Ch. 10 - How cells divide Flashcards
What is an example of a prokaryotic organism?
Bacteria
What process do prokaryotic organisms use to divide?
Binary fission.
What is binary fission?
A process where a cell divides into approximately equal halves.
What is a genome?
All of the genetic information (all the DNA)
How is the genome of bacteria stored?
In a circular strand
What is done before binary fission occurs?
The DNA is replicated.
What initiates the DNA replication?
When does it proceed?
A group of proteins.
Once the entire strand has been copied.
How large does the bacterial cell grow before splitting in half?
Twice its normal size.
Who first observed chromosomes, and when?
How was it discovered?
Walther Fleming in 1882.
By examining cell division of salamander larvae.
What are chromosomes composed of?
Chromatin.
What is chromatin composed of?
40% DNA and 60% protein.
How is the DNA found in each chromosome?
In one long unbroken strand.
How many nucleotides does a typical human chromosome contain?
140 million strands all strung together.
How many chromosomes are located in a cells nucleus?
46 chromosomes (23 pairs)
What are chromosome strands coiled around?
Histones.
What is the function of histones?
Proteins that package the DNA during cell division.
What is heterochromatin?
Highly condensed chromatin.
When is DNA packaged?
Only during cell division.
What is unpacked DNA called?
Euchromatin.
What constitutes the karyotype of chromosomes?
The difference in appearance (Length of the arms, the location of the centromere, the staining properties of the chromosome.)
How many pairs of chromosomes are there?
23 homologous pairs, and 1 pair of sex chromosomes.
What are homologous pairs of chromosomes?
Chromosomes that have the same genes on them (same karyotype), but the genes don’t have to code the same information.
What is an example of a trait that is coded by homologous pairs of chromosomes?
Eye color, hair type and color, height.
What are somatic cells?
Diploid (2n) which means they have two copies of the genome.
What cells are somatic?
All except sperm and eggs (46 chromosomes, 23 pairs).
What are gametes?
What type of cells are gametes?
Sperm and eggs.
Haploid (1n) (1 copy of the genome)
How many phases does the cell cycle have?
5 phases
What are the phases of the cell cycle?
1) G1 (part of interphase)
2) S (part of interphase)
3) G2 (part of interphase)
4) M (mitosis)
5) C (Cytokinesis)
What happens during the G1 phase of the cell cycle?
The primary growth phase of the cell which takes up most of the cell life.
What happens during the S phase of the cell cycle?
Where the cell synthesizes a copy of its genome.
What happens during the G2 phase of the cell cycle?
The cell prepares for division
1) The mitochondria and other organelles replicate.
2) The spindle apparatus starts to get organized.
3) The DNA starts to condense
What parts of the cell cycle are included in the interphase?
G1, S, and G2
What is the interphase of the cell cycle?
Part of the cell cycle between cell divisions.
What happens during the M (mitosis) phase of the cell cycle?
The DNA is divided.
How many stages are in the M (mitosis) phase of the cell cycle?
What are they?
4 stages.
1) Prophase
2) Metaphase
3) Anaphase
4) Telophase
What happens during the C (Cytokinesis) phase of the cell cycle and when does it occur?
1) Occurs at the end of the cell cycle.
2) The cytoplasm divide and two new daughter cells are formed.
3) The cell pinches in half.
4) A cell plate form between daughter cell in plants.
What happens during stage G0 of the cell cycle?
What is an example of a cell that is always in stage G0?
Cells aren’t going to divide at all or will last many years.
Nerve cells are always in the G0 stage.
During S phase, DNA is replicated and forms what?
2 sister chromatids.
What are sister chromatids?
Identical copies off the same gene.
What are sister chromatids held together by?
A centromere
What is a centromere?
A region of the chromosome that has a specific sequence and has special proteins associate with it.
The special proteins form a kinetochore, which is where spindle fibers attach (pull the sister chromatids apart into separate cells).
How can you tell when a cell has entered the prophase of mitosis?
1) The DNA starts to become visible under the light microscope.
2) Nuclear membrane disintegrates.
3) Nucleolus disappears.
4) Mitotic spindle begins to form
i) an array of microtubules
ii) centrioles move to opposite poles of the cell and the spindle fibers will go from the centrioles to the kinetochores of the chromosome.
iii) Plants don’t have centrioles, but spindle goes to the same place.
iv) At the poles the centrioles form an aster, which is a circular array of microtubules
5) Spindle attaches to kinetochores
How can you tell a cell has entered the metaphase of mitosis?
1) Chromosomes are aligned along the metaphase plate.
2) The metaphase plate is basically the equator of the cell
How can you tell a cell has entered the anaphase of mitosis?
1) Microtubules start to shorten, pulling the sister chromatids apart
2) The chromosomes start to move towards the poles of the cell via the shortening of the microtubules.
How can you tell a cell has entered the telophase of mitosis?
1) Chromosomes reach the poles of the cell
2) Kinetochores disappear
3) Nuclear membrane forms around DNA
4) Nucleolus reappears
5) DNA starts to unpack
6) Cytokinesis begins
How can you tell when a cell has entered the C (cytokinesis) phase?
When actin fibers start to squeeze the cell in half.
What is the term for cells pinching in half during cytokinesis?
Cleavage furrow.
In plant cells, after cytokinesis, what forms between the two new cells?
A cell plate.
In fungi and some protists, what happens?
The nuclear envelope does not dissolve, and mitosis occurs within the nucleus.
The cell then splits into two new cells.
What do the two new daughter cells have?
A full set of chromosomes and start the cell cycle over again.
How many control points do eukaryotic cells have along the cell cycle?
What are they?
3
G1 checkpoint, G2 checkpoint, M checkpoint.
What happens during the G1 checkpoint of the cell cycle?
1) Cell growth is assessed at the end of the first growth stage.
2) If the cell is ready, the S phase is started
3) It is at this stage where the determination to pass into a G0 resting stage is made
What happens during the G2 checkpoint of the cell cycle?
The success of the replication is checked, if everything is okay, mitosis starts.
What happens during the M checkpoint of the cell cycle?
This checkpoint occurs during metaphase, if everything is going well the cell finished mitosis, undergoes cytokinesis, and G1 starts over in the new daughter cells.
The levels of what control the checkpoints of the cell cycle?
Increasing levels of certain enzymes.
What is cell division a disease of?
Cell division
What is cell apoptosis?
Cell death.
What does the p53 gene code for?
Codes for the p53 protein which checks the DNA for damage and stimulates the activity of enzymes to fix the damage.
If damage cannot be repaired, the protein triggers apoptosis.
What happens if the p53 gene is badly damaged?
It can lead to cancer (won’t initiate cell death, and damaged cells will divide uncontrollably.
What can cause a mutation of the p53 gene?
Cigarette smoke.
What do mutations cause?
Changes in the protein coded from the gene, which can lead to a non-functional p53 protein.
What are the 2 kinds of growth factor?
Positive and negative.
What are positive growth factors?
Factors the stimulate cell division.
These factors trigger passage through the G1 checkpoint.
What are negative growth factors?
Factors that inhibit cell division.
These factors block the passage through the G1 checkpoint.
What are proto-oncogenes?
Genes that code for the proteins that stimulate cell division.
What are tumor suppressor genes?
Genes that code for the proteins that suppress cell division.
