Mitosis and Cell Division

• A cell with a nucleus containing a pair of each chromosome is considered diploid.
• Mitosis is cell division where the nucleus divides, resulting in two cells with the same number of chromosomes as the original cell.
• Mitosis produces two genetically identical nuclei through DNA replication, creating two exact copies of DNA molecules (with rare mutations).
• During mitosis, these copies separate, so each new cell gets one copy of each DNA molecule in chromosome form.

Mitosis Phases

• Prophase involves chromosomes condensing through supercoiling and the breakdown of the nuclear membrane.
• Metaphase includes chromatid pairs aligning along the "equator," and proteins called spindle microtubules from the "poles" attach to the centromeres of chromatids.
• Anaphase is characterized by microtubules exerting force on centromeres, separating chromatids and pulling them to the poles.
• Telophase involves the formation of nuclear membranes and the creation of a furrow in animal cells, or a plate in plant cells.

Processes Involving Mitosis

• Development: Multicellular organisms begin as one cell undergoing many mitotic divisions.
• Tissue Repair: Torn tissue heals through the formation of new mitotically produced cells.
• Asexual Reproduction: Many unicellular organisms, like amoebas, reproduce by mitotic division.
• Tumors result from uncontrolled cell division and can occur in any tissue or organ.
• Reproduction is necessary for the continuation of a species.
• Meiosis is a division of the nucleus that results in nuclei with half the genetic material of the original cell.
• Cells produced by meiosis are gametes or sex cells (sperm and egg).
• Fertilization is the fusion of sperm and egg cells (gametes), producing a zygote with a complete set of chromosomes.
• Genes from two parents recombine in this process to form offspring.

Meiosis and Genetic Variation

• Crossing-Over: During meiosis I, chromosome strands connect or cross over, exchanging DNA between chromosomes inherited from male and female parents.
• Independent Assortment: During meiosis I, chromosomes inherited from each parent align in any order, producing gametes with different combinations of chromosomes from each parent.
• Mitosis involves one division of chromosomes, while meiosis involves two.
• Mitosis produces genetically identical cells, but meiosis produces cells that are not genetically identical.
• Mitosis produces cells containing all chromosomes needed, while meiosis produces cells containig half.
• Asexual reproduction derives all genetic information from one parent, while sexual reproduction involves two parents contributing half of genetic information.
• Asexual reproduction occurs via mitosis, the division of one cell into two genetically identical cells, whilst sexual reproduction uses meiosis to produce gametes that have half the genetic information.
• Mitosis is then used by the sexually reproducing organism during development.