GPB 614 Advances in Cytogenetics Question Paper

 Department of Genetics and Plant Breeding, CoA, GKVK, Bengaluru

First Exam
Advances in Cytogenetics (GPB 614) (2+0)
Marks: 20.0

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I. Answer the following

1. Describe in detail the structure and chemical constituents of chromosome. – 2.0

2. Explain the cytological basis of crossing over. – 1.0

3. Illustrate only with diagram Metaphase of mitosis, Metaphase I, Metaphase II, Anaphase I, II and Telophase I and II (2n=4). – 1.0

4. Translocation heterozygotes have reduced fertility because of unbalanced products of meiosis that come from adjacent segregations. Illustrate this for the following:
   N1=AB.CDEFG, N2=MN.OPQRS
   T1=AB.CDQPQRS, T2=MN.OPEFG – 1.0

5. Discuss on permanent translocation heterozygotes in Oenothera lamarckiana. – 2.0

6. Explain with diagram the possibility to have only translocation heterozygotes? – 2.0

7. Discuss on Saccharum species: their origin, evolution, basic chromosome number and chromosome number/s in cultivated species of sugarcane. Also discuss on mobilization of cane. – 2.0

8. What are the basic and haploid chromosome numbers of Oryza sativa? What kinds of aberrations lead to changes in basic and haploid chromosome number? – 2.0

9. Describe briefly on inheritance of autotetraploids. 8.16 If two alleles, A and a, exist at a locus, a genotype combination can be illustrated in an autotetraploid: quadruplex (AAAA), triplex (AAAa), duplex (AAaa), simplex (Aaaa), nulliplex (aaaa). Explain with expected ratios. – 3.0

10. A dominant gene W+ produces yellow flowers in a certain plant species and its recessive allele w produces white flowers. Plants trisomic for the chromosome bearing the color locus will produce n and n+1 functional female gametes, but viable pollen has only the n number. Find the phenotypic ratio expected from each of the following crosses:

Seed Parent × Pollen Parent
a) ++w × ++w
b) +w × ++w
c) +w × +w
d) ++w × +w – 2.5

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II. Give reasons for the following

1. DNA synthesis of 0.33% occurs in pachytene stage of meiosis

2. Deletions are more harmful than duplications

3. Metaphase is preferred for karyotyping

4. Amount of DNA of somatic cell is constant for a particular species however it depends on stage of cell cycle

5. Allopolyploids aid in creation of new species

6. Univalent shift? What are the consequences and reasons?

7. Why the frequency of trisomics in subsequent generations is low? – 3.5