Section 4: Meiosis
Chromosome Number
All organisms have different numbers of chromosomes. A body cell in an adult fruit fly has 8 chromosomes: 4 from the male parent and 4 from its female parent.
Homologous - each chromosome that came from the male parent has a
corresponding chromosome from the female parent.
Haploid and Diploid Cells
A cell that contains both sets of homologous chromosomes is said to be diploid
This is sometimes represented by the symbol 2N . For the fruit fly, it would be written like this: 2N = 8.
When a cell only has a single set of chromosomes, the cell is considered haploid
This is sometimes represented by the symbol N.
Gametes- specialized cell involved in sexual reproduction. Only contains half the necessary genetic material. (Sex cells such as sperm and eggs.)
Humans have 46 chromosomes in a diploid cell. 23 in a haploid cell.
The Process of Meiosis
Meiosis is a process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.
Meiosis is divided into two parts Meiosis I and Meiosis II.
Label each part of Meiosis I
Interphase I Prophase I Metaphase I Anaphase I Telophase I and Cytokinesis

Label each part of Meiosis II
Interphase II Prophase II Metaphase II Anaphase II Telophase II & Cytokinesis
Prophase I : Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.
There are 4 chromatids in a tetrad.
Homologous chromosomes can exchange portions of their chromatids in a process called crossing over . This allows for different combinations of genes.
Comparing Mitosis and Meiosis
Metaphase I, Anaphase I, and Telophase I are all the same as in mitosis.
The goal of mitosis is to create two identical daughter cells. Meiosis results in four haploid (N) genetically different daughter cells.
Differences in Meiosis
The female sex cell is called egg and the process is called oogenesis.
The male sex cell is called sperm and the process is called spermatogenesis.
In both cases, meiosis begins with one cell that divides. In oogenesis, only 1 viable
(living) egg is produced and the remaining 3 are called polar bodies .
In spermatogenesis, 4 viable sperm are produced.

Draw the flow chart for Oogenesis.
Draw the flow chart for Spermatogenesis.