Just Meiosis 2018

11.4 Meiosis homologous - chromosomes in which one set comes from the male parent and the other from the female parent. match up based on size, gene location, and centromere position

SISTER CHROMATIDS ARE DIFFERENT THAN HOMOLOGOUS CHROMOSOMES!

diploid cell - contains two complete sets of chromosomes; one from each parent. Most of cells in the body are diploid.

Haploid cell - contains half the number of chromosomes (n) as a diploid (2n) cell The gametes of sexually reproducing organisms are haploid. gametes – egg and sperm

n - Used to represent the number of chromosomes in a gamete; haploid 2n - n chromosomes from female parent and n chromosomes from the male parent; diploid

For the fruit fly, diploid number is 8; 2N = 8, For gametes, Diploid Cells For the fruit fly, diploid number is 8; 2N = 8, For gametes, haploid number is 4, N = 4.

meiosis - process in reproductive cells which lead to one diploid (2n) cell producing 4 haploid (n) cells that are not genetically identical.

The number of chromosomes is reduced because the number of chromosomes per cell are cut in half through the separation of homologous chromosomes.

Fertilization - Process by which haploid gametes combine, forming a diploid cell with 2n chromosomes

Meiosis Reduces the genetic material by half Why is this necessary? from mother from father child too much! meiosis reduces genetic content

Meiosis 1 interphase 2 cell divisions: Meiosis I consists of : prophase I, metaphase I, anaphase I, telophase I, cytokinesis Meiosis II consists of: prophase II, metaphase II, anaphase II, telophase II, cytokinesis

Before Meiosis I interphase I cell undergoes a round of chromosome replication and cell prep for division

Chapter 10 Sexual Reproduction and Genetics 10.1 Meiosis Meiosis I PROPHASE I, replicated chromosomes pair with corresponding homologous chromosomes.

tetrad - structure in prophase I when containing duplicated homologous chromosomes are paired; results in four chromatids

crossing-over - process in which homologous chromosomes exchange portions of their chromatids during meiosis; only occurs during prophase I

metaphase I- paired chromosomes line up across the center of the cell. (Notice because of crossing over in prophase I, the homologous pairs are a little different than when they first paired)

anaphase I chromosome pairs separate and move toward opposite ends of the cell.

telophase I, nuclear membrane forms around each cluster of chromosomes. NOTICE THEY ARE NO LONGER PAIRED

Cytokinesis then forms two new cells.

Meiosis II –neither of the two cells undergo chromosome replication. Two cells from meiosis one will divide Result will be 4 cells

prophase II chromosomes become visible. NOT HOMOLOGOUS CHROMOSOMES; NOT SISTER CHROMATIDS

metaphase II, chromosomes line up in the center of each cell.

the paired chromatids separate in both cells. Anaphase II the paired chromatids separate in both cells.

Telophase II, and Cytokinesis Each of the four daughter cells produced in meiosis II receives separated chromatids.

The final four phases of meiosis II result in four haploid daughter cells.

The haploid cells produced by meiosis II are gametes. Gametes to Zygotes The haploid cells produced by meiosis II are gametes. In male animals, these gametes are called sperm. The female gamete is called an egg in animals.

zygote - fertilized egg results in the diploid number restored.

In mitosis, when the two sets of genetic material separate, each daughter cell receives one complete set of chromosomes.

Mitosis Meiosis Number of cell divisions Replication time   Mitosis Meiosis Number of cell divisions Replication time Sister chromatids Homologous chromosomes Synapsis/Crossing over Number of chromosomes as a result No. of Daughter cells Occurs in what kinds of cells Purpose 2 1 1 in interphase 1 in interphase yes Yes only in interphase I no Yes, prophase I, Metaphase I, telophase I no Yes, prophase I only Diploid 2n Haploid n 2 4 Body cells Sex cells Growth/repair in body cells Produce gametes