1. Describe the structure of ribosomes. (5 marks) 2. Explain any FIVE Features of Thylakoid System. (5 marks) 3. Using any FIVE-features, differentiate between Euchromatin and Heterochromatin. (5 marks) 4. With aid of a well labeled diagram explain the FOUR phases of the cell cycle. (5 marks) 5. Describe the components of mammallan connective tissue. (5 marks) 6. Classify meristems on the basis of origin and position in the plant body into ANY FIVE categories. (5 marks) 7. Describe the structure of an ovule. (5 marks) 8. List any FIVE functions of sertoli cells in spermatogenesis. (5 marks) 9. Explain the formation of the primitive streak and mesoderm during gastrulation in heavily telolecithal egg of chick. (5 marks) 10. Identify ANY FIVE significance of mitosis. (5 marks) 11.Using ANY FIVE features differentiate between mitosis and meiosis. (5 marks) 12.With aid of a well labeled diagram illustrate ANY FOUR Extra embryonic membranes of mammals. (5 marks) 13.With aid of a well labeled diagram describe embryo sac development tin Anglosperms. (5 marks) 14.Describe stages involved in oogenesis. (5 marks) 15. Explain how fast block to poly-spermy is achieved as means of prevention of polyspermy. (5 marks)

1. Ribosomes are composed of ribosomal RNA and proteins, and they are divided into two subunits, large and small, which come together during protein synthesis.<br />2. The thylakoid system consists of thylakoids, granum, stroma, pigment, and ATP. These components work together to capture light energy and convert it into chemical energy.<br />3uchromatin is less condensed, gene-rich, and transcriptionally active, while heterochromatin is more condensed, gene-poor, and transcriptionally inactive.<br />4. The cell cycle includes the phases G1, S, G2, and M. These phases involve cell growth, DNA replication, preparation for mitosis, and mitosis itself.<br />5. Mammalian connective tissue consists of cells, fibers, and extracellular matrix. These components provide support, protection, and integration to the body's tissues.<br />6. Meristems can be classified into apical meristem, lateral meristem, intercalary meristem, protoderm, and procambium based on their origin and position in the plant body.<br />7. An ovule consists of the nucellus, integuments, and micropyle. These structures are involved in the development and protection of the egg cell.<br />8. Sertoli cells provide nutrients, regulate the environment, produce testicular fluid, form the blood-testis barrier, and promote spermatogenesis.<br />9. The primitive streak forms during gastrulation in heavily telolecithal eggs of chicks, leading to the development of the mesoderm.<br />10. Mitosis is significant for growth, tissue repair, asexual reproduction, genetic consistency, and cellular specialization.<br />11. Mitosis involves one division and produces two identical daughter cells, while meiosis involves two divisions and produces four genetically different daughter cells.<br />12. The extraembryonic membranes of mammals include the amnion, yolk sac, allantois, and chorion. These membranes provide protection, nutrition, waste removal, and gas exchange.<br />13. Embryo sac development in angiosperms involves the formation of the megaspore, megagametophyte, and embryo sac, which are essential for fertilization and seed formation.<br />14. Oogenesis involves the stages of oogonium, primary oocyte, secondary oocyte, and mature ovum, leading to the production of a mature egg cell.<br />15. The fast block to polyspermy is achieved through the cortical reaction, where cortical granules release their contents into the perivitelline space, modifying the zona pellucida to prevent additional sperm from binding and penetrating.