meiosis Flashcards
what is meiosis?
Meiosis is a type of cell division in which a parent cell divides to form four haploid cells, each genetically distinct from one another.
what happesn in interphase before meiosis?
DNA is replicated during interphase so that each chromosome contains two chromatids.
what happens in meiosis 1
Homologous chromosomes are separated.
what happens in meiosis 2
Chromatids are separated.
what type of division does meiosis do?
a reduction division in which the chromosome number is halved to form haploid cells. These haploid cells form the gametes (egg and sperm cells) in animals and plants.
what happens in prophase 1?
The chromosomes condense and homologous chromosomes pair up. Centrioles migrate to opposite poles of the cell where each centriole starts forming spindle fibres. The nucleolus disappears and the nuclear envelope starts to break down, leaving the chromosomes free in the cytoplasm.
what happens in metaphase 1?
Chromosomes line up along the equator of the cell in their homologous pairs (so in humans, 23 pairs line up).Each chromosome attaches to the spindle by their centromere.
what happens in telophase 1?
The chromosomes reach the opposite poles of the cell where they uncoil. A nuclear envelope forms around each set of chromosomes and the nucleolus starts to reform. t he cytoplasm divides to form two cells (cytokinesis).
what happens in anaphas 1
Homologous chromosome pairs are separated and pulled to opposite poles of the cell (chromatids stay joined together)
what happens in telophase 1
The chromosomes reach the opposite poles of the cell where they uncoil.
A nuclear envelope forms around each set of chromosomes and the nucleolus starts to reform.
The cytoplasm divides to form two cells (cytokinesis
what happens in prophase 2
The chromosomes condense and are now visible under a microscope.
Centrioles migrate to opposite poles of the cell where each centriole starts forming spindle fibres.
The nucleolus disappears and the nuclear envelope starts to break down
what ahppens in metaphase 2?
The chromosomes line up at the equator of the cell (so in humans, 23 chromosomes line up).
Each chromosome attaches to the spindle by their centromere.
what happens in anaphase 2
The centromeres divide and separate each pair of chromatids.
The spindle fibres contract and shorten to pull the chromatids to opposite poles of the cell.
what happens in telophase 2
The chromatids reach the opposite poles of the cell where they uncoil to become long and thin again.
A nuclear envelope forms around each set of chromosomes to form two nuclei and the nucleolus starts to reform.
The cytoplasm divides (cytokinesis) and 4 cells are produced.
