vastxtreme.blogg.se - Prophase description

PROPHASE DESCRIPTION FULL

The meiotic spindle fibres attach to one chromosome of each pair.The centrioles are now at opposites poles of the cell with the meiotic spindles extending from them.The chromosome pairs line up next to each other along the centre (equator) of the cell.The meiotic spindle, consisting of microtubules and other proteins, extends across the cell between the centrioles.At the end of Prophase I the membrane around the nucleus in the cell dissolves away, releasing the chromosomes.

The pairs of chromosomes may then exchange bits of DNA in a process called recombination or crossing over.The chromosomes pair up so that both copies of chromosome 1 are together, both copies of chromosome 2 are together, and so on.Each chromosome is composed of two sister chromatids containing identical genetic information.

The copied chromosomes condense into X-shaped structures that can be easily seen under a microscope.

During interphase, microtubules extend from these centrosomes.

Outside of the nucleus are two centrosomes, each containing a pair of centrioles, these structures are critical for the process of cell division.

PROPHASE DESCRIPTION FULL

The DNA in the cell is copied resulting in two identical full sets of chromosomes.

These are divided between the first time the cell divides (meiosis I) and the second time it divides (meiosis II): Meiosis I

Meiosis produces our sex cells or gametes (eggs in females and sperm in males).

These four daughter cells only have half the number of chromosomes of the parent cell – they are haploid.During meiosis one cell divides twice to form four daughter cells.