LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034.
B. Sc. DEGREE EXAMINATION - Plant Biology and Biotechnology
SUPPLEMENTARY EXAMINATION – JUNE 2007
Date: 26.06.07
Max: 100 Marks
Time:9.00 – 12.00
PB5506 – GENETICS AND PLANT BREEDING
Part A
(20 marks)
Answer All questions
I Choose the Correct Answer
( 5 x 1 = 5 marks)
01. If plant heterozygous for tallness is selfed, the F2 generation has both tall and dwarf
plants. This proves the principle of
a. dominance
b. segregation
c. incomplete dominance
d. independent assortment
02. Building blocks of the nucleic acid are
a. nucleotides
b. nucleosides
c. aminoacid
d. nucleoproteins.
03. Neurospora is suitable for genetic studies because
a. its vegetative phase is diploid
b. it has long life cycle and it can be cultured in all media
c. it can be cultured in defined media in the laboratory and it has very short life
cycle
d. it can be cultured in defined media in the laboratory and it has very long life
Cycle.
04. Which of the following enzymes is required for most transposition events.
a. DNA polymerase
b. Telomerase
c. Reverse transcriptase
d. Transposase
05. The “ Use and Disuse “ principle of evolution was proposed by
a. Hugo de vries
b. Lamarck c. Weismann
d. Darwin
II State whether the following statements are True or False
(5 x 1 = 5 marks)
06. In the F2 generation, phenotypic and genotypic ratio are identical in cases of
incomplete dominance.
07. In the operon model, the regulator gene regulates chemical reactions in the cell by
inactivating enzymes.
08. Genes are located on the chromosome in a linear manner.
09. Transition mutations substitute one purine for a pyrimidine.
10. Lamarck was the first scientist who propounded the theory of evolution.
III. Complete the following
( 5 x 1 = 5 marks)
11. _____________ are alternate forms of a gene having the same locus in homologous
chromosome.
12. DNA replication on the ________ strand needs only one RNA primer.
13. The process by which the DNA of the nucleus passes information to RNA is called
_____________.
14. _____________ is an artificial polyploid formed by hybridization of different species.
15. The famous book “ Origin of species” was written by _____________.
-2IV. Answer all, each in about 50 words
16. What are lethal genes?
17. Define nucleoid.
18. What are group II introns?
19. Write notes on frame shift mutation.
20. What is heterosis?
( 5 x 1 = 5 marks)
PART B
( 5 x 8 = 40 marks)
Answer any five, each within 350 words only. Draw diagrams and flowcharts wherever
necessary.
21. Describe Dihybrid cross with suitable example.
22. Give an account of the cytoplasmic inheritance of plastids in plants.
23. Write notes on negative and positive supercoiling.
24. List out the characteristics of genetic code.
25. With suitable example explain duplication and inversion.
26. What is genetic recombination? Explain genetic recombination using Neurospora
tetrad formation.
27. Mention the objectives and importance of plant breeding.
28. Briefly explain the principles of Natural selection.
PART C
( 2 x 20 = 40 marks)
Answer the following, each within 1500 words only. Draw diagrams and flowcharts
wherever necessary.
29 a. Give a detailed account on the structure of DNA.
OR
b. Explain the various events involved in semiconservative method of replication.
30 a. Describe the transcriptional and post translational regulation of gene expression.
OR
b. Describe the following:
i. Down’s syndrome (5)
ii. Recombinational and SOS repair mechanisms(10).
iii. Post transcriptional modification(5).
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