Biology 2.6 Cell Divison - Meiosis Flashcards
What is meiosis
Meiosis is a type of cell division that produces gametes. Plays a key role in sexual reproduction and produces 4 genetically different cells that are haploid.
how many stages are there in meiosis
2 stages. Meiosis I and Meiosis II
what is the process in meiosis I
- Interphase: Cell grows and chromosomes replicate.
- Prophase I: Duplicated chromosomes condense and pair. *
- Metaphase I: Chromosome pairs align in the centre of the cell (metaphase plate). **
- Anaphase I: Spindle fibres separate homologous chromosomes to
opposite ends of the cell. - Telophase I: Cell pinches in the middle (cleavage furrow).
- Cytokinesis I: Cells separate, forming two different haploid cells.
what is the process of meiosis II
- Prophase II: Duplicated chromosomes condense.
- Metaphase II: Chromosomes align in the centre of the cell (metaphase plate).
- Anaphase II: Spindle fibres pull sister chromatids to opposite ends of the cell.
- Telophase II: Cell pinches in the middle (cleavage furrow).
- Cytokinesis II: Cells separate, forming four genetically different haploid cells.
what are the two process that allows genetic variation in meiosis
crossing over and independent assortment
What does it mean by crossing over
When homologous chromosomes pair, non-sister chromatids may touch, break, and re-join; exchanging genetic material.
The position where crossing over occurs is called chiasmata. Crossing over increase the genetic variation amongst gametes.
what does it by independent assortment
After crossing over, homologous chromosomes pair and align themselves at the metaphase plate. Each pair of homologous chromosomes align randomly, in other words they independently assort themselves. Independent assortment also increase the genetic variety in the gametes.
what is fertilisation
Fertilisation is random and contributes to genetic variation in offspring. Fertilisation restores diploid number.
