chapter 4: the cell cycle

Question 1

what is binary fission?

Answer 1

the method of cell reproduction/replication of prokaryotes. it is a form of asexual reproduction

Question 2

first step of binary fission

Answer 2

1. replication
   - the coiled chromosome uncoils and duplicates
   - plasmids duplicate
   - any other structures such as ribosomes duplicate

Question 3

second step of binary fission

Answer 3

elongation
- the cell grows long enough to divide in to two separate cells

Question 4

third step of binary fission

Answer 4

separation
- also called cytokinesis
- the chromosomes move away from each other
- the cell pinches into 2
- creates a new cell wall (if applicable) called the septum and membrane

Question 5

how is variation found in binary fission?

Answer 5

through mutation

Question 6

how do you figure out the how many daughter cells there will be once after time?

Answer 6

Number of divisions = time / how long it takes for a division
2 to the power of no. of divisions

Question 7

what is the cell cycle?

Answer 7

the eukaryotic cell cycle is the replication of eukaryotic cells

Question 8

what are the phases of the cell cycle?

Answer 8

interphase, mitosis and cytokinesis

Question 9

what is phase one of interphase?

Answer 9

G1 phase is when the cell gets bigger by increasing the amount of cytosol. it makes copies of its organelles, and makes molecules (such as protein) it will need later on.

Question 10

what is phase 2 of interphase?

Answer 10

the S phase - DNA replicates, turning the chromosome into 2 identical sister chromatids. if they are held together by a centromere, they are sill considered a chromosome.

Question 11

what is phase 3 of interphase?

Answer 11

G2 phase - increases in cytosol more as well synthesis more proteins in preparation for mitosis

Question 12

what is mitosis?

Answer 12

Mitosis - occurs once the DNA replication is complete and the cells have passed all checkpoints. Mitosis has 4 stages, Prophase, Metaphase, Anaphase and Telophase.

Question 13

what is prophase?

Answer 13

prophase - the nuclear envelope breaks down, DNA as chromatins condenses into chromosomes, and spindles form
PECS

Question 14

what is metaphase?

Answer 14

metaphase - the chromosomes position on the equator of the cell, microtubules bind to the sister chromatids, and the spindles extend from the centriols

Question 15

what is anaphase?

Answer 15

anaphase - separation of sister chromatids and spindles shorten to pull them to the poles of the cell

Question 16

what is telophase?

Answer 16

telophase - uncoiling of chromosomes, nuclear envelope reforms and the spindles disappear

Question 17

what is cytokinesis?

Answer 17

the final stage of the cell cycle where the cell separates. a nucleus forms on each side of the cell, cytosol and other organelles surround the nucleus.

Question 18

cytokinesis in animals

Answer 18

The cell membrane either furrows and then splits

Question 19

cytokinesis in plants

Answer 19

cellulose is deposited into a cell plate and then it separates.

Question 20

what is the G1 checkpoint?

Answer 20

occurs right after the G1 phase.
- grown to the right size
- has synthesised enough protein for DNA replication
- checks if DNA has been damaged
- enough oxygen and nutrients
it looks at is if the environment is favourable to keep going.

Question 21

what is the G2 checkpoint?

Answer 21

ensures that DNA has replicated properly in the S phase, and that the cell has enough resources for mitosis.

Question 22

what is the metaphase checkpoint (spindle assembly)?

Answer 22

In the metaphase checkpoint, the cell checks the formation of the spindle fibres. If the chromosomes are lined up in the correct location, the cell proceeds to anaphase.

Question 23

what happens if a cell fails a checkpoint?

Answer 23

goes into apoptosis

Question 24

what is apoptosis?

Answer 24

regulated/programmed cell death. if it malfunctions there may be deviant cell behaviour.
- helps maintain cell numbers
- defence against damaged/dangerous cells

Question 25

what is necrosis?

Answer 25

necrosis is unplanned cell death. it is different from apoptosis as it is not regulate and sudden. it is when cells suffer trauma to the point they die prematurely in comparison to receiving death signals to die

Question 26

steps of apoptosis

Answer 26

apoptosis begins with the activation of the death signals, either intrinsic (mitochondrial) or extrinsic (death receptor)