Learning Targets“I Can…”

• Contrast mitosis and meiosis.

• Identify the process that creates gametes (sex cells).

MITOSIS MEIOSIS

Learning Targets“I Can. . .”

-Define “gamete.”

-Distinguish between haploid (N) and diploid (2N) cells.

-Calculate the haploid (N) number of chromosomes given the diploid (2N) number, and vice versa.

-Explain why gametes are haploid.

-Describe the major events of meiosis.

-Define a “tetrad.”

Meiosis

The Creation of

Gametes

Definition

Cell division to form gametes (sex cells), which have half the chromosome number of the original cell

Stages of Meiosis

1. Interphase: DNA replicates (just like mitosis)

Stages of Meiosis

2. Prophase I

a. Nucleus disappears

b. Replicated DNA condenses into chromosomes

c. Homologous chromosomes pair to form tetrads

Stages of Meiosis

3. Metaphase I

Stages of Meiosis

4. Continues through Anaphase I and Telophase I. By Prophase II . . .

Stages of Meiosis

5. Metaphase II

Stages of Meiosis

6. Continues though Anaphase II and Telophase II

Stages of Meiosis

7. The four final cells are gametes, either sperm cells or egg cells

8. The gametes are different from the original cell because they only have half the number of chromosomes

Why are 4 daughter cells different from the original parent cell?

Why are 4 daughter cells different from the original parent cell?1. Gametes are haploid.

a. One copy of each chromosome

b. Haploid cells are designated as N.

2. All other cells are diploid.

a. Two copies of each chromosome.

b. Diploid cells are designated as 2N.

Why are 4 daughter cells different from the original parent cell?

3. Offspring have homologous chromosomes (one set from mom and one set from dad)

4. Each homologous pair has two alleles

a. Alleles: alternative forms of genes

-Dominant (A)

-Recessive (a)

b. These alleles get shuffled around between homologous chromosomes during prophase 1 when they are paired in tetrads

References

• http://www.exoticreps.co.uk/mitosis-meiosis.jpg

• http://labspace.open.ac.uk/file.php/2668/SK195_1_008i.jpg

• http://homepage1.nifty.com/scilla/sonota/ityou/meiosis.jpg

• http://study.com/academy/lesson/alternation-of-generations-the-gametophyte-and-sporophyte.html