Flashcards in Chapter 6: Cell Division Deck (21):
Cell division that produces genetically identical daughter cells. Involves prophase, metaphase, anaphase, and telophase.
Cell division that occurs in sexually reproducing organisms, and produces haploid cells. Produces gametes, and the nucleus divides twice.
Makes up a replicated chromosome.
The center of a chromosome that holds two chromatids together.
The disc shaped protein on the centromere that attaches the chromatid to the mitotic spindle during division.
The sequence of growth and cell division.
Two important factors that limit cell growth and promote cell division: Surface area to volume ratio, and the capacity of the nucleus to control the whole cell.
Phases of the Cell Cycle
G1: Growth and biochemical activity.
S: Synthesis, DNA replication.
G2: Growth and preparation for mitosis.
Mitosis: The actual splitting of the nucleus.
- Nucleolus disappears.
- Nuclear envelope disintegrates.
- Chromatin begins to condense.
- Mitotic spindles begin to form.
- Chromosomes line up along the equator.
- Centrosomes are situated on opposite sides of the cell.
- Mitotic spindles connect the centrosomes through the kinetochores.
- Centrosomes begin to pull the chromosomes and the cell in opposite directions.
- Centrosomes and chromosomes cluster at their respective ends.
- Chromosomes begin to uncondense to their pre-mitosis state.
- When the individual nucleolus reappear, mitosis is complete.
The division of the cytoplasm. In animals, a cleavage furrow develops and pinches the cytoplasm, and in plants, a cell plate appears and creates a middle lamella.
Cells usually divide until they become too crowded. Cancer cells defy this, however.
Cells must be anchored to something to divide, such as a Petri dish or extracellular membrane. Cancer cells also defy this.
Where the homologous chromosomes separate. Involves synapsis and crossing over.
- Crossing over (nonsister chromatids exchanging genetic material).
- Synapsis (pairing of homologues).
- Chromosomes line up double file along the equator of the cell.
- Spindle fibers connect at the kinetochores.
- Homologous chromosomes are separated as they are pulled in opposite directions by the spindle fibers.
Telophase I and Cytokinesis I
- Chromosomes are pulled apart until they reach the opposite ends of the cell.
- Cytokinesis I usually occurs simultaneously with Telophase I, and splits the cell into two haploid.
Three Types of Genetic Variation
1. Independent Assortment of Chromosomes: each chromosome has two ways it can line up at the metaphase plate during meiosis I, which is randomly decided.
2. Crossing Over: the chromosomes randomly trade DNA segments.
3. Random Fertilization: the ovum and sperm have millions of chromosome options.