IB Biology Topic D2.1.4: Roles of Mitosis and Meiosis in Eukaryotes Notes

Mitosis and Meiosis Play Different Roles in Eukaryotes

1. Eukaryotic cells divide using two distinct processes that serve opposite purposes.
2. Mitosis produces genetically identical cells for growth, repair, and asexual reproduction.
3. Meiosis produces genetically varied haploid gametes for sexual reproduction.

Mitosis Makes Identical Diploid Cells for Growth and Repair

1. Growth adds new cells so a multicellular organism can increase in size.
2. Tissue repair and cell replacement replace cells that are damaged, worn out, or lost.
3. Embryonic development builds a whole organism from a single fertilised egg.
4. Asexual reproduction lets some eukaryotes, such as certain protists and plants, produce offspring from one parent.
5. In every case mitosis produces genetically identical diploid daughter cells with the same chromosome number as the parent.

Meiosis Halves the Chromosome Number to Make Gametes

1. Meiosis produces haploid gametes, such as sperm and egg cells, or spores in some organisms.
2. It halves the chromosome number, turning one diploid cell into haploid cells.
3. This halving is essential for sexual reproduction.
   1. When two haploid gametes fuse at fertilisation, the normal diploid number is restored.
   2. Without halving, the chromosome number would double every generation.
4. Meiosis also generates genetic variation, so the gametes it makes are genetically different from each other.

Mitosis and Meiosis Contrast in Purpose and Outcome

1. Mitosis gives two diploid daughter cells that are genetically identical to the parent.
2. Meiosis gives four haploid cells that are genetically varied.

Both Processes Are Essential to a Species

1. Mitosis keeps an individual organism alive by growing and maintaining its body.
2. Meiosis keeps a species going by producing varied gametes for the next generation.