BIOL2165: Genetics-IITutorial 2

1. What do you understand by the term translocation? Describe briefly the cytological and genetic effects of translocation on plants. Discuss the evolutionary significance of translocations, with appropriate examples.

2. a) Define the terms 'allopolyploidy' and 'diplodization'.

b) Briefly discuss the role of allopolyploidy in the evolution of plant species. Illustrate your answer with a named example.

c) The New World cotton species Gossypium hirsutum has a 2n chromosome number of 52. The Old World species, G. thurberi and G. herbaceum each have a 2n number of 26. Hybrids between these species show the following chromosome pairing arrangements at meiosis.

Hybrid Pairing arrangement____________________________________________________________G. hirsutum x G. thurberi 13 small bivalents and 13 large univalents

G. hirsutum x G. herbaceum 13 large bivalents and 13 small univalents

G. thurberi x G. herbaceum 13 large univalents and 13 small univalents.________________________________________________________________Interpret these results and clearly indicate the phylogenetic relationships among the species. How would you go about proving that your interpretation is correct?

d) How many chromosomes would be found in somatic cells of an allotetraploid derived from two plants, one with n = 7 and the other with n = 10?

3. Which types of chromosomal aberration:a. increase the amount of genetic material in a particular chromosomeb. increase the amount of genetic material in all chromosomesc. decrease the amount of genetic material in a particular chromosome d. change the position of DNA sequences in a single chromosome without changing the amount of genetic

materiale. move DNA from one chromosome to a non-homologous chromosome

4. a) How can one diagnose genetic deletions?

b) How does a deletion cause pseudodominance?