Botany

Define autopolyploidy. briefly describe the methods of production of autodolyploids and their importance and limitations in crop improve- ment.

What are the common aneuploid analyses for locating genes on a particular chromosome? Give abrief description of these techniques using suitable diagrams where necessary.

Define heteroploidy. List the various types of changes ni chromosome number. Briefly describe the modes of origin of aneuploids and their applications in crop improvement.

Discuss the physiological bases of heterosis.

Write short notes on the following: (i) sickle cell anaemia, (ii) pab locus in Neurospora, (ili) ma gene in maize, (iv) Adh alleles in maize, (v) inbreeding depression, and (vi) hybrid vigour.

Explain the dominance and overdominance hypotheses of heterosis giving their muin features, objections and answers to the objections. Which of the above two hypotheses is more widely accepted and why ?

Define heterosis. List its characteristic features, applications and achievements in crop improvement.

What are the man features of inbreeding depressipn? Briefly describe the degrees of inhreeding depression encountered in crop species.

Diffetentiate between the following ; (i) homozygous and homogeneous lines, (it) homozygous and heterozygous balance, (iji) genetic coad and gene pool, (iv) heterosis and luxuriance, (v) heterosis and hybrid vigour, (vi) dominance and overdominance.

Define inbreeding depression and hybrid vigour. How do these phenomena atfect the self. and cross-pollinated species? Explain with the help of suitable examples.