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Mitosis

Terms in this set (23)

Chromosome
1 strand of DNA.
Unduplicated Chromosome
A chromatid.
Duplicated Chromosome
Two identical sister chromatids.
Helicase Enzyme
Unwinds DNA by breaking hydrogen bonds between base pairs.
DNA polymerase
Grabs free-floating nucleotides and binds it to complementary bases.
Ligase
Creates new hydrogen bonds. After ligase does its job, a new identical DNA strand exists.
What does DNA look like during interphase?
Spaghetti - it is a huge pile of uncondensed molecules called chromatin.
How do chromosomes form?
DNA binds with histones to form chromatin, but chromatin isn't condensed until mitosis. (In prophase of mitosis, condensed chromatin forms chromosomes.)
How many chromosomes is a human genome made of?
46 chromosomes total (two sets of 23 chromosomes). Each parent contributes one set of 23 chromosomes.
Mitosis
A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent cell. All somatic, or "body" cells, do this type of asexual reproduction.
Prophase
The longest phase!
1) Chromatin condenses into chromosomes
2) Centrioles (two tiny structures in the cytoplasm near nuclear envelope) separate and move to opposite sides/poles of the cell
3) Spindle fibers begin to form
4) Nucleolus disappears, and nuclear envelope breaks down
Metaphase
Chromosomes line up across the center of the cell. Spindle fibers attach to the kinetochore in the centromere and pull the chromosomes apart; sister chromatids separate.
Anaphase
Separated chromatids move to opposite ends of the cell. Nuclear envelope begins to re-form.
Telophase
Chromosomes, which were condensed, begin to disperse into a tangle of chromatin again. A nuclear envelope completely re-forms around each cluster of chromosomes. Spindle fiber begins to break down. A nucleolus becomes visible... now, there ARE TWO NUCLEI.
Cytokinesis
This occurs around the same time of telophase, and divides the cytoplasm to create two new cells. In animal cells, the membrane is drawn inward until the cytoplasm is pinched into two parts. In plants, a cell plate forms between the two nuclei. The plate gradually develops into a separating membrane, and the cell wall begins to appear.
How would the size of each daughter plant/animal cell compare to the parent cell?
Right after cell division, the daughter cell would be half the size of the parent cell, but it will rapidly grow during the cell cycle to become the same size as the parent cell.
Why would animal cells need a special structure for spindle fiber attachment while plants don't?
Plant cells have a rigid cell wall so spindle fibers can attach straight to the wall. Animal cells are flexible and not rigid, centrioles are needed to pull apart the chromosomes.
What is the longest and shortest phase of mitosis?
Prophase is the longest and anaphase is the shortest.
What evidence shows that mitosis is a continuous process?
Because all cells change at different times and not all at the same time, it shows that mitosis is a multi-step continuous process. Also, because the cycle keeps repeating, it is a continuous process that does not end.
A single cell has X number of chromosomes. How many chromosomes are in the cell at each phase of mitosis?
Interphase: X cells (because the cell has not yet divided and is still a single cell)
Prophase/Metaphase/Anaphase: 2X cells (because the DNA has replicated and now one cell has twice the amount of DNA required)
Telophase: X cells (because the DNA has now been split among two cells)
Where does mitosis occur?
In somatic/body cells (i.e. blood cells, bone, skin, etc.).
How many cells, and what type (haploid or diploid) do you end with?
You start with one diploid cell, and end with two diploid cells.
Why does a cell divide?
1) to maintain surface area to volume ratio
2) so the org. can grow and develop
3) to replace dead/damaged cells
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