1. Chromosomes and Mieosis

3. Chromosome and Cell types
Two main types of cells
Body cells
Also known as somatic cells (all cells in our body except sperm or eggs)
Divide to make more by MITOSIS
Sex cells
Also known as gamete cells (sperm and eggs)
Divide to make more by MEIOSIS

4. Chromosome and Cell types
In humans, somatic cells have 23 pairs of chromosomes, meaning they have 46 total chromosomes.
Somatic cells are DIPLOID cells (they have a full set of chromosomes)

5. In Mitosis, the daughter cells contain the same number of chromosomes as the parent cell

6. Chromosome and Cell types
Gamete cells only have 1 of each chromosome
23 chromosomes
Because sex cells only have HALF the number of chromosomes, they are called HAPLOID cells

9. Haploid and Diploid
If a diploid cell had 20 chromosomes, how many chromosomes would be in the haploid cell?______
If a haploid cell had 12 chromosomes, how many chromosomes would be in a diploid cell?______
A muscle cell has 30 chromosomes. After mitosis, how many chromosomes do its daughter cells have?______
A cell has 22 chromosomes. After meiosis, how many chromosomes would it have?______
A muscle cell has 44 chromosomes. How many chromosomes would the sex cells have?______

10. Creating Cells for Sexual Reproduction
Meiosis:
Creating Cells for
Sexual Reproduction

11. Meiosis Meiosis is the process by which sex cells are produced
Similar to mitosis, however it includes TWO cell divisions resulting in 4 daughter cells with half the number of chromosomes.

12. MEIOSIS I: Homologous chromosomes separate
MEIOSIS I: Homologous chromosomes separate
INTERPHASE
PROPHASE I
METAPHASE I
ANAPHASE I
Centrosomes
(with centriole
pairs)
Microtubules
attached to
kinetochore
Metaphase
plate
Sister chromatids
remain attached
Sites of crossing over
Spindle
Figure 8.14 The stages of meiosis.
Nuclear
envelope
Sister
chromatids
Tetrad
Centromere
(with kinetochore)
Homologous
chromosomes separate
Chromatin

13. MEIOSIS II: Sister chromatids separate
MEIOSIS II: Sister chromatids separate
TELOPHASE II
AND CYTOKINESIS
TELOPHASE II
AND CYTOKINESIS
PROPHASE I
METAPHASE II
ANAPHASE II
Cleavage
furrow
Sister chromatids
separate
Haploid daughter
cells forming
Figure 8.14 The stages of meiosis.

14. Prophase I Chromosomes are already copied Centrioles separate
Nuclear membrane breaks down

15. Metaphase I
Chromosome pairs line up next to each other

16. Anaphase I
Chromosome pairs split
Sister chromatids stay connected

17. Telophase I Cell starts to divide in two
Nuclear membranes start to form again

18. Prophase II Cells have one set of sister chromatids
Nuclear membrane breaks down
Centrioles separate

19. Metaphase II
Sister chromatids line up at the middle of the cell

20. Anaphase II
Sister chromatids divide

21. Telophase II Cells start to split in two
Each cell has one set of chromosomes—it is a haploid

22. Replicated chromosome
Fig. 13-9a
MITOSIS
MEIOSIS
MEIOSIS I
Parent cell
Chiasma
Chromosome
replication
Chromosome
replication
Prophase
Prophase I
Homologous
chromosome
pair
2n = 6
Replicated chromosome
Metaphase
Metaphase I
Anaphase
Telophase
Anaphase I
Figure 13.9 A comparison of mitosis and meiosis in diploid cells
Telophase I
Haploid
n = 3
Daughter
cells of
meiosis I 2n 2n
MEIOSIS II
Daughter cells
of mitosis n n n n
Daughter cells of meiosis II 22