Eukaryotic cell cycle

Question 1

Which scientist should be credited for cell theory?

Answer 1

Rudolf Virchow

Question 2

What is cell theory of 1855?

Answer 2

Rudolf Virchow,

All living organisms are made up of cells.

Cells are the basic structural and organizational units of all organisms.

All cells come from pre-existing cells ‘Every cell from a cell’.

All cells in multicellular organisms come from a single cell

Question 3

What are the functions of cell division?

Answer 3

Reproduction- divides to form two cells, each an individual organism.

Growth and development- helps develop cell to form multicellular organism.

Question 4

Give an example of multicellular organisms cell division for repairing and renewing?

Answer 4

Dividing bone marrow cells continuously make new blood cells. In a human adult 2 million stem cells divide every second to give constant number of red blood cells in the body.

Question 5

What is the period between one M phase and the next?

Answer 5

interphase.

Question 6

What is the main principle of mitosis?

Answer 6

When the nucleus divides.

Question 7

What is the main principle of cytokinesis?

Answer 7

when the cell itself splits in two

Question 8

What do mitosis and cytokinesis make up the cell cycle, what is it called?

Answer 8

The M phase

Question 9

How long does the M phase last?

Answer 9

an hour, whole cell cycle lasts 24 hours. 1/24

Question 10

What does S phase do and stand for?

Answer 10

Synthesis, the cell replicates its DNA

Question 11

What are the three phases in the cell cycle?

Answer 11

G1 phase
S phase
G2 phase

Question 12

What happens during the gap phases of the cell cycle?

Answer 12

The cell monitors both its internal state and external environment to ensure that conditions are suitable for reproduction and that preparations are complete before the cell commits to the major upheavals of S phase (which follows G1) and mitosis (following G2).

Question 13

What is a quiescent state in the cell cycle?

Answer 13

Metabolically active but not dividing.

Question 14

What happens in G0 phase?

Answer 14

Cells have the potential to divide if stimulated by growth factors.

Question 15

Give an example of a cell that has as an “abbreviated” cell cycle?

Answer 15

Egg of the frog Xenopus- after fertilisation, it divides rapidly to partition egg into many smaller cells.

Question 16

How does an abbreviated cell cycle work?

Answer 16

Rapid cell cycles consist of repeated S and M phases, with little or no G1 or G2 phases between them.

No new gene transcription, no new cell growth, cells divide and grow smaller with each division. Only DNA is replicated.

Question 17

What type of protein is DNA associated with?

Answer 17

Histone proteins.

Question 18

The DNA-protein complex(chromatin) is organised into what form?

Answer 18

Long, thin fibre.

Question 19

What happens before cell division and after DNA duplication?

Answer 19

Chromatin condenses becoming densely coiled and folded. Making chromosomes shorter and thick (making it visible to a light microscope).

Question 20

What does each duplicated chromosome have, containing what?

Answer 20

Duplicated chromosomes have two sister chromatids each containing identical copies of chromosome’s DNA.

Question 21

Where are telomeres found ?

Answer 21

At each of the two ends of a chromosome

Question 22

What do telomeres contain?

Answer 22

Contain repeated nucleotide sequences

Question 23

What do telomeres do?

Answer 23

PROTECTIVE

• Telomeric DNA protects the organism’s genes from being eroded through successive rounds of DNA replication

Question 24

What is the role of cohesins?

Answer 24

They tie together the two adjacent sister chromatids in each replicated chromosome.

This is essential for chromosome segregation- cohesin rings.

Question 25

What occurs before the Mitotic(M) phase of the eukaryotic cell cycle?

Answer 25

Cell growth by gene transcription and protein synthesis producing e.g. proteins and cytoplasmic organelles Cell increases in size Chromosomes are duplicated only during S-phase Centrosome duplication also occurs in interphase. **KEY IS THAT IT IS NOT RESTING.

Question 26

Why does the centrosome of an interphase cell duplicate?

Answer 26

To form the two poles of a mitotic spindle. (occurs in early M phase)

Question 27

What two processes occur in M phase?

Answer 27

mitosis(nuclear division) and cytokinesis(cytoplasmic division)

Question 28

How long does the M phase take in the body?

Answer 28

1 hour

Question 29

What is the aim of the M phase?

Answer 29

Accurately segregate the chromosomes duplicated in the preceding S phase, so each new daughter cell receives an identical copy of the genome

Question 30

What happens in prophase in depth?

Answer 30

Duplicated chromosomes, each consisting of two close sister chromatids are condensed. Kinetochore formed. Mitotic spindle forms, extending from the two centrosomes. Nucleolus disintegrates and transcription ceases.

Question 31

What does the kinetochore do(that is formed in prophase)?

Answer 31

Attaches chromosomes to the mitotic spindle, it recognises a special DNA sequence at the centromere, at this centromere it contains a specialised protein called a CENP-A to recruit addition proteins to form kinetochore complex.

Question 32

What happens at prometaphase in M phase?

Answer 32

- Breakdown of nuclear envelope -Microtubules become kinetochore microtubules through invasion of the nuclear area.

Question 33

What happens in metaphase(in the M phase)

Answer 33

Mitotic spindle fully formed. Chromosomes aligned at the equator of spindle(equidistant) Centrosomes of the chromosomes are all on the metaphase. Kinetochore microtubules on sister chromatids attach to opposite poles of the spindle.