1. Figure 1

2.  1-Mitosis  2-Meiosis

3.  Mitosis is a kind of cell divison which occurs in somatic cells and results in two daughter cells.  These daughter cells are identical to each other and to the parent cell.  Daughter cells are diploid which means that they they have 2 sets of chromosomes.  One set of chromosomes is donated from the mother and the other set of chromosome donated from father.

4.  1-Interphase  2-Prophase  3-Metaphase  4-Anaphase  5-Telophase Figure 2

5.  There are 3 stages in interphase;  -G1: The cells grow and get bigger for the division.  -S : DNA is synthesized by the process of DNA Replication.  -G2 : Mitochondria and other organelles divide. Figure 3

6.  Chromosomes become shorter and fatter.  They move to opposite poles of the cell and spindle fibres are formed.  Nucleolus disappears.  Nuclear membrane breaks down Figure 4

7.  Chromosomes line up at the equator individually.  Spindle fibers attach to chromosomes at the centromere. Figure 5

8.  Spindle fibres pull chromosomes apart.  Microtubules shortening.  Centromere of each chromosomes breaks down.  Daughter chromosomes travels to opposite poles. Figure 6

9.  All chromosomes are at opposite poles.  Spindle fibres break down.  Nuclear envelope reformed.  Chromosomes become invisible. Figure 7

11.  Meiosis is a kind of cell division which occurs in gametes(sperms and eggs) and results in four daughter cells.  Daughter cells are genetically different from each other and from parent cells.  Daughter cells are haploid which means that they have one complete set of chromosomes.  During meiosis DNA replicates once but the nucleus divides twice. Therefore two division occur in meiosis.

12.  It halves the chromosome number.  It is important to have a diploid cell with correct number of chromosome(46 chromosome).  It increases variation.

13.  Prophase 1  Metaphase 1  Anaphase 1  Telophase 1

14.  Most of the steps are same as in the mitosis except;  Homologous chromosomes pair up to from bivalent consisting of 4 chromatids.  Two chromosomes can overlap with each other which is known as CROSSING OVER.

15.  Most of the steps are same as mitosis except;  Spindle fibres move bivalent chromosomes to line up at the equator instead of single chromosomes.

16.  The centromeres do not divide  One chromosome from each homologous pair moves to each end of the cell.  As a result, the chromosome number in each cell is half of the original.

17.  All of the steps are same as mitosis except;  Whole chromosome is produced instead of one sister chromatid.

18.  The second division of meiosis is completely the same as mitosis.  However at the end of Meiosis, 4 daughter cells each with half of the chromosome number of the original diploid cell are formed.

19. Prophase 2 Metaphase 2Anaphase 2 Telophase 2

21.  5 differences between mitosis and meiosis MITOSISMEIOSIS 2 daughter cells formed4 daughter cells formed Occurs in body cellsOccurs in gametes Daughter cells are diploidDaughter cells are haploid Daughter cells are identical to each other Daughter cells are different from each other No crossing over of chromosomes Crossing over of chromosomes in prophase 1

22. (a) (i) The diagrams show some of the stages of mitosis. Arrange the letters A - D to give the correct sequence of stages. Sequence D A C B

23. (ii)Describe the role of the spindle in mitosis: (b)Sexual reproduction involves the fusion of gametes. Explain the importance of meiosis in the life cycle of a sexually reproducing organism. It attaches centromeres and seperates the daughter chromatids. Meiosis halves the chromosome number and increase the variation.

24.  Edexcel AS Biology, A Pearson Company, 2008, page 148,149,150,158,159  Richard Llopis Garcia’s CD