Meiosis Test Part Two: Steps Of Meiosis I And Meiosis II Flashcards
Meiosis
A process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
Prophase I
Each replicated chromosome pairs with its corresponding homologous chromosome
Pairing forms a structure called a tetrad, which contains 4 chromatids
As homologous chromosomes form tetrads, they undergo the process of crossing over
The chromatids of the homologous chromosomes cross over each other. The crossed sections of the chromatids are then exchanged. Produces new variations of alleles in the cell - genes
Spindle forms and attaches to each tetrad
Crossing over
The chromatids of the homologous chromosomes cross over each other. The crossed sections of the chromatids are then exchanged. Produces new variations of alleles in the cell - genes
Metaphase I
Paired homologous chromosomes line up across the center of the cell
Anaphase I
Spindle fibers pull each homologous chromosome pair toward opposite ends of the cell
SISTER CHROMOSOMES DO NOT SEPARATE
Separated chromosomes cluster at opposite ends of the cell
Telophase I and cytokinesis
A nuclear membrane forms around each cluster of chromosomes. Cytokinesis (the division of the cell’s cytoplasm) follows, forming two new cells
Meiosis I results in
Two daughter cells.
Because each pair of homologous chromosomes was separated, neither daughter cell has two complete sets of chromosomes (unlike a diploid cell)
The daughter cells have sets of chromosomes and alleles different from each other and from the diploid cell that entered meiosis I
Prophase II
The cells chromosomes - each consisting of 2 chromatids - become visible.
Chromosomes do not pair for tetrads, homologous chromosomes were already separated during meiosis I
Metaphase II
Chromosomes line up at the center of each cell
Anaphase II
Paired chromatids separate
Telophase II and cytokinesis
Nuclear envelope forms, cytoplasm separates. Results in four haploid daughter cells
Last four phases of meiosis II
Similar to those in meiosis I, however, the result is four haploid daughter cells
Each of the four daughter cells have two (haploid) chromosomes after meiosis II, from the original 4 chromosomes (diploid)
Main differences between meiosis and mitosis
Replication and separation of genetic material
Changes in chromosome number
Number of cell divisions
Similarities between meiosis and mitosis
Mitosis and meiosis are both types of cell division that occur in humans and other animals. They share the production of new cells and replication of genetic material
