Cellular Division Flashcards
Cell division functions in…
growth, repair and reproduction
The Two Types of Cell Divison
mitosis and meiosis
Mitosis
produced two genetically identical daughter cells and conserves the chromosome number (2n)
Meiosis
occurs in sexually reproducing organisms and results in cells with half the chromosome number of the parent cell
Chromosome
highly coiled and condensed strands of DNA; consists of two sister chromatids; the centromere is the region that holds chromatids together
Kinetochore
disc shaped protein on the centromere that attaches the chromatid to the mitotic spindle during cell division
The two factors that limit cell size and promote cell division.
- the ratio of the volume of a cell to the surface area
2. the capacity of the nucleus to control the entire cell
Cell Volume to Surface Area Ratio
the area of the cell membrane increases as the square of the radius while the volume of the cell increases as the cube of the radius; as a cell grow larger the volume increases at a faster rate than the cell membrane
Why does the ratio of the cell volume to surface area matter?
A cell depends on the cell membrane for the exchange of nutrients and waste products.
Capacity of the Nucleus
The nucleus must be able to provide enough information to produce adequate quantities to meet the cell’s needs.
Capacity of the Nucleus: Paramecium
This is a large, sophisticated cell with two nuclei that each control different cell functions.
Capacity of the Nucleus: Human Skeletal Muscle Cells
Giant, multinucleate cells
Five Major Phases of the Cell Cycle
G(1), S and G(2) which make up Interphase. Then, Mitosis and Cytokinesis.
Interphase: G(1) Phase
A period of intense growth and biochemical activity.
Interphase: S Phase
A period of synthesis and replication of DNA.
Interphase: G(2) Phase
A phase when the cell cycle grows and competes preparations for cell division.
Interphase
90% of life is spent here; Chromatin is threadlike and the nucleus contains one or more nucleoli. A single centrosome, consisting of two centrioles can bee seen in the cytoplasm. Plant cells lack centrosomes but have MTOCs.
Four Division of Mitosis
Prophase, Metaphase, Anaphase and Telophase
Prophase
The nuclear membrane begins to disintegrate and the strands of chromosomes condense. The nucleolus disappears. The mitotic spindle forms and begins to extend from one centrosome to the other. Longest phase of mitosis.
Metaphase
Chromosomes line up single file on the metaphase plate. Centrosomes are at opposite poles of the cell. Spindle fibers run from the centrosomes to the kinetochores of the centromeres.