Cell Replication

Question 1

What are the 4 phases of mitosis

Answer 1

Prophase: DNA condenses, centrioles/asters assemble the mitotic spindle machinery; nuclear envelope breaks down

Metaphase: with help of mitotic spindle machinery, sister chromatids align at metaphase plate (center of cell)

Anaphase: Sister chromatids are pulled apart and separate; cytokinesis beings- cleavage furrow starts to form and cytokinesis begins: actin begins to cinch the cytoplasm like a belt.

Telophase: reverse of mitotic prophase: reforms nuclear envelope, mitotic spindle machinery breaks down, DNA decondense. cytokinesis finishes.

Question 2

what are the 3 phases of interphase

Answer 2

G1: cell grows in size, protein synthesis, and organelles are duplicated
S: DNA replicates
G2: DNA is revised for possible mutation

Question 3

what is the phase where the cell is not actively dividing?

Answer 3

G0

i.e. most neurons are in this phase

Question 4

What are the 4 defining characteristics of cancer

Answer 4

• results from mutations in key genes that are responsible for regulating the cell cycle
• starts from cells with altered DNA
• cells grow and divide without any control
• have ability to spread to surrounding tissues (metastasize)

Question 5

What are proto-oncogenes

Answer 5

refers to the genes normally present in the cell that code for proteins that regulate the cell cycle.
these proto-oncogenes are only activated when the cell is undergoing interphase and mitosis i.e. fetal development, whole body growth, and wound healing
for normal growth/healing, these proto-oncogenes will not be expressed in a normal cell

Question 6

a proto-oncogene that is permanently active is now considered a(n) ____

Answer 6

oncogene
this results from a mutation in the gene that code for proto-oncogenes, but now these genes are constantly turned on and thus these oncogenes are always being expressed and always undergoing the cell cycle
-there is a fail safe for these oncogenes in G2 phase, as the tumor suppressor gene in the G2 phase checks for mutations, which will normally catch the oncogene mutation

Question 7

tumor suppressor genes code for proteins that slow down cell ____

Answer 7

growth

Question 8

If DNA is found damaged, tumor suppressor genes initiate ______ processes

Answer 8

DNA repair

Question 9

If damaged DNA is not repairable, then tumor suppressor proteins trigger _____

Answer 9

apoptosis

Question 10

What are caspases

Answer 10

these are proteases that initiate and carry out apoptosis

Question 11

What’s the difference between extracellular death signals and intracellular death signals?

Answer 11

extracellular death signals refer to those signals that come from outside the cell that trigger that cell to undergo apoptosis i.e. an immune cell triggers another cell to undergo apoptosis

intracellular death signal refer to those signals that come from inside the cell to trigger apoptosis i.e. tumor suppressor proteins

Question 12

in the process of apoptosis, what causes the initiator caspases to clump up together, leading to their activation?

Answer 12

when the cell shrinks, the initiator caspases will clump together

Question 13

what activates the effector caspases?

Answer 13

the activation of initiator caspases with activate the effector caspases

Question 14

what is the role of effector caspases?

Answer 14

they literally eat the cell from the inside out in the process of apoptosis

Question 15

oncogenes is a ___1__ of function mutation, whereas the mutation of tumor suppressor genes causes a __2___ of function mutation

Answer 15

1) gain of function

2) loss of function