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Cell Reproduction

Dive into the intricate world of cell reproduction through mitosis and meiosis. Learn about chromosomes, cell cycles, and the stages of cell division. Explore how cells maintain proper chromosome numbers and how sex cells are formed.

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Cell Reproduction

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  1. Cell Reproduction Chromosomes, Mitosis, and Meiosis

  2. Chromosomes • Growth and development of cells are carefully controlled by chromosomes found in the nucleus • Eukaryotic chromosomes are made up of chromatin

  3. Chromosomes • A set of chromosomes is called a karyotype. • Humans have 46 chromosomes • Chromosomes are sorted by size and shape into 23 pairs.

  4. Chromosomes • When a human cell contains 23 pairs of chromosomes, (46 total chromosomes) it is said to be diploid. Somatic Cells or body cells are an example of diploid cells. • Cells which contain only one copy of chromosomes (23 total chromosomes) are said to be haploid. Gametes or sex cells are an example of haploid cells.

  5. Chromosomes • Sex cells determine whether you are male or female • If you have an XY combination, you are a male • If you have an XX combination, you are a female

  6. Cell Cycle

  7. Cell Cycle • Mitosis and cytokinesis are a small portion of the cells life cycle • The cell cycle can be divided into five phases • Mitosis • Cytokinesis • G1 Phase • S Phase • G2 Phase

  8. Interphase • G1: Starts with daughter cells and is the period of rapid growth before the DNA is replicated.

  9. Interphase • S phase is the period in which the DNA is duplicated.

  10. Interphase • G2 is the phase in which the cell has duplicated it’s DNA and the cell prepares for division.

  11. Mitosis • Mitosis is the process in which the nucleus divides to form two complete new nuclei • Mitosis can be broken down into six main phases • DNA Replication • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis

  12. Mitosis

  13. Step One: DNA Replication • Chromosomes are not yet visible because they are extended and uncoiled • The DNA of each chromosome is copied • Each chromosome is composed of two identical strands

  14. Step Two: Prophase • Mitosis begins • The chromosomes coil into short, fat rods • The nuclear envelope breaks up • A network of protein cables called spindle fibers assembles across the cell

  15. Prophase

  16. Step Three: Metaphase • Chromosomes attach to the spindle fibers and line up in the center of the cell

  17. Metaphase

  18. Step Four: Anaphase • Each chromatid separates from its identical copy • Chromosomes are reeled to opposite sides of the cell • The spindle fibers begin to break down

  19. Anaphase

  20. Step Five: Telophase • Each side of the cell now has a complete set of chromosomes • A nuclear envelope forms around each new set of chromosomes • The chromosomes uncoil so that proteins can be built • The spindle fibers disappear

  21. Telophase

  22. Step Six: Cytokinesis • The cytoplasm is pinched in half, forming two new cells • Each new cell contains identical DNA • After growth and replication, these cells may divide again

  23. Cytokinesis

  24. Meiosis • Meiosis is a two stage form of nuclear division in which the chromosome number is halved • This is the formation of the gametes or sex cells (sperm and egg)

  25. Step One • One member of each chromosome pair is from one parent; the other is from the other parent

  26. Step Two • First the amount of DNA doubles • The similar chromosomes pair with one another • Occasionally, paired chromosomes will exchange segments in a process called crossing-over

  27. Step Three • The first meiotic division (meiosis I) separates the member of each pair of chromosomes • Meiosis I reduces the number of chromosomes by one half.

  28. Step Four • The second meiotic divisions (meiosis II) separates the two copies of each chromosome (the chromatids) • Cell division now occurs, producing four haploid cells.

  29. Step Five • During sperm formation, the four cells containing these nuclei develop head and tails • During egg formation, only one of the cells containing these nuclei becomes a mature egg; the other three cells usually die

  30. Meiosis

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