color)
= F1 (red color) = F2 segregates to 3:1:: red:
white flower colors.
Parents were homozygous. A metabolic pathway elaborates the red pigment found in red
flower.
•
•
Write the genotypes of the parents (P1, P2, P3, P4, P4, P5, and P6) assuming no
linkages between genes.
---5 marks
Develop a model for each of the crosses to explain the flower color development
in F1 and F2 generations.
---5 marks
Q2.
In peas round seed shape is dominant over wrinkled shape and red flower color is
dominant over white. Both traits are governed by single genes. We have to analyze
results obtained from the following two crosses.
1. P1 (Round seed, red flower) x P2 (Wrinkled seed, white flower)
F1 (round, red)
F2 segregation:
Round seed and red flower
= 450 plants
Round seed and white flower
= 80 plants
Wrinkled seed and red flower
= 75 plants
Wrinkled seed and white flower
= 115 plants
2. P3 (Round seed, white flower) x P4 (Wrinkled seed, red flower)
F1 (round, red)
F2 segregation:
Round seed and red flower
= 450 plants
Round seed and white flower
= 220 plants
Wrinkled seed and red flower
= 235 plants
Wrinkled seed and white flower
= 5 plants
Carry out the necessary statistical analysis to test if there are any linkages between these
two traits in these two crosses.
-- 5+5 = 10 marks
Q3.
The following F2 segregation data are provided by your major professor for statistical
analysis. He does not know about the mode of inheritance of genes that control plant
height and nematode resistance in this cross in tomato. He wonders if these two traits are
linked.
F2 segregation
Tall plant and resistant to nematode
Tall plant and susceptible to nematode
Dwarf plant and resistant to nematode
Dwarf plant and susceptible to nematode
= 550
= 100
= 80
= 150
Carry out a suitable statistical analysis to determine if there is any linkage between plant
height and nematode resistance.
-- 5 marks