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_____ divide by binary fission.
How many chromosomes do humans have?
46 chromosomes in 23 nearly identical pairs.
What is chromatin?
Chromosomes are composed of chromatin, which is a complex of DNA and protein.
How many nucleotides are the typical human chromosome?
140 million nucleotides long.
What is a nucleosome?
Nucleosomes are complexes of DNA and histone proteins that promote and guide the coiling of DNA.
Histones are _____ charged and strongly attracted to _____ charged phosphate groups of DNA
What is a karyotype?
A particular array of chromosomes in an individual organism.
Which three processes occur in interphase (in the eukaryotic cell cycle)?
- 1. G1 (gap phase 1)
- 2. S (synthesis
- 3. G2 (gap phase 2)
What happens in G1 (gap phase 1)?
This is the primary growth phase, as well as the longest phase in the eukaryotic cell cycle. 1/3rd of the interphase process.
What happens in S (synthesis)?
DNA is replicated. 1/3rd of the interphase process.
What happens in G2 (gap phase 2)?
Chromosomes coil more tightly using motor proteins; centrioles replicate; tubulin synthesis. 1/3rd of the interphase process.
What happens in C (cytokinesis)?
The separation of 2 new cells. 1/5th of the eukaryotic cell cycle.
What is the centromere?
The constricted region joining the two sister chromatids that make up an X-shaped chromosome. Also the site where kinetochore is formed.
What are the 5 phases of the M (mitosis) phase?
- 1. Prophase
- 2. Prometaphase
- 3. Metaphase
- 4. Anaphase
- 5. Telophase
What happens during prophase?
The spindle apparatus assembles (2 centrioles move to opposite poles, forming the spindle apparatus). The nuclear envelope breaks down.
What are asters?
Radial array of microtubules in animals (not plants).
What happens during prometaphase?
A transition occurs after the disassembly of the nuclear envelope. The microtubules are attached to kinetochores. Chromosomes begin to move to center of cell (congression).
What happens during metaphase?
The alignment of chromosomes along the metaphase plate. This is the future axis of cell division.
What happens during anaphase?
Anaphase begins when the centromeres split. The key event is the removal of cohesin proteins from all chromosomes. The sister chromatids are pulled to opposite poles.
What are the two forms of movements involved in anaphase?
Anaphase A, where the kinetochores are pulled toward poles; and Anaphase B, where the poles move apart.
What happens during telophase?
The spindle apparatus disassembles, a nuclear envelope forms around each set of sister chromatids, chromosomes begin to uncoil, and nucleolus reappears in each new nucleus.
What is cytokinesis?
The division of the cytoplasm and the plasma membrane following the division of the nucleus resulting into two cells, each having it's own nucleus and cytoplasm surrounded by a plasma membrane.
What are the two irreversible points of the cell cycle?
- 1. The replication of genetic material
- 2. The separation of the sister chromatids
The cell cycle can be put on hold at specific points called _____.
What are the three checkpoints?
- 1. G1/S checkpoint (cell "decides" to divide, primary point for external signal influence)
- 2. G2/M checkpoints (cell makes a commitment to mitosis, assesses success of DNA replication)
- 3. Late metaphase (spindle) checkpoint (cell ensures that all chromosomes are attached to the spindle)
Tell me about germ-line cells.
- -Sex Cells
- -Used to Reproduce
- -Found in ovaries and testes
If it's not a germ-line cell, it's a _____.
Synonym for bacteria?
Prokaryote or archaea
What is the end result of mitosis?
Two genetically identical cells, with 1/2 of it's genetics from mom and 1/2 from dad.
What is the end result of miosis?
Four cells containing haploid sets of chromosomes.