18 terms

Meiosis Stages

The process of meiosis creates 4 haploid gamete cells from a diploid cell. In animals these gametes are called eggs and sperm and in plants they are called eggs and pollen. For meiosis to occur it must go through two divisions, Meiosis I and Meiosis II. During Meiosis, the cell goes through the same stages as Mitosis (Interphase, Prophase, Metaphase, Anaphase, and Telophase/Cytokinesis), but it goes through these phases twice, but with some minor differences.
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Meiosis
Creates 4 haploid gamete cells from a diploid cell.
Interphase (Stage 1)
At this point the DNA is in its chromatin form and the DNA replicates.
Prophase I
The DNA starts to coil itself up into visible chromosomes. Homologous chromosomes pair up and exchange DNA in a process called
Crossing over.
Crossing over
Homologous Chromosomes (matching chromosomes from mom and dad) join up together and exchange share genetic information. Happens during Prophase I of meiosis.
Homologous Chromosomes
Matching chromosomes from mother and father. They are the same size, shape and carry genes for the same traits.
Metaphase I
The chromosomes line up down the middle along with their homologous pair.
Anaphase I
The homologous chromosomes pull apart from one another and move toward opposite poles.
Telophase I
Chromosomes are now at separate poles, nuclear membranes start to form around the 2 sets of chromosomes, and the chromosomes start to unwind back into chromatin. Cytokinesis occurs and the two cells split. These two cells are haploid at this point since each cell contains only 1 of each homologous pair. The next 4 phases occur to each of these cells.
Cytokinesis 1
This process cuts the cell into two new haploid cells
Prophase II
Notice that we skip interphase this time around because there is no replication of DNA between Meiosis I and Meiosis II.
At this point the chromosomes reorganize and the nuclear membranes start to dissolve again. Sister chromatids are joined by a centromere.
Metaphase II
The chromosomes line up down the middle of the spindles.
Anaphase II
The spindles pull the sister chromatids apart. Each goes towards a different pole.
Telophase II
Nuclear membranes start to form around the chromosomes again. A cleavage forms. Cytokinesis occurs and 4 haploid cells are formed. In females this creates egg cells and in males sperm cells.
Chromatin
Uncoiled DNA; thread like structures containing all genetic information (only "appears" during Interphase)
Meiosis 1
the separation of homologous chromosomes to create 2 new haploid cells from 1 diploid cell
Meiosis 2
the separation of sister chromatids to create 4 haploid gametes
sister chromatids
2 halves of a duplicated chromosome after DNA replication; they are connected by a centromere
centromere
The region of a chromosome where sister chromatids attach together