Cell Cycle

Question 1

Why do cells divide?

Answer 1

to grow, heal or reproduce an organism

Question 2

Explain Daughter and Parent cells

Answer 2

the parent cells are the cells undergoing cell division

the daughter cell is the resulting cells from the cell division

Question 3

Define Haploid

Answer 3

Cells that contain only one set of chromosomes

Question 4

Define Diploid

Answer 4

cells that contain two sets of chromosomes

Question 5

What are some organisms with more than two sets of chromosomes?

Answer 5

plants and fungi

4 sets —> tetraploid

8 sets —> octoploid

Question 6

Describe Mitosis and the four steps

Answer 6

the process of nuclear replication
(not cell division)

required for any eukaryotic cell prior to cell division

consists of four steps :
Prophase, Metaphase, Anaphase, Telophase

Question 7

Describe Prophase

Answer 7

the preparation stage for nuclear division

the chromosomes condense out of the nucleoplasm becoming visible under a microscope

Question 8

Describe the chromosomes during prophase

Answer 8

The chromosomes during prophase consist of two Chromatids joined together

Question 9

What are Chromatids?

Answer 9

strand of DNA and attached proteins

the nuclear membrane dissolves during prophase, exposing the chromosomes

Question 10

What is a Centromere?

Answer 10

the point where chromosomes join

Question 11

Explain how the centrioles work in prophase

Answer 11

Centrioles (two organelles) move to opposite ends of the cytoplasm and act as attachment sites for Spindle Fibres (grappling hooks)

centrioles are only found in animal cells

Question 12

Where do spindle fibres attach?

Answer 12

Spindle fibres attach to the centromeres of each chromosome pair

(joining point of chromatids)

Question 13

Describe Metaphase

Answer 13

the second stage of mitosis where chromatids prepare to be separated and divided

chromosomes meet in the center of the cell —> Equator / Equatorial Plane

Question 14

Describe Anaphase

Answer 14

the third stage of mitosis where genetic information is divided up and sorted to opposite ends

centromeres detach in anaphase, resulting in single chromosomes (separated pairs)

the spindle fibres work w the centrioles to make sure that each end of the cell receives an equal number of chromosomes

they also make sure that each end of the cell contains one of each chromosome

Question 15

Describe Telophase

Answer 15

the final stage of nuclear division, where new nuclei are formed in preparation for cell division

the separated chromosomes dissolve back into the cytoplasm

nuclear membranes begin to form around the chromosomes at each end of the cell, resulting in new nuclei

Question 16

When is it clear that Mitosis is complete?

Answer 16

During Telophase, once the nuclei have been reformed

Question 17

Describe Cytokinesis and when does it occur?

Answer 17

the movement of cytoplasm and organelles

following mitosis, cytoplasm and other organelles divide and move to opposite ends of the cell

part of the M stage

Question 18

What causes the separation of the newly formed daughter cells?

Answer 18

A Contractile Ring causes the cell membrane to contract and narrow at the centre

once the ring closes completely, it pinches at the centre, resulting in two daughter cells

Question 19

What is the M phase?

Answer 19

the M phase (cell division) is just one stage of the cell cycle

(m for mitosis)

The M stage occurs after Interphase (G1, S, G2)

contains both cytokinesis and mitosis

Question 20

Describe Interphase

Answer 20

the three stages between cell division

(inter —> interval between cell division)

G1, S, G2

Question 21

Describe the G1 phase

Answer 21

the first stage in interphase which stands for 1st growth

the cell grows and performs it’s normal function

longest stage of the cell cycle

Question 22

Describe S stage

Answer 22

the second stage of interphase, the S stands for synthesis

synthesis in the S stage refers to DNA replication (synthesizing new DNA)

S stage is the cells first preparation for mitosis by doubling the amount of DNA

Question 23

Describe the amount of DNA in a cell during S stage

Answer 23

the amount of DNA in the cell doubles during S stage, from 46 chromatids to 92 chromatids

still diploid because they are paired through centromeres

92 chromatids, 46 chromosomes

Question 24

Describe the G2 stage

Answer 24

the final stage of interphase, 2nd growth

stage where the cell grow until it is large enough for cell division

a lot of protein synthesis, specifically the synthesis of spindle fibre proteins

Question 25

What is at the end of each growth stage?

Answer 25

A checkpoint

Question 26

Describe the role of G1 Checkpoint Proteins

Answer 26

they ensure that cells have a sufficient size and amount of nutrients

in order to exit G1 cells and begin DNA replication, the cell must receive a signal from outside the cell, which acts as a clearance code

once the g1 checkpoint is cleared, the cell is committed to DNA Replication, no going back

Question 27

Describe the role of G2 Checkpoint Proteins

Answer 27

they ensure that the cells don’t enter M phase (mitosis) until a DNA damage inspection has been done

this inspection is not perfect and sometimes damaged DNA can get through the G2 checkpoint

the replication of damaged DNA can be dangerous to the cell and organism

Question 28

What are Somatic cells?

Answer 28

Cells that follow a diploid cell cycle

(2 sets of chromosomes in humans —> 46)

all body cells that aren’t used for reproduction

they are responsible for normal functioning of the individual

Question 29

Describe Sex Cells, what are they called and how are the reproduced?

Answer 29

haploid cells that involve reproduction

(contain one set of chromosomes —> 23)

also called Gametes

reproduced through the process of Meiosis

Question 30

Describe Meiosis

Answer 30

similar to mitosis, but contains a second nuclear division

DNA is not replicated prior to the second division of meiosis

The two divisions result in four daughter cells each with a haploid set of chromosomes

Question 31

Describe Genetic Recombination

Answer 31

prior to the second cell division, the cells undergo genetic recombination

it is the process where sister chromosomes exchange DNA to increase genetic variation

Question 32

Describe Tumours

Answer 32

cells that grow at an uncontrollable rate

*cell division must be regulated so that cells don’t divide uncontrollably

Question 33

Describe Benign Tumours

Answer 33

tumours that are located

this means that they don’t infringe upon surrounding tissues or spread throughout the body

Question 34

Describe Malignant Tumours

Answer 34

Tumours that invade surrounding tissue or spread throughout the body

the common name for malignant tumours is cancer

Question 35

What is Metastasis?

Answer 35

the spread of malignant cells throughout the body, resulting in tumors

Question 36

What causes cancer?

Answer 36

Genetic Changes to a cell

these genetic changes result in the changes to the cell cycle, resulting in too much cell division

Question 37

Describe Oncogenes

Answer 37

A gene that has the potential to make a cell cancerous

oncogenes start as genes responsible for regulating cell division,

these cells have the potential to result in uncontrollable growth and cell division

Question 38

What are the 4 different factors that can trigger Oncogenes?

Answer 38

1. Mutations during DNA Replication
2. Mutations due to a Carcinogen (substance that causes cancer)
3. Mutation or damage due to Radiation (UV or X-RAY)
4. DNA inserted by a Virus (DNA Viruses, like HPV, insert into the DNA)

if they insert into the middle of an oncogenes it results in Cancer