1. Somatic (body) cells reproduce by mitosis
Somatic (body) cells reproduce by mitosis. Gametes are produced by the process of meiosis. Compared to the parent cells, how many chromosomes are found in gametes? A. One-fourth the number of chromosomes B. The same number of chromosomes C. Twice the number of chromosomes D. Half the number of chromosomes

2. MEIOSIS
SC.912.L.16.16Describe the process of meiosis, including independent assortment and crossing over. Explain how reduction division results in the formation of haploid gametes or spores.

3. Interactive Notebook Right Page: Meiosis graphic organizer
Left Page: Meiosis Poker
Right Page: Meiosis graphic organizer

4. What is meiosis?
Meiosis is a two-part cell division process in organisms that sexually reproduce.
Meiosis makes haploid cells (the cell only has one copy of each chromosome.) from diploid cells (the cell has two copies of each chromosome).

5. Before meiosis begins, the DNA undergoes replication
Before meiosis begins, the DNA undergoes replication.  When you first see chromosomes in meiosis I, they have sister chromatids. 

6. Prophase I
DNA condensation occurs, the nuclear envelope and nucleoli disappear, and the spindle starts to form. As DNA condensation proceeds and the chromosomes first become visible, they are visible as tetrads (groups of four).

7. Prophase I continued
Also during prophase 1 crossing over (the physical exchange of chromosome parts) occurs. Crossing-over is the process that can give rise to genetic recombination.

8. Metaphase I
Tetrads line up at the equator. The spindle has completely formed. Independent assortment is occurring.

9. Metaphase I continued
Independent assortment refers to the random arrangement of pairs of chromosomes. The diagram below shows four possible arrangements of chromosomes during metaphase 1 from an individual that has 6 total chromosomes.
Suppose that the pink chromosomes are those that the individual inherited from its mother and the blue colored ones were inherited from its father. For each chromosome pair, the chromosome that is on the left (maternal or paternal) is determined randomly. As can be seen, there are several alignment possibilities.

10. Anaphase I
Tetrads pull apart and chromosomes with two chromatids move toward the poles.

11. Telophase I
Chromosomes with two chromatids decondense and a nuclear envelope reforms around them. Each nucleus is now haploid. Keep in mind that it is not the number of chromatids per chromosome that determine whether a cell is diploid or haploid, but, it is the number of chromosomes and whether they are paired that determines this.

12. Prophase II
Chromosomes with two chromatids become visible as they condense (and the nuclear envelope and nucleoli disappear, and the spindle is forming).

13. Metaphase II
Chromosomes with two chromatids line up at the equator. The spindle is fully formed. Although genetic recombination primarily occurs during meiosis I, the way the chromosomes line up during metaphase II can also help to make unique daughter cells.

14. Anaphase II
    Chromosomes split, so that a chromosome with only one chromatid heads toward each pole.

15. Telophase II
Chromosomes with only one chromatid decondense and get surrounded by new nuclear envelopes.  The four daughter cells are now all haploid and have the right amount of DNA.  They are ready to develop into sperm or eggs now.

16. Somatic (body) cells reproduce by mitosis
Somatic (body) cells reproduce by mitosis. Gametes are produced by the process of meiosis. Compared to the parent cells, how many chromosomes are found in gametes? A. One-fourth the number of chromosomes B. The same number of chromosomes C. Twice the number of chromosomes * D. Half the number of chromosomes

17. SC.912.L Assessment
The diagram shows two homologous chromosomes before and after meiosis occurred. What process caused the arms of the chromosomes to be in different places after meiosis?
A. Sex linkage
B. Codominance
C. Crossing over
D. Independent assortment
Answer: C

18. Some species have greater genetic diversity than other species
Some species have greater genetic diversity than other species. Which of the following statements explains why some species have greater genetic diversity?
Sexual reproduction results in multiple genetic combinations found in the diploid cells of a single offspring.
The simplicity of asexually reproducing species results in a greater production of offspring and genetic information.
Meiosis involved crossing over, resulting in greater variation of genetic information in spores and gametes in these species.
Mitosis produces complex haploid spores or gametes that combine to contain double the genetic information in these species.
Answer: C

19. Sperm cells of the Russian dwarf hamster, Phodopus sungorus, contain 14 chromosomes. What is the total number of chromosomes that would be contained in a normal, newly formed zygote of this species?
A. 7
B. 14
C. 28
D. 42
Answer: C