IGNOU LSE-03 - Genetics

1. Describe with appropriate examples the role of environment in the determination of sex. 2. Detail the Watson and Crick model of DNA structure. How did it fit in the data provided by Chargaff? 3. Does the operon concept apply to eukaryotes? Describe a suggested mechanism for gene regulation in eukaryotes. 4. In a randomly mating laboratory population of Drosophila, 4 per cent of the flies have black bodies (black is autosomal recessive, b) and 96 per cent have brown bodies (normal colour, B). If this population is assumed to be in Hardy-Weinberg equilibrium, what are the allelic frequencies of B and b, and the genotypic frequencies of BB and Bb? 5. Detail the molecular basis of mutations. 6. Enlist the different types of lymphocytes. Mention their function, site of differentiation, and the type of immunity imparted by them. 7. Describe any two modern methods for the improvement of crop plants. 8. In peas, Tall (T) is dominant over dwarf (t), Yellow is dominant over green (y), and Smooth (S) is dominant over wrinkled (s). What fraction of the offspring in the following cross would be homozygous recessive for all gene pairs in the cross: YyTtss X YyttSs? 9. (a) How linkage maps are constructed? What is their use in genetic studies? (b) How many linkage groups would be revealed by an analysis of human genome? Choose the correct answer amongst the choices given below: i) 2 ii) 13 iii) 23 iv) 46 (c) Determine the order of genes along a chromosome based on the following recombination frequencies: A - B 8 map units A - C 28 map units A - D 25 map units B - C 20 map units B - D 33 map units 10. Differentiate between the following pairs: i) Somatic and gametic mutations ii) Structural and regulatory genes iii) Euchromatin and heterochromatin iv) Cell-mediated and humoral immunity v) Lytic and Iysogenic cycles

1. Write short notes on the following:  (i) Segregation Law of Mendel (ii) Hardy Weinberg's law (iii) X -linked traits in humans (iv) Epistasis  2. (a) What are multiple alleles? Explain giving a suitable example. (b) Describe packaging of DNA into chromosome.  3. Differentiate between the following:  (i) Phenotype and genotype (ii) DNA and RNA (iii) Deamination and Depurination (iv) T and B lymphocytes 4. What are autosomal and sex chromosome aneuploidies? Describe few of those found in humans.  5. a) Describe Hershey and Chase experiment that proved that DNA is the hereditary material. b) Explain lytic cycle of a bacteriophage.  6. (a) Explain Chargaff’s rule. (b) Define mutagenesis. What are major agents leading to mutagenesis?  7. Explain the model for regulation of the lac operon with the help of a well labelled diagram.  8. Describe in brief the following:  (i) Chemical mutagens (ii) ABO Blood group system (iii) Autoimmune diseases (iv) Genetic counselling 9. (a) Describe Griffith’s experiment to show transformation in DNA. (b) Genetic engineering can be used for improving nutritional value of food. Explain in detail. 10. Describe the various applications of genetic engineering.