UNIT 2: The cell cycle

Question 1

cell continuity

Answer 1

cells that arise from cells of the same type.

living organisms maintain cell continuity by mitosis and cell division

Question 2

chromatin

Answer 2

elongated DNA

Question 3

chromosomes

Answer 3

composed of DNA and protein.

arranged into homologous pairs - pairs of chromosomes that contain genes that control the same characteristics.

Question 4

haploid

Answer 4

one set of chromosomes

in humans, the haploid number is 23

Question 5

diploid

Answer 5

2 sets of chromosomes

in humans the diploid number is 46 - arranged into 23 pairs

Question 6

the cell cycle

Answer 6

The changes that take place in a cell during the period between one cell division and the next.
occurs under three distinct stages:
1. interphase
2. mitosis
3. cell division

Question 7

interphase

Answer 7

• the stage where a cell is not dividing and a cell spends the vast majority of its time in this stage.
• chromosomes are elongated and the cell goes about its daily functions.
• towards the end of interphase the cell organelles and DNA are replicated.

Question 8

end of interphase

Answer 8

the DNA is replicated and condenses into duplicated chromosomes which are held together by centrometres.

Question 9

mitosis

Answer 9

the nuclear division in which one nucleus divides to form 2nuclei, each containing the same number of chromosomes with identical genes.
stage 1: prophase
stage 2: metaphase
stage 3: anaphase
stage 4: telophase

Question 10

prophase

Answer 10

the nuclear membrane begins to disappear and spindle fibres begin to appear from the centrioles.

Question 11

metaphase

Answer 11

the replicated chromosomes line up along the equator of the cell held in place by spindle fibres.

Question 12

anaphase

Answer 12

the spindle fibres begin to contract pulling one chromosome from each pair to each pole.

Question 13

telophase

Answer 13

the chromosomes at each pole begin to unravel and lengthen, spindle fibres disappear, and nuclear membranes reform at each pole.

Question 14

cell division (cytokinesis)

Answer 14

cell division occurs immediately after mitosis and involves formation of cleavage furrow (in animal cells) or cell plate (in plant cells) prior to cell splitting

Question 15

cell division - meiosis

Answer 15

meiosis is nuclear division in which the four daughter nuclei contain half the chromosomes number of the parent nucleus

Question 16

cancer

Answer 16

a disease whereby a cell loses its ability to control both the rate of mitosis and cell division.
- mitosis is normally carefully controlled but when it is out of control it can result in cancer.
- benign cancer involves cells that divide out of control for a limited period of time and do not spread.
- malignant cancer involves cells that divide rapidly uncontrollably and spread and invade other tissues - destroying that tissue in the process.
- anything that has the potential to cause cancer = carcinogen - destroys DNA
-

Question 17

carcinogens

Answer 17

UV light- damages DNA of skin cells

cigarette smoke - damages the DNA of cells lining the mouth, airways and lungs.

Question 18

Gene

Answer 18

A section of DNA that contains the instructions for the formation of a protein

Question 19

Centromere

Answer 19

A point at which the chromosomes are attached in a double stranded chromosome