Meiosis Gamete Production

Meiosis Similar in many ways to mitosis Several differences however Involves 2 cell divisions Results in 4 cells with 1/2 the normal genetic information. Vocabulary: Diploid (2N) - Normal amount of genetic material Haploid (N) - 1/2 the genetic material. Meiosis results in the formation of haploid cells. In Humans, these are the Ova (egg) and sperm. Ova are produced in the ovaries in females Process is called oogenesis Sperm are produced in the testes of males. Process is called spermatogenesis Meiosis occurs in 2 phases: Meiosis 1 & Meiosis 2

Spermatogenesis & Oogenesis

REMEMBER: I P1 M1 A1 T1 P2 M2 A2 T2 C

MEIOSIS AND MITOSIS ARE THE SAME EXCEPT FOR: PROPHASE I ANAPHASE I

Prophase 1 – CROSSING-OVER Segments of homologous chromosomes break and reform at similar locations. Results in new genetic combinations of offspring. This is the main advantage of sexual reproduction

Anaphase 1 During anaphase 1, each homologous chromosome is pulled to opposite sides of the cell. Unlike mitosis, THE CENTROMERES DO NOT BREAK.

Meiosis II – Follow the same steps as MITOSIS DNA does not double Chromosomes randomly line-up along middle like regular mitosis. During anaphase 2, CENTROMERES BREAK and each chromosome is pulled to opposite sides of the cell. Nuclei reform and cytokenesis occurs

Meiosis Prophase I Metaphase I Anaphase I Telophase I

Overview of Meiosis

Meiosis B-4.5 Summarize the characteristics of the phases of meiosis I and II. Taxonomy Level: 2.4-B Understand Conceptual Knowledge

Key Concepts Daughter cells: diploid; haploid, gamete, zygote Meiosis I: interphase, prophase I, tetrad, crossing over; metaphase I; anaphase I; telophase I, cytokinesis Meiosis II: prophase II, metaphase II, anaphase II, telophase II

Meiosis meiosis is important to sexual reproduction mitosis is important to asexual reproduction In order for the offspring produced from sexual reproduction to have cells that are diploid (containing two sets of chromosomes, one set from each parent), the egg and sperm cells must be haploid (contain only one of each type of chromosome). The division resulting in a reduction in chromosome number is called meiosis.

Meiosis occurs in two steps: Meiosis I, in which the chromosome pairs replicate, results in two haploid daughter cells with duplicated chromosomes different from the sets in the original diploid cell. Meiosis II, in which the haploid daughter cells from Meiosis I divide, results in four haploid daughter cells called gametes, or sex cells (eggs and sperm), with undoubled chromosomes. Tetrad The four haploid cells formed at the end of meiosis. The term was formerly used for the four chromatids making up a chromosome-pair at the first division of meiosis.

Meiosis I