4.3.7 The Outcomes & Processes of Mitosis & Meiosis

Mitosis

1. Purpose:

• Produces two genetically identical diploid daughter cells.
• Essential for growth, repair, and asexual reproduction.

2. Process Overview:

• Involves one division.
• Chromosomes replicate during interphase.
• Each daughter cell receives an identical copy of the genetic material.

3. Outcomes:

• Maintains the same chromosome number as the parent cell (e.g., 46 chromosomes in humans).
• Ensures genetic stability by producing clones.

Meiosis

1. Purpose:

• Produces four genetically diverse haploid gametes.
• Required for sexual reproduction, ensuring genetic variation in offspring.

2. Process Overview:

• Involves two divisions:
• Meiosis I separates homologous chromosomes.
• Meiosis II separates sister chromatids.
• Crossing over and independent assortment occur during meiosis I, introducing genetic diversity.

3. Outcomes:

• Reduces the chromosome number by half (e.g., from diploid 46 to haploid 23 in humans).
• Produces gametes that are genetically different from one another and the parent cell.

Comparison of Outcomes

Feature	Mitosis	Meiosis
Purpose	Growth, repair, asexual reproduction	Sexual reproduction (gamete formation)
Number of Divisions	1	2
Number of Daughter Cells	2	4
Chromosome Number	Diploid (same as parent)	Haploid (half of parent)
Genetic Variation	None (identical cells)	High (due to crossing over and independent assortment)

Key Features to Remember

• Mitosis:
  • Results in no genetic variation.
  • Chromosome number remains constant.
• Meiosis:
  • Ensures genetic variation through:
  • Crossing over (exchange of genetic material between homologous chromosomes).
  • Independent assortment (random alignment of homologous pairs during metaphase I).