Meiosis and Nondisjunction

Meiosis Definition: Cell division that divides the number of chromosomes per cell in half to produce sperm and eggs

Diploid vs. Haploid Diploid Contains two sets of chromosomes (one set from the mom and one set from the dad) Haploid One set of chromosomes

Stages of Meiosis Meiosis I Prophase I Metaphase I Anaphase I Telophase I Meiosis II Prophase II Metaphase II Anaphase II Telophase II

Meiosis I

Prophase I Each chromosome pairs with its corresponding homologous chromosome to form a tetrad Crossing over (exchange of information between homologous chromosomes) takes place

Prophase I

Metaphase I Homologous chromosomes pair together and line up down the middle of the cell

Metaphase I

Anaphase I The homologous chromosomes are pulled APART to opposite ends of the cell

Anaphase I

Telophase I and Cytokinesis Nuclear membranes form The cell separates into two cells

Telophase I and Cytokinesis

Meiosis II

Prophase II

Metaphase II

Anaphase II

Telophase II and Cytokinesis

Nondisjunction Definition: When gametes have an abnormal number of chromosomes When this occurs: Meiosis

Chromosomal Disorders due to Nondisjunction 1) Down Syndrome 2) Klinefelter's Syndrome 3) Turner's Syndrome

Down Syndrome "Trisomy 21" Characteristics:

Klinefelter's Syndrome Characteristics:

Turner's Syndrome Characteristics: