Meiosis Flashcards
Gametes
Gamete, sex, or reproductive, cell containing only one set of dissimilar chromosomes, or half the genetic material necessary to form a complete organism (i.e., haploid)
Spermatogenesis
the production or development of mature sperm
Oogenesis
the production or development of an ovum.
Meiosis I
In meiosis I, chromosomes in a diploid cell resegregate, producing four haploid daughter cells. It is this step in meiosis that generates genetic diversity. DNA replication precedes the start of meiosis I. During prophase I, homologous chromosomes pair and form synapses, a step unique to meiosis.
Interphase
the resting phase between successive mitotic divisions of a cell, or between the first and second divisions of meiosis.
Prophase I
Chromosomes become visible, crossing-over occurs, the nucleolus disappears, the meiotic spindle forms, and the nuclear envelope disappears.
Metaphase I
The first metaphase of meiosis I encompasses the alignment of paired chromosomes along the center (metaphase plate) of a cell, ensuring that two complete copies of chromosomes are present in the resulting two daughter cells of meiosis I. Metaphase I follows prophase I and precedes anaphase I.
Anaphase I
The two chromosomes in each bivalent separate and migrate toward opposite poles.
Telophase I
Telophase I is the stage in meiosis I that follows after anaphase I. In anaphase I, the paired homologous chromosomes begin to separate from each other and move towards the opposite ends of the cell. This occurs as the kinetochore microtubules shorten, pulling and separating the paired chromosomes from each other.
cytokinesis I
The homologous chromosome pairs reach the poles of the cell, nuclear envelopes form around them, and cytokinesis follows to produce two cells.
Prophase II
Meiosis II begins without any further replication of the chromosomes. In prophase II, the nuclear envelope breaks down and the spindle apparatus forms.
Metaphase II
Metaphase II is the second stage in meiosis II. It follows prophase II, which primarily highlights the condensation of the chromosomes and the movement of centrosomes to polar regions of the cell.
Anaphase II
Anaphase II is the stage when sister chromatids of every chromosome separate and begin to move towards the opposite ends of the cell. The separation and the movement is due to the shortening of the kinetochore microtubules. Anaphase II precedes telophase II. Meiotic anaphase II is similar to the anaphase in mitosis.
Telophase II
During telophase II, the fourth step of meiosis II, the chromosomes reach opposite poles, cytokinesis occurs, the two cells produced by meiosis I divide to form four haploid daughter cells, and nuclear envelopes (white in the diagram at right) form.
cytokinesis II
A nuclear envelope forms around each set of chromosomes and cytokinesis occurs, producing four daughter cells, each with a haploid set of chromosomes.
