LAB 3: Cell Division

• What are the typical features of a plant cell in telophase?

  Spindle begins to disappear, chromosomes begin to disperse, nucleoli begin to form, nuclear envelopes begin to assemble, a new cell wall (cell plate) begins to form
• Where does meiosis occur in humans?

  Reproductive organs
• How do prokaryotes reproduce?

  Prokaryotes reproduce through a process called binary fission, where the cell divides into two identical daughter cells. This is a form of asexual reproduction that allows prokaryotes to rapidly increase their population.
• What is mitotic cell division?

  The process that produces two daughter cell that are nearly identical to their eukaryotic parent cell. It is responsible for reproduction in unicellular eukaryotes, and for growth and tissue repair in multicellular eukaryotes.
• What are the phases of the cell cycle?

  Interphase, mitosis, cytokinesis.
• Interphase is divided into three periods:

  • G1 (Gap 1), during which the cell builds proteins and grows larger.
  • S (Synthesis of DNA), during which the cell continues to grow but now is copying its nuclear DNA as well.
  • G2 (Gap 2), during which the cell is still growing as final preparation are made for cell division.
• Mitotic phase consists of two parts:

  • division of the nucleus (mitosis)
  • division of the whole cell (cytokinesis)
• How many chromosomes are in the nucleus of a human cell?

  46
• • The whole is called a chromosome, while each side of the "X" is called a chromatid.
  • The point of attachment between the two chromatids is called the centromere.
• What are the phases of mitosis?

  Prophase, prometaphase, metaphase, anaphase and telophase.
• What occurs in prophase of a plant cell?

  Chromosomes condense and becomes visible, nucleolus disappears, spindle starts to form.
• What occurs in prometaphase of a plant cell?

  Nuclear envelope breaks up, spindle attaches to centromeres and begins to pull on chromosomes.
• What occurs in metaphase of a plant cell?

  Spindle pulling on the centromeres causes the chromosomes to line up along the middle (at the metaphase plate).
• What occurs in anaphase of a plant cell?

  Chromatids breaks free of each other and are pulled to either end by the spindle (each free chromatid is now considered a chromosome).
• If a diploid parent cell had 16 chromosomes (2n=16), how many has each daughter cell?

  16
• Which part of the cell cycle takes the longest time?

  Interphase
• What occurs in prophase of an animal cell?

  Cell rounds up as cytoskeleton breaks down, chromosomes condense and become visible, nucleolus disappears, spindle starts to form.
• What occurs in prometaphase of an animal cell?

  Nuclear envelope breaks up, spindle attaches to centromeres and begins to pull on chromosomes, centrosomes (with centrioles) begin to move to either end of the cell.
• What occurs in metaphase of an animal cell?

  Spindle pulling on the centromeres causes the chromosomes to line up along the middle (the metaphase plate).
• What occurs in anaphase of an animal cell?

  Chromatids break free of each other and are pulled to either end by the spindle (each free chromatid is now considered a chromosome), entire cell elongates.
• What occurs in telophase of an animal cell?

  Spindle begins to disappear, chromosomes begin to disperse, nucleoli begin to form, nuclear envelopes begin to assemble, the cell begins to pinch in (cleavage furrow).
• If the diploid parent cell had 82 chromosomes (2n=82), how many has each daughter cell?

  82
• Comparing mitosis in plants with mitosis in animals, what are the differences?

  Mitosis in animals forms a cleavage furrow in telophase, while mitosis in plants forms a cell wall.
• During sexual reproduction, two cells (called gametes) fuse to form a new cell.
• Mitosis of a diploid cell will always produce diploid cells, so a different kind of cell division is required to produce haploid cells. This specialized cell division is called meiosis.
• Meiosis in animals typically only takes place in certain cells of the gonads (ovaries and testes).
• What is meiosis?

  A process that terminates with the production of haploid cells (such as gametes).
• Meiosis involves two cell divisions, called meiosis I and meiosis II, which may result in four daughter cells.
• In prophase I the chromosomes condense right next to their homologue, forming homologous pairs (this is when crossing over occurs).
• During metaphase I these homologous pairs line up along the metaphase plate.
• During anaphase I, the homologous pairs of chromosomes are pulled apart.
• Each daughter cell of meiosis I receives one chromosome (with two chromatids) from each homologous pair, and therefore has half the number of chromosomes (n) as the parent cell (2n).
• Meiosis II is virtual identical to mitosis (prophase II, metaphase II, anaphase II and telophase II), but because it starts with two cells that have n chromosomes each, it produces four cell with n chromosomes each.
• The cells produced by meiosis may then mature into gametes, and the entire process from 2n cell to gamete is called gametogenesis.
• What is spermatogenesis?

  When male gametes (sperm) are produced in the testes of animals.
• What is oogenesis?

  When female gametes (ova, or eggs) are produced in the ovaries of animals.
• In spermatogenesis, a primary spermatocyte begins meiosis I, which results in two secondary spermatocytes. Meiosis II than results in four spermatids, which mature into spermatozoa.
• In oogenesis, the process can be somewhat more complex. In humans, a primary oocyte begins meiosis I but cytokinesis is unequal, producing one secondary oocyte (with almost all of the cytoplasm) and one polar body (which is discarded).
• In oogenesis, the secondary oocyte then undergoes meiosis II, also with unequal cytokinesis, producing one ootid and another polar body. The ootid then matures into an ovum (egg). When an ovum is fertilized by a spermatozoan, it is then called a zygote.
• What are the differences between mitosis and meiosis?

  Meiosis produces haploid cells and mitosis produces diploid cells. Meiosis involves two cell division while mitosis does not. In prophase of mitosis the chromosomes do not condense next to any other chromosome while in prophase I of meiosis the chromosomes condense next to their homologue, forming homologous pairs.