Gene Mapping Techniques Question Paper

Gene Mapping Techniques

Course:Bachelor Of Science

Institution: Kenyatta University question papers

Exam Year:2009

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2009/2010
FIRST SEMESTER EXAMINATION FOR THE DEGREE OF SCIENCE
(BIOTECHNOLOGY)
SBC 315: GENE MAPPING TECHNIQUES

DATE: WEDNESDAY, 23RD DECEMBER 2009
TIME: 8.00 A.M. - 10.00 A.M.

SECTION A 40 Marks: Answer Any Two Questions
1.
a)
Distinguish between the ways by which gene transfer is effected in conjugation

and transduction mapping.

(7 Marks)

b)
In an Hfr × F- cross, leu+ enters as the first marker, but the order of the other

markers is unknown. If the Hfr is wild type and the F- is auxotrophic for each

marker in question, what is the order of the markers in a cross where leu+

recombinants are selected if 27 percent are ile+, 13 percent are mal+, 82

percent are thr+, and 1 percent are trp+?

(3 marks)

c)
Order the genes cheA, cheB, eda and SupD from the following data: (3 marks)
Markers %
Cotransduction
CheA-eda
15
CheA- SupD
5
CheB-eda
28
CheB- SupD
2.7
eda -SupD
0

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d)
In a transformation experiment, donor DNA from an a+ b+ strain was used to

transform a recipient strain of genotype a b. The transformed classes were isolated

and their frequencies determined to be as follows:
Genetic composition
Number of individuals
a+ b+
307
a+ b
215
a b+
278

What is the frequency with which the b locus is cotransformed with the a locus?

(3 Marks)

e)
The following two-factor crosses were made to analyse the genetic linkage

between four genes in phage ? : c ,mi, s, co.
Parents
Progeny

C + X + mi
1,213 c +,1205+ mi,84++75 c mi
c + X + Si
566 c+,808+s,19++,20cs
co + X + mi
5,162 co +,6510 + mi,311++, 341 co mi
Mi + X +S
502mi +,647+ s,65++,56mi s

Construct a genetic map for the four genes

(4 Marks)
2.
Distinguish between the two methods used in mapping genes in haploid eukaryotes. What

are the relative merits of these approaches?
3.
Describe one classical experimental proof for the view that recombination involves a

physical exchange of chromosomal material.

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SECTION B (30 MARKS) Answer all the four questions
4.
In a certain primrose variety, slate-coloured flower (s) is recessive to blue flower (S), red

stigma (r) is recessive to green stigma (R), and long style (l) is recessive to short style

(L). The F 1 of a cross between true-breeding strains, were crossed to plants that had slate-

coloured flowers, red stigma and short style. The following F2 progeny were obtained:
Phenotype
Number of progeny
Slate flower, green stigma, short style 54
Slate flower, red stigma, short style
170
Blue flower, red stigma, short style
804
Slate flower, red stigma, long style
1954
Slate flower, green stigma, long style 854
Blue flower, green stigma, long style
190
Blue flower, green stigma, short style 1920
Blue flower, red stigma, long style
54

a)
Illustrate the two crosses described above

(2 Marks)
b)
Name the cross that gave rise to the segregation data observed. What is the

significance of this cross?

(1 Mark)
c)
Classify each of the F2 phenotypes and explain in genetic terms how

each one of them was obtained.

(2 Marks)
d)
What do you deduce about the relative locations of the three genes? Explain.

(1 Mark)
e)
If appropriate, make a map of these genes, showing gene order, and the distances

between the genes

(3 marks)
f)
Derive the coefficient of coincidence for interference between these genes

(1 mark)
5.
Explain the principles underlying the following gene mapping techniques:

(21/2Marks
each)
a)
Fluorescent in situ Hybridisation

b)
Somatic hybridisation
c)
Restriction
mapping

d)
Pedigree analysis
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