Cell division, Cell diversity and cell differentiation

Question 1

define cytokenisis

Answer 1

cytoplasmic division following nuclear division, resulting in two new daughter cells

Question 2

define interphase

Answer 2

phase of cell cycle where the cell is not dividing; it is subdivided into growth and synthesis phases

Question 3

define mitosis

Answer 3

type of nuclear division that produces daughter cells genetically identical to each other and to the parent cell

Question 4

what are the two main checkpoints of cell division

Answer 4

the G1 and G2

Question 5

what is the purpose of the checkpoints

Answer 5

• to prevent uncontrolled division but could lead to tumours
• to detect and repair damage to DNA

Question 6

as the molecular events that control the cell cycle happen in a specific sequence, what do they also ensure

Answer 6

• the cycle cannot be reversed
• the DNA is only duplicated once during each cell cycle

Question 7

describe binary fission

Answer 7

• cell grows to its limit of size and splits into 2
• before cell divides DNA is replicated
• 2 new loops of DNA are pulled to opposite ends of the cell
• cell wall forms which begins to separate the bacterial cell

Question 8

describe the M phase

Answer 8

• a checkpoint chemical triggers condensation of chromatin
• halfway through the cycle the metaphase checkpoint ensures that the cell is read to complete mitosis

Question 9

describe the events within the M phase

Answer 9

• cell growth stops
• nuclear division consisting of stages prophase, metaphase, anaphase, and telophase
• cytokinesis

Question 10

describe the G0 phase

Answer 10

• a resting phase triggered during early G1 at the restriction point by a checkpoint chemical

Question 11

describe the events during the G0 phase

Answer 11

• in this phase cells may undergo apoptosis (programmed cell death), differentiation
• some types of cells remain in this phase for a very long time or indefinitely

Question 12

describe the G1 phase (the growth phase)

Answer 12

a G1 checkpoint control mechanism ensures that the cell is ready to enter the S phase and begin DNA synthesis

Question 13

describe what happens during the G1 phase

Answer 13

• cells grow and increase in size
• transcription of genes to make RNA occurs
• organelles duplicate
• biosynthesis including making the enzymes needed for DNA replication in the S phase
• the P53 gene helps control this phase (tumour supressor)

Question 14

describe the S phase

Answer 14

because the chromosomes are unwound and the DNA is diffuse, every molecule of DNA is replicated

Question 15

describe what happens during the S phase

Answer 15

• once the cell has entered this phase it is committed to completing the cell cycle
• DNA replicates
• when all chromosomes are duplicated each one consists of a par of identical sister chromatids
• the phase is rapid which reduces the chances of spontaneous mutations happening

Question 16

describe the G2 phase

Answer 16

special chemicals ensure that the cell is ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and information of the spindle

Question 17

describe what happens during the G2 phase

Answer 17

the cells grow