The cell cycle (mitosis) Flashcards
What occurs during Metaphase?
chromosomes line up at the equator of the spindle (and cell)
Name the phase during which DNA and organelles are replication occurs.
interphase
Describe and explain what a cancer drug may do to kill or supress cancer cells
- damage the cells so longer time to recover;
- reduced rate of mitosis
- increased doubling time;
Explain why meiosis is important in sexual reproduction
produces haploid cells (chromosome number halved) for fertilisation;
maintains the diploid number in next generation;
Describe what happens in anaphase
identical chromatids move to opposite poles
Other than DNA and organelles increasing, what other PROSSES need to INCREASE for mitosis to occur?
1 of:
- ATP production
- protein synthesis
- replication of centrioles
Describe the role of the spindle during mitosis.
they attach to the centromeres (of the chromosomes) and separate chromatids to the opposite poles of the cell
Describe and explain how the structure of DNA results in accurate replication.
- made up of two strands therefore semi-conservative replication is possible;
- hydrogen bonds holds strands together
- hydrogen bonds are easily broken so allow strands to separate;
- base is sequence exposed so it acts as a template so can be copied;
- complementary base copying occurs as;
- so the DNA is one sense and one new strand;
Describe the behaviour of chromosomes during mitosis and explain how this results in the
production of two genetically identical cells.
1.chromosomes condense.
2.chromosomes are each identical copies due to replication;
3.chromatids move to equator of the cell;
4. and attach to individual spindle fibres;
5.spindle fibres attach to the centromeres and divide the chromosomes into chromotids;
6.chromatids move to opposite poles of the cell;
7.each pole receives
identical copies of each chromosome;
8.nuclear envelope forms around each group of
chromatids
Drugs are being developed which only kill cells in a
low oxygen environment. Suggest how these drugs could be useful in the treatment of
cancer.
cancer cells killed, normal body cells survive;
cancer cells low oxygen (as blood supply cannot satisfy demand);
Explain the
advantage of cells completing the cell cycle in a short time.
replace cells quickly
Mikanolide is a drug that inhibits the enzyme DNA polymerase. Explain why this drug may
be effective against some types of cancer.
Prevents DNA replication as nucleotides of new strand are not joined
as sugar-phosphate bonds are not formed;
therefore Prevents mitosis;
If the DNA of the cell is damaged, a protein called p53 stops the cell cycle.
Mutation in the gene for p53 could cause cancer to develop. Explain how.
Cancer cells often have damaged DNA;
p53 is therefore not made;
Cell with faulty DNA divides;
Uncontrolled division produces cancer;
Describe the stages of mitosis
- S(ynthesis)-phase (interphase) - DNA replication occurs
- Prophase - Chromosomes condense and shorten and become visible
- Metaphase - chromosomes align at the equator of the cell
- Anaphase - spindle fibres attach to the centromere of the chromosome and pull each chromatid to opposite pole of the cell
- Telophase - nuclear envelope re-forms at the groups of the chromatid at each pole of the cell
What happens in G1 (first growth) stage?
- when the proteins from which cell organelles are synthesized are produced
What happens in the S (synthesis) phase?
DNA is replicated
What happens in G2 (second growth) stage?
when organelles grow and divide and energy stores are increased
What happens in nuclear division?
the nucleus divides either into two or four
What happens in cell division?
when the whole cell divides into two or four
What is cancer?
a group of diseases caused by a growth disorder of cells
How do cancer drugs disrupt the fell cycle?
- preventing DNA from replicating e.g. cisplatin
2. inhibiting the metaphase stage of mitosis by interfering with spindle formation e.g. vinca alkaloids
Why are cancer drugs more effective killing cancer cells than normal body cells (apart from hair)
- The drugs are more effective against rapidly dividing cells
- as cancer cells divide at a fast rate, they are damaged to a greater degree than normal cells
- hair cells divide rapidly also, which are targeted by cancer drugs which explains the hair loss in cancer patients-
Descibe how the quantity of DNA in cells is increased during phase S.
- DNA unravels to form two single stranded DNA molecules;
- these attract complementary nucleotides;
- these join to sense strands forming daughter DNA.
- Under the influence of DNA polymerase;
- bases join by hydrogen bonds between complementary pairs
- and adjacent sugars join by phosphate bridges;
How is the quantity of DNA returned?
- chromatids separate to poles;
- during anaphase;
- nuclear membranes then reform around two daughter nuclei;
- each containing the diploid number of chromosomes;
What is male chromosomes in terms of X AND Y’S
XY
What is female chromosomes in terms of X AND Y’S
XX
Explain how you could have recognised which cells were in interphase when looking at tissue samples.
- no visible chromosomes
2. visible nucleus
