Lecture 14: Mitosis Flashcards
How many nucleotides are in a chromosome?
hundreds of millions
How well packed must the DNA be?
very well, and very densely
Describe the process of DNA packing?
DNA first wraps around a histone protein the it folds and zig zags on itself until you get a dense chromosome
Define Mitosis
-mitosis is the dividing of the cell (and nucleus) into two new daughter cells
What is the physical separation of the diving cell into two called?
cytokinesis
How many steps are in mitosis? Name them
- there are four steps
- Prophase, Metaphase, Anaphase, Telophase
What does the centrosome consist of?
two centrioles
Differentiate between the centrosome and the kinetochore
- the centrosome forms poles at two ends of the calls and microtubules (mitotic sprindle fibers) stretch the two sides of the cell apart.
- kinetochore are proteins that attach to the centromere and bind the sister chromatids to the sprindle
Describe Early Prophase
it starts with DNA condensing to form chromosomes and the centrosomes move away from each other
Describe Late Prophase
the nuclear membrane disappears and the kinetochore attach the chromosomes to the sprindle fibers that are between the centrosomes
Describe Metaphase
pairs of sister chromatid have moved to the center of the cell forming a metaphase plate
Describe Anaphase
immediately follows metaphase, when the kinetochore pulls the two sister chromatid apart, one toward each centrosome.
Describe Telophase
Occurs when the chromosomes reach the centrosomes and each set of 46 chromosomes starts to have a nucleus forming around it. The DNA then starts to condense.
Define cleavage furrow
throughout mitosis, the cell has stretched wider, creating a cleavage furrow.
When does cytokinesis happen and describe it.
- near the end of telophase
- microfilaments inside the cell called contractile ring tighten, causing the cell to snap in two
