Mitosis and Meiosis Lecture Notes

Goals of Cell Division

• Mitosis:
  • Aim: Create two identical cells from the original.
  • Each daughter cell has the same DNA and organelles.
  • Process: Genetic material duplicates and separates into two new nuclei.
• Meiosis:
  • Aim: Produce four different cells with half the number of chromosomes.
  • Process begins similarly to mitosis but with key differences.

Meiosis Process

• Prophase: Homologous chromosomes exchange sections, increasing genetic variation.
• First Division: Homologous pairs separate.
• Second Division: Chromatids separate into single chromosomes.
• Result: Four different haploid cells, each with half the normal chromosome number.

Importance of Haploid Cells

• Purpose: Essential for sexual reproduction.
• Gametes (sperm and egg) are haploid, carrying half the chromosomes.
• Haploid (n): Represented by 'n'; humans have 23 chromosomes in sperm/egg.
  • Example: Human sperm and egg each have 23 chromosomes; together they form a zygote with 46 chromosomes (2n).

Zygote and Chromosome Numbers

• Zygote: Formed when sperm and egg combine, resulting in a diploid cell (2n).
• Chromosome numbers vary across species:
  • Humans: 46 chromosomes.
  • Fruit flies: 8 chromosomes.
  • Dogs: 78 chromosomes.
  • Lilies: 24 chromosomes.

Somatic vs. Sex Cells

• Somatic Cells:
  • Diploid (2n), all body cells except gametes.
• Sex Cells (Gametes):
  • Haploid (n), include sperm and egg.
  • Males produce sperm continuously from puberty (in testes).
  • Females are born with all eggs (in ovaries), releasing them post-puberty.

Interesting Facts

• Half of an individual's DNA existed in the mother years prior to fertilization.

Conclusion

• Importance of understanding mitosis and meiosis in reproduction and genetic diversity.
• Encouragement to engage with educational content on science topics.