Meiosis Flashcards
A special type of cell division of germ cells in sexually reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one copy of each chromosome.
Meiosis
A cell that contains both sets of homologous chromosomes
Diploid
Contain only a single set of chromosomes
Haploid
- In Meiosis the cell divides once into two identical daughter cells
- 2 divisions in meiosis (meiosis I and meiosis II
- The diploid cell becomes four haploid cells by the end of meiosis
Meiosis vs. Mitosis
A type of cell division that creates sex cells
Meiosis I
The initial and longest stage of the first meiotic division where homologous chromosomes pair up, condense, and exchange genetic material through the process of “crossing over,” resulting in genetic diversity before separating during the later stages of meiosis I.
Prophase I
Same as mitosis, the spindle fibers attach to the chromosomes and the homologous pairs line up in the middle
Metaphase I
The homologous chromosomes separate and move to the opposite poles of the cell
Anaphase I
The initial stage of the second meiotic division, where chromosomes condense again, the nuclear envelope breaks down, and a new spindle apparatus forms, preparing the cell to separate sister chromatids during the subsequent phases of meiosis II
Prophase II
The spindle fibers attach to the chromosomes and the homologous pairs line up in the middle
Metaphase II
The sister chromatids of each chromosome separate at the centromere and one pulled apart by microtubules, moving towards opposite poles of the cell, effectively distributing individual chromatids to different daughter cells.
Anaphase II
The separated sister chromatids reach the poles of the cell, nuclear membranes form around each set of chromosomes, and the chromosomes decondense, ultimately resulting in the division of the cell via cytokinesis to produce four haploid daughter cells, each with a single set of chromosomes.
Telophase II
- The cytoplasm of the cell physically divides into two separate daughter cells
- The two daughter cells produced during meiosis I further divide, resulting in the creation of four separate haploid daughter cells, each with a single set of chromosomes
Cytokinesis
The process by which reproductive cells, called gametes (sperm and egg), are created through a specialized cell division called meiosis, where a diploid cell undergoes two divisions to produce four haploid gametes, each containing half the number of chromosome as the parent cell.
Gamete Formation
- Mitosis can be a form of asexual reproduction, whereas meiosis is an early step in sexual reproduction
- There are three other ways in which mitosis and meiosis differ
- Replication and separation of genetic material
- Changes in chromosome number
- Number of cell divisions
Comparing Mitosis and Meiosis
- During both mitosis and meiosis, a complete copying or replication occurs
- In meiosis, homologous chromosomes line up and then move to separate daughter cells
-In mitosis, when two sets of material separates, each daughter cells receives one complete set of chromosomes - The sorting of genes and recombination of genes in meiosis result in a greater variety of possible gene mutations in meiosis
Replication and Separation
- Mitosis doesn’t normally change the chromosome number of the original cell
- A diploid cell that enters mitosis with 8 will divide to produce 2 diploid daughter cells, each of which also has 8 chromosomes
- Meiosis reduces the chromosome number by half
- A diploid cell that enters meiosis with 8 chromosomes will pass through 2 meiotic divisions to produce 4 haploid daughter cells, each with only four chromosomes
Changes in chromosome number
- Mitosis is a single division
- Meiosis requires two rounds of cell division, and in most organisms produces a total of four daughter cells
- Mitosis results in the production of 2 genetically identical daughter cells
- Mitosis Allows an organisms body to grow and replace cells
- Meiosis results in 4 genetically different haploid cells
Number of Cell Divisions
