Exploring the Fascinating World of Cell Division: Understanding Mitosis, Meiosis, and Their Crucial Roles in Growth, Development, and Reproduction Across Diverse Organisms in the Biological Realm of Life's Continuity and Genetic Diversity.

Cell division is a fundamental biological process by which a parent cell divides into two or more daughter cells. This process is essential for growth, development, and tissue repair in multicellular organisms. The mechanisms of cell division vary significantly between prokaryotic and eukaryotic cells, reflecting their structural and functional differences.

1. Cell Division (DNA replication and Mitosis) M7.1 Illustrate the mechanism of semi-conservative replication through complementary base-pairing. M12.1 Understand that DNA is perpetuated by semi-conservative replication. C8.1 Explain why the amount of DNA in a cell doubles before division. C8.2 Describe how prokaryotic cells divide by binary fission. C8.3 Illustrate the process of mitosis in eukaryotic cells. C8.4 Know that the products of mitotic division or binary fission have the same number and type of chromosomes as the parent.

2. Semi-conservative DNA replication Before a cell divides to produce two identical cells the total amount of DNA must double so that each daughter cell receives an identical copy of the genetic information. This occurs through a process called DNA replication. DNA replication is referred to as “semi-conservative” because each new strand of DNA contains one of the existing strands.

3. Semi-conservative DNA replication Firstly, the complementary strands of DNA separate. Each strand serves as a template for making the new complementary strand. DNA nucleotides (A, T, C & Gs ) are paired to the template strands by DNA polymerase. There are now 2x double stranded DNA molcules which are an exact replica of the original, with one “old” strand and one “new” strand each.

4. Semi-conservative DNA replication Even though the amount of DNA in a cell doubles after DNA replication, the number of chromosomes stay the same. Each chromosome now has two identical chromatids instead of one.

5. DNA is perpetuated by semi-conservative replication DNA is unique in the way that it makes other copies of itself. DNA is not just created but rather is perpetuated or passed on through the process of semi-conservative replication.

6. Binary Fission: Cell division in Prokaryotic cells Binary fission means “dividing in half” Prokaryotes, such as bacteria, usually have a single chromosome made of double stranded DNA. The DNA replicates before the cell membrane pinches off and divides the cell into two daughter cells in a process called cytokinesis. Each daughter cell will get an identical copy of the DNA (unless mutation occurs) which means that there is minimal genetic variation.

7. Mitosis: Cell division in Eukaryotic cells All cells go through the cell cycle which is made of three parts: Mitosis- division of the nucleus Cytokinesis- division of the cytoplasm and the formation of two new daughter cells Interphase- A time for growth (G 1 ) DNA replication (S) and preparation for division ( G 2 )

8. Parent cell Daughter cells

9. Centrioles are proteins that act as anchors at opposite poles of the cell. They are important at pulling the chromosomes apart and dividing the cell into 2 daughter cells. The mitotic spindle attached the centrioles and centromeres (on the middle of the chromosome) Key parts of the cytoskeleton in cell division

10. We give special names to each of the different “phases” of the mitosis. We remember them with the acronym PMAT . pmat P- Prophase M- Metaphase A- Anaphase T- Telophase

11. PROphase Stage 1 Prophase: The DNA in the form of chromatin starts to thicken. The chromosomes are made of two identical sister chromatids. The nuclear membrane breaks down and chromosomes move into the cytoplasm. Centrioles move to the poles of the cell.

12. metaphase Stage 2 Metaphase: The chromosomes line up on the cell’s equator (the metaphase plate). The mitotic spindle attaches to the centromeres of each chromosome.

13. anaphase Stage 3 Anaphase: The chromosomes divide and sister chromatids are drawn apart. The chromatids are drawn towards opposite poles by the constriction of the mitotic spindle which are attached to the centromeres.

14. telophase Stage 4: Telophase : As the chromatids are drawn to opposite poles, daughter nuclei begin to form. The chromosomes uncoil to form chromatin and cytokinesis occurs where the cell pinches off to form two separate daughter cells.

15. Both of the daughter cells are now in interphas e…

16. Mitosis (bone cell slides)

17. No genetic variation from mitosis or binary fission. One division of mitosis/binary fission produces 2 identical daughter cells Unless mutations arise, each daughter cell is a clone or exact copy of the parent cell with the same number of chromosomes and same genes of the chromosomes. Mitosis is vital for growth, repair and asexual reproduction. Sex cells (sperm and egg cells) divide through a different type of cell division called meiosis which allows for genetic variation (unlike mitosis). Meiosis will be the focus of the next video.