1.6 Mitosis

Question 1

Tumor

Answer 1

abnormal cell growth resulting from uncontrolled cell division, can occur in any tissue or organ

Question 2

Mutagen

Answer 2

agent that changes DNA

• Radiation
• DNA interacting with reactive metals(arsenic)
• Viruses, certain bacteria and mobile genetic elements
• mutagens that lead to the formation of cancer are further classified as carcinogens.

Question 3

what are cyclins

Answer 3

a family of regulatory proteins that control the progression of the cell cycle

Question 4

how do cyclins control the cell cycle

Answer 4

1. Cyclins bind to enzymes called cyclin-dependent Kinesis(CDK)
2. The complex will then bind to a target protein and modify it via phosphorylation
3. the phosphorylated protein will trigger a specific event within the cell cycle
4. After this has occurred the cyclin will degrade and the CDK is rendered inactive again.

Question 5

Prophase

Answer 5

DNA supercoils and chromosomes condense
Chromosomes are comprised of genetically identical sister chromatids(joined at a centromere)
Paired centrosomes move to the opposite poles of the cell. form microtubule and spindle fires.
Nuclear membrane breaks down an dissolves.

Question 6

Oncogene

Answer 6

gene with potential to become cancerous.

Question 7

What are the stages of Interphase

Answer 7

G1- First immediate gap stage in which the cell grows and prepares for DNA replication
S- Synthesis stage in which DNA is replicated
G2- Second intermediate gap stage in which the cell finishes growing and prepares for cell division

Question 8

What is the M phase and what are the two distinct stages in it?

Answer 8

the period of the cell cycle in which the cell and contents divide to create two genetically identical daughter cells. Composed of mitosis and cytokinesis.

Question 9

Mitosis

Answer 9

Where DNA is separated into two identical daughter nuclei.

Question 10

Cytokinesis

Answer 10

cytoplasmic division, whereby cellular contents are segregated and the cell splits into two.

Question 11

What are the events that need to occur in interphase to prepare the cell for successful division?

Answer 11

DNA replication- DNA is copied during the S phase of interphase
Organelle duplication- Organelles must be duplicated for twin daughter cells
Cell growth- Cytoplasmic volume must increase prior to division
Transcription/translation- Key proteins and enzymes must be synthesised
Obtain nutrients- Vital cellular materials must be present before division
Respiration(cellular)- ATP production is needed to drive the division process.

Question 12

What is chromatin

Answer 12

a level of DNA packaging with the DNA helix wrapped around the histones to form nucleosomes, these are then coiled together to form a chromatin fibre.

Question 13

what happens to chromosomes before division? why is this beneficial?

Answer 13

DNA is temporarily packaged into a tightly wound and condensed chromosome prior to division(supercoiling). In this condensed form, the DNA is able to be easily segregated however is inaccessible to transcriptional machinery.
DNA is organized as chromosomes during the process of mitosis(condense in prophase, decondense in telophase)

Question 14

What is a chromosome

Answer 14

the condensed form of DNA which is visible during mitosis

Question 15

What does the cell look like during interphase

Answer 15

DNA is present as uncondensed chromatin
DNA is contained within a clearly defined nucleus
Centrosomes and other organelles have been duplicated
Cell is enlarges in preparation for division

Question 16

Metaphase

Answer 16

• Microtubule spindle fires from both centrosomes connect to the centromere of each chromosome
• Microtubule depolymerisation causes spindle fibres to shorten in length and contract
• This causes chromosomes to align along the centre of the cell(equatorial plane or metaphase plate)

Question 17

Anaphase

Answer 17

Continued contraction of the spindle fibres causes genetically identical sister chromatids to separate.
Once the chromatids separate, they are each considered an individual chromosome in their own right
The genetically identical chromosomes move to the the opposite poles of the cell.

Question 18

Telophase

Answer 18

Once the two chromosome sets arrive at the poles, spindle fires dissolve
Chromosomes decondense
Nuclear membranes reform around each chromosome set
Cytokinesis occurs concurrently, splitting the cell into two.

Question 19

why is cyclin concentration important

Answer 19

cyclin levels will peak when their target protein is required for function and remain at lower levels at all other times

Question 20

Metastasis

Answer 20

the spread of cancer from one location(primary tumor) to another, forming a secondary tumor