Meiosis - Making Unique Cells for Reproduction

 

What is Meiosis?

• Meiosis is a special type of cell division that creates gametes (sperm and egg cells) for reproduction.
• Unlike mitosis, meiosis produces cells that are genetically different and have half the number of chromosomes.
• This is important as if not gametes (sperm, egg cell) when joined (form a zygote, fertilised egg) would have double the number of chromosomes that they should

Think of meiosis as a chef splitting a full cake (diploid) into two smaller portions (haploid), each with a unique flavor (genetic variety)!

 

Key Features of Meiosis

Feature	Explanation
Purpose	Produces gametes (e.g., sperm and eggs) for sexual reproduction.
Chromosome Number	Reduces the chromosome number by half (from diploid to haploid).
Genetic Variation	Creates genetically different cells due to shuffling of genes.

 

Diploid vs. Haploid

• Diploid (2n): Cells with two sets of chromosomes (e.g., body cells).
  Example in humans: 46 chromosomes (23 pairs).
• Haploid (n): Cells with one set of chromosomes (e.g., gametes).
  Example in humans: 23 chromosomes.

 

Why is Meiosis Important?

Function	Explanation
Gamete Production	Creates sperm and egg cells with half the chromosome number (haploid).
Maintains Chromosome Number	Ensures offspring have the correct diploid chromosome number when gametes fuse.
Genetic Variation	Shuffles genes, creating unique combinations that are important for evolution.

 

How Meiosis Works (Simplified Overview)

Meiosis happens in two rounds of division:

1. Meiosis I: Reduces the chromosome number by half (diploid /(\to/) haploid).
2. Meiosis II: Similar to mitosis, it separates the sister chromatids.

 

Key Steps in Meiosis

Stage	What Happens?
Replication	Chromosomes replicate before meiosis begins, creating identical copies (sister chromatids).
Meiosis I	Homologous chromosomes (pairs) separate. This reduces the chromosome number from diploid to haploid.
Meiosis II	Sister chromatids separate, creating four haploid gametes.

 

 

Meiosis vs. Mitosis

Feature	Mitosis	Meiosis
Purpose	Growth, repair, replacement	Production of gametes
Number of Divisions	1	2
Daughter Cells	2 identical cells	4 genetically different cells
Chromosome Number	Same as parent (diploid)	Half of parent (haploid)
Genetic Variation	None (identical cells)	Present (unique cells)