Meiosis | Biology for GCSE/IGCSE - Year 11 PDF Download

Meiosis

• Meiosis, a form of nuclear division, yields genetically diverse cells.
• Its primary function is to generate gametes, or sex cells.
• During gamete formation, the chromosome count must be reduced by half.
• Failure to halve the chromosome count would result in a doubling of chromosomes upon fertilization.
• Meiosis accomplishes this reduction, transitioning from diploid to haploid cells, ensuring genetic diversity.
• The process initiates with chromosome duplication, similar to mitosis, followed by two rounds of division.
• Through these divisions, each gamete receives only one set of chromosomes, rendering them haploid.
• Meiosis ultimately produces four haploid cells due to its double division.

Process

• Each chromosome duplicates, forming X-shaped chromosomes.
• In the first division, chromosomes pair up in the cell's center, undergo recombination, and are separated by cell fibers, resulting in each new cell having one of each recombinant chromosome pair.
• The second division involves chromosomes lining up at the cell's center, with cell fibers separating them, similar to mitosis. This process yields four haploid daughter cells.

Importance of Meiosis

• Meiosis is crucial for the production of gametes like sperm cells, egg cells, pollen grains, and ovum.
• It enhances genetic variation among offspring, contributing to diversity.

Variation in Meiosis

• Meiosis generates diversity by creating new combinations of maternal and paternal chromosomes with each gamete production.
• During fertilization, the random fusion of gametes results in each offspring being genetically distinct from others.

Differences between Mitosis & Meiosis