Chapter 10

Meiosis results in diploid organisms

• a.Production of gametes
• b.Reduction in the number of chromosomes
• c.Introduction of variation
• d.All of the above

At which stage of meiosis does the genetic constitution of gametes is finally decided

• a.Metaphase I
• b.Anaphase II
• c.Metaphase II
• d.Anaphase I

Meiosis occurs in organisms during

• a.Sexual reproduction
• b.Vegetative reproduction
• c.Both sexual and vegetative reproduction
• d.None of the above

During anaphase-I of meiosis

• a.Homologous chromosomes separate
• b.Non-homologous chromosomes separate
• c.Sister chromatids separate
• d.Non-sister chromatids separate

Mitosis is characterised by

• a.Reduction division
• b.Equal division
• c.Both reduction and equal division c. Both reduction and equal division
• d.Paining of homologous chromosomes

A bivalent of meiosis-I consists of

• a.Two chromatids and one centromere
• b.Two chromatids and two centromere
• c.Four chromatids and two centromere
• d.Four chromatids and four centromere

Cells which are not dividing are likely to be at

• a.G1
• b.G2
• c.Go
• d.S phase

Which of the events listed below is not observed during mitosis?

• a.Chromatin condensation
• b.Movement of centrioles to opposite poles
• c.Appearance of chromosomes with two chromatids joined together at the centromere.
• d.Crossing over

Identify the wrong statement about meiosis

• a.Pairing of homologous chromosomes
• b.Four haploid cells are formed
• c.At the end of meiosis the number of chromosomes are reduced to half
• d.Two cycle of DNA replication occurs

Select the correct statement about G1 phase

• a.Cell is metabolically inactive
• b.DNA in the cell does not replicate
• c.It is not a phase of synthesis of macromolecules
• d.Cell stops growing

At what stage of cell cycle does DNA synthesis take place?

It is said that the one cycle of cell division in human cells (eukaryotic cells) takes 24 hours. Which phase of the cycle, do you think occupies the maximum part of cell cycle?

It is observed that heart cells do not exhibit cell division. Such cells do not divide further and exit ___________ phase to enter an inactive stage called ___________ of cell cycle. Fill in the blanks.

In which phase of meiosis are the following formed? Choose the answers from hint points given below.

• a.Synaptonemal complex ____________________________
• b.Recombination nodules ____________________________
• c.Appearance/activation of ____________________________ enzyme recombinase
• d.Termination of chiasmata ____________________________ e. Interkinesis ____________________________ f. Formation of dyad of cells ____________________________ Hints : 1) Zygotene, 2) Pachytene, 3) Pachytene, 4) Diakinesis, 5) After Telophase-I /before Meosis-II, 6) Telophase-I /After Meiosis-I.

chromosomes and some with 32 chromosomes. What possible reasons could you assign to this difference in chromosome number. Do you think cells with 16 chromosomes could have arisen from cells with 32 chromosomes or vice versa? 6. The following events occur during the various phases of the cell cycle, Name the phase against each of the events.

• a.Disintegration of nuclear membrane _________________________
• b.Appearance of nucleolus _________________________
• c.Division of centromere _________________________
• d.Replication of DNA _________________________ 7. Mitosis results in producing two cells which are similar to each other. What would be the consequence if each of the following irregularities occur during mitosis? a. Nuclear membrane fails to disintegrate b. Duplication of DNA does not occur c. Centromeres do not divide d. Cytokinesis does not occur. CELL CYCLE AND CELL DIVISION 53 8. Both unicellular and multicellular organisms undergo mitosis. What are the differences, if any, observed in the process between the two? 9. Name the pathological condition when uncontrolled cell division occurs. 10. Two key events take place, during S phase in animal cells, DNA replication and duplication of centriole. In which parts of the cell do events occur? 11. Comment on the statement – Meiosis enables the conservation of specific chromosome number of each species even though the process per se, results in reduction of chromosome number. 12. Name a cell that is found arrested in diplotene stage for months and years. Comment in 2-3 lines how it completes cell cycle? 13. How does cytokinesis in plant cells differ from that in animal cells?