Lecture Notes: Cell Reproduction and Division

Introduction to Cell Reproduction

• Cells reproduce using a process called cell division.
• New cells created are referred to as daughter cells.

Unicellular Organisms

• Unicellular organisms such as bacteria reproduce through cell division by cloning themselves.
• This process results in two daughter cells that are genetically identical to the parent cell.
• Known as asexual reproduction; specifically, binary fission.

Multicellular Organisms

• In multicellular organisms, cell division results in new cells that are part of the organism.
• Purpose: Allow growth and replacement of cells (e.g., healing a paper cut).

Specialized Cell Division for Sex Cells

• Gametes are sex cells produced via a modified cell division process.

Chromosomes and Cell Division

The Role of Chromosomes

• Chromosomes are crucial in cell division.
• Found in the cell's nucleus as deoxyribonucleic acid (DNA).
• DNA holds the genetic instructions for the organism.
• Normally, DNA appears grainy in the nucleus as chromatin.

DNA Replication

• Before cell division, DNA replicates to pass information to daughter cells.
• DNA condenses into X-shaped structures called chromosomes.
• Chromosomes consist of two sister chromatids, joined by a centromere.

Chromosome Numbers

• Different organisms have varying numbers of chromosomes.
• Somatic cells: typical body cells, contain 23 pairs (46 total) in humans.
• Gametes: have one chromosome from each pair (23 total).
• Gametes are not genetically identical to parent cells.

Fertilization and Zygote Formation

• Fertilization involves a sperm cell and an egg cell each contributing 23 chromosomes.
• The result is a zygote with 23 pairs of chromosomes (46 total).

Conclusion

• Understanding cell division prepares you to study the cell cycle, which is the overall life cycle of the cell.