Cancer and Meiosis

Cancer is a result of uncontrolled cell division caused by mutations in genes that control the cell cycle. These mutations lead to the formation of tumors that can invade surrounding tissue.

Cancer treatments often target specific stages of the cell cycle to disrupt tumor cell division. Common targets include the G1 phase (cell growth and protein production) and S phase (DNA replication).

Meiosis is a specialized form of cell division that produces gametes with half the number of chromosomes (haploid) compared to normal body cells (diploid). This process is essential for sexual reproduction.

Definition: Cancer - A disease characterized by uncontrolled cell division forming tumors that can invade surrounding tissue.

Vocabulary: Gametes - Reproductive cells (sperm in males, egg cells in females) with a haploid number of chromosomes.

Highlight: Understanding the 3 stages of cell cycle GCSE AQA is crucial for comprehending both normal cell division and cancer development.

Genetic Variation in Gametes

Meiosis creates genetic variation in gametes through two main processes:

1. Crossing over of chromatids: During meiosis I, homologous chromosomes pair up, and chromatids exchange genetic material. This results in new combinations of alleles.

2. Independent segregation of chromosomes: The random separation of maternal and paternal chromosomes during meiosis I leads to different combinations of chromosomes in daughter cells.

These processes ensure that gametes produced through meiosis are genetically different from each other and the parent cell.

Definition: Crossing over - The exchange of genetic material between homologous chromosomes during meiosis, creating new combinations of alleles.

Highlight: The creation of genetic variation through meiosis is a key concept in GCSE AQA Biology and is essential for understanding evolution and inheritance.

Example: In humans, meiosis can potentially produce 2^23 different combinations of chromosomes in gametes due to independent assortment alone.