2.6 - Cell Division (Meiosis) Flashcards
What do somatic cells (body cells) consist of?
Pairs of chromosomes
one from mother, one from father = homologous pairs
What is the term used for a cell consisting of homologous pairs?
Diploid
What happens during meiosis?
Chromosomes are divided so that each daughter cell (sex cell) receives half the original number.
What is the term used for a cell consisting of one set of chromosomes (combination from each parent)?
Haploid
What does fertilisation restore?
Diploid number
What fertilisation contribute to?
It is random and contributes to genetic variation in offspring.
What is meiosis?
A type of cell division that produces gametes (sex cells: eggs and sperm) and plays a key role in sexual reproduction.
What are the products of meiosis?
Four genetically different cells that are haploid (they only have one copy of each chromosome).
What two main stages does meiosis occur?
- Meiosis I
2. Meiosis II
When are chromosomes replicated in meiosis?
During interphase before meiosis I.
Genetic variation is produced through what two processes?
- Crossing Over
2. Independent Assortment
What is crossing over?
After DNA replication when the homologous pairs chromosomes pair, non-sister chromatids may touch, break and rejoin; exchanging genetic material.
When does independent assortment occur?
After crossing over.
What is independent assortment?
After crossing over, homologous chromosomes pair and align themselves at the metaphase plate.
Each pair of chromosomes aligns randomly, where they “independently assort” themselves.
What does independent assortment increase?
Genetic variation in gametes.
