The Cell Cycle & Cancer

Question 1

What are the four phases of the Cell Cycle? Which of these are considered Interphase?

Answer 1

G1, S, G2, M
(G1, S, G2 are considered interphase)

Question 2

What are the 2 phases within M phase? What are their functions?

Answer 2

Mitosis: division of the nucleus
Cytokinesis: division of the cytoplasm

Question 3

What are the functions of the different phases within interphase?

Answer 3

G1: regular cellular activity

S: copying (synthesizing) DNA

G2: regular cellular activity + making proteins for replication

Question 4

What are chromosomes? How many do humans have?

Answer 4

Single strand of DNA
Humans have 46 chromosomes

Question 5

How are sister chromatids created?

Answer 5

During S phase chromosomes are copied and paired together to form sibling chromatids.

Question 6

What is centromere? Where are they located?

Answer 6

The centromere is the site of separation during M phase. (it helps cells divide) Sibling chromatids are joined at the centromere.

Question 7

T/F sibling chromatids are considered a chromosome?

Answer 7

True

Question 8

What are telomeres?

Answer 8

Telomeres are repetitive ends of chromatids or chromosomes. Each time a cell replicates it loses a bit of telomere, once telomere is lost the cell fails to divide.

Question 9

What are telomerase?

Answer 9

Telomerases are enzymes that add more telomeres to chromosomes so that the cells can continue to divide.
(present in stem cells)

Question 10

Why do cells need to divide?

Answer 10

Growth
Repair
Replenishment

Question 11

What sub-phases are within M phase?

Answer 11

Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis

Question 12

What happens in Prophase?

Answer 12

• Spindle fiber formation. (made of microtubules)
• Centromosomes (organizing proteins) move to opposite sides of the cell.
• Chromatin condenses.

Question 13

What is chromatin made up of? What are there functions?

Answer 13

Histone: a protein that binds DNA
Nucleosome: DNA would twine around histone.

Question 14

What happens in Prometaphase?

Answer 14

• The nuclear membrane breaks down 
• Spindle fibers begin to attach to the centromere of chromosomes 
  - Kinetochore: proteins at centromere that attach microtubules
• Tugging begins from each centrosome

Question 15

What happens in Metaphase?

Answer 15

Chromosomes align along metaphase plate (in the middle of the cell)

Question 16

What happens in Anaphase?

Answer 16

Chromatids are pulled apart towards opposite sides of the cell

Question 17

What happens in Telophase?

Answer 17

Spindle fibers break down. Nuclear membrane reforms.
(2 separate nuclear membranes on each side of the cell)

Question 18

How is cytokinesis different between animal and plant cells?

Answer 18

Animal cells: cleavage furrow 
Contractile ring made of proteins ACTIN & MYOSIN 

Plant cells: new cell plate formed 
Vesicles deliver new cell wall material to the middle of the cell

Question 19

What are some characteristics that define cancer?

Answer 19

• Uncontrolled growth
• Infinite number of divisions
• Less prone to apoptosis (a process to keep certain cells from taking over): Intention death of cells
• Genetically unstable: Different numbers of chromosomes or chromosomes being in incorrect places.
• Metastis: when cancer cells invade & colonize distant tissues

Question 20

What are the different types of tumors, how are they different?

Answer 20

Benign: Uncontrolled cell division 
Not invasive => cells don’t migrate and colonize 

Malignant (cancer): Uncontrolled cell division 
Migrate and invade 

(Surgery alone can only cure benign tumors)

Question 21

What are the different types of cancer genes and their functions?

Answer 21

Proto-oncogenes: Stimulate cell division
- Mutation can turn this gene into an oncogene (gene never turns off)

Tumor Suppressor Genes: Inhibit cell division
- Mutation can turn this gene off

Genome Stability Genes: DNA repair genes
- Mutation can turn this gene off

Question 22

T/F You only need one mutation to create cancer?

Answer 22

False, you need multiple mutations to create cancer.