The Cell Cycle And Mitosis

Question 1

What is the cell cycle

Answer 1

The regulated sequence of events that occurs between one cell division and the next

Question 2

What are the three phases of the cell cycle

Answer 2

-interphase
-nuclear division(mitosis)
-cell division(cytokinesis)

Question 3

What is the length of the cell cycle dependent on

Answer 3

Dependent on environmental conditions, the cell type and the organism

Question 4

What are cyclins

Answer 4

The chemical signals that trigger the movement from one cell cycle phase to another

Question 5

What are the three phases of interphase

Answer 5

-Gap 1(G1)
-synthesis
-gap 2 (G2)

Question 6

What happens during gap 1 in interphase

Answer 6

Cell makes more organelles and proteins ready for cell division

Question 7

What happens during synthesis phase of interphase

Answer 7

DNA replicates, the chromosome becomes two sister(identical) chromatids joined together by a centromere

Question 8

What happens during gap 2 phase of interphase

Answer 8

-cell keeps growing
-new DNA that has been synthesised is checked and any errors are usually repaired
-other preparations for cell division are made eg production of tubulin protein which is used to make microtubules for the mitotic spindle

Question 9

What are sister chromatids

Answer 9

Identical chromatids joined together in the same chromosome by a centromere

Question 10

What are the four phases of mitosis phase and how to remember stages

Answer 10

Prophase where the cell Prepares to divide
Metaphase where the chromosomes align along the Middle
Anaphase where the chromosomes move Away from each other
Telophase where Two nuclei reform

Question 11

What happens during prophase

Answer 11

-chromosomes condense and are now visible when stained
-the chromosomes consist of two identical sister chromatids joined together at the centromere with each containing one DNA molecule
-the two centrosomes(replicated in G2) move towards opposite poles
-spindle fibres(protein microtubules) begin to extend from the centrosomes(which consist of two centrioles in animal cells)
-nuclear envelope breaks down into small vesicles

Question 12

What happens during metaphase

Answer 12

-centrosomes reach opposite poles
-spindle fibres continue to extend from centrosomes
-chromosomes line up at the equator of the spindle so are equidistant to the two centrosome poles
-spindle fibres reach the chromosomes and attach to the centromeres
-each sister chromatid is attached to a spindle fibre originating from opposite poles

Question 13

What are spindle fibres

Answer 13

Protein microtubules that divide the sister chromatids and extend from centrosomes

Question 14

What happens during anaphase

Answer 14

-sister chromatids separate at the centromere and the centromere divides in two
-spindle fibres begin to shorten
-the separated sister chromatids (now called chromosomes) are pulled to opposite poles by spindle fibres and are pulled centromere first towards the centrosomes

Question 15

What happens in telophase

Answer 15

-chromosomes arrive at opposite poles and begin to de-condense
-nuclear envelopes begin to reform around each set of chromosomes
-spindle fibres break down

Question 16

Why during interphase are the individual chromosomes unravelled

Answer 16

To allow access to the genetic material so new proteins can be synthesised

Question 17

Why do chromosomes condense during prophase

Answer 17

To make them easier to separate and so each daughter cell receives the correct number and type of chromosome, also protects the DNA from damage

Question 18

What happens during cytokinesis in animal cells

Answer 18

Final stage and is the separation of the cytoplasm to form two new cells, ring of proteins filaments bound to the inside surface of the cell membrane contracts until cell divides into two new cells

Question 19

What happens during cytokinesis in plant cells

Answer 19

Synthesis of a new plate(precursor to new cell wall) between the two new cells