Lecture 10: cell division and cancer

Question 1

why do somatic cells divide

Answer 1

growth and development, tissue renewal

Question 2

What somatic cells don’t divide after maturity

Answer 2

muscle, nerve, brain cells. They just stay in interphase.

Question 3

What are the 4 parts of the eukaryotic cell cycle

Answer 3

G (growth/gap) 1 , S, G2 and Mitotic (M) phase = mitosis + cytokinesis.

Question 4

describe G1; whats happening and duration

Answer 4

cell metabolically active. duplication of organelles and cytostolic components. centrosome replication begins.

Question 5

Where can nondividing cells exit the Cell cycle for G 0

Answer 5

from G1

Question 6

describe S phase

Answer 6

Synthesis for DNA where DNA replication occurs by DNA polymerase, strands are separated at the H bonds holding nucleotides together, new strand of DNA synthesised opposite each of the old strands.

Question 7

describe G2

Answer 7

Checks for correct DNA synthesis, preparing for Mitotic phase (synthesis of the proteins and enzymes required, gathering of reactants) replication of centrosomes is completed

Question 8

What are the 5 steps of Mitosis in order

Answer 8

Prophase, metaphase, anaphase, telophase

Question 9

What happens in prophase

Answer 9

Mitotic spindle forming, chromatin condensing to chromosomes. PM: The nuclear envelope breaks, chromosomes attach to microtubules

Question 10

What happens in metaphase

Answer 10

Chromosomes line up in a metaphase plate

Question 11

What happens in anaphase

Answer 11

sister chromatids separate (at the centromere) and over as the new chromosomes to pole

Question 12

What happens in telophase

Answer 12

the cell nuclei form, spindles disappear, cleavage furrow

Question 13

Cytokinesis is the process of

Answer 13

partitioning the cytoplasm into two daughter cells

Question 14

Chromosomes are

Answer 14

two identical chromatids held together by a centromere.

Question 15

we have 23 chromosomes from mum and 23 chromosomes from dad which mean that we are (haploid/diploid)

Answer 15

diploid

Question 16

Where are the mitotic cycle checkpoints

Answer 16

G1/S transition, G2/M transition and M checkpoint

Question 17

How does the regulation at G2 happen to make a mitotic clock?

Answer 17

MPF phosphorylates other proteins allowing mitosis to commence. However MPF can only form when enough cyclin has accumulated, which happens by the G2 phase which activates Cdk.

Question 18

What is M-phase promoting factor made of

Answer 18

cyclin + cyclin dependent kinase

Question 19

What does the G1 checkpoint check for and what happens if it doesn’t pass

Answer 19

undamaged DNA, cell size, nutrition and other signals (cyclins). If it doesn’t pass it may exit for G0 or stay rested at G1

Question 20

What does the M checkpoint check during mitosis

Answer 20

that all the chromosomes are appropriately attached to spindles

Question 21

Checkpoints rely on …

Answer 21

external signals such as growth factor via signal transduction pathways

Question 22

IF checkpoints didn’t work

Answer 22

could result in uncontrolled growth - tumours, -> cancer

Question 23

What causes cancer

Answer 23

acquired changes (effecting specific cells) and inherited DNA changes- increased susceptibility that alters protein function which can result in loss of cell cycle control.

Question 24

What mutations in what genes result in cancer

Answer 24

mutations in Proto-oncogenes that stimulate cell proliferation render them active in the absence of growth factors.
The mutation of tumour suppressor genes makes them lose their ability to inhibit cell division

Question 25

acquired change in DNA is from

Answer 25

viruses, UV damage, toxins, drugs

Question 26

What are some tumor suppressing genes

Answer 26

TP53

Question 27

3 different ways that proto-oncogene can be turned to an oncogene

Answer 27

mutation within gene results in hyperactive growth stimulating protein. Multiple copies of the gene at normal strength. Gene moved to new position produced under different control so excess produced.

Question 28

Two examples of proto-oncogenes

Answer 28

Ras and Myc

Question 29

how many somatic mutations are typically required for the generation of a cancer cell. Do these occur in both types

Answer 29

Multiple, yes

Question 30

Describe the first meiosis

Answer 30

prophase (crossing over between homologous chromosomes) metaphase (tetrads line up) anaphase (homologous chromosomes separate, sister chromatids remain attached). Telophase (each cell has one of the replicated chromosomes)

Question 31

meiosis II occurs in the daughter cells of meiosis I and forms

Answer 31

4 daughter cells with haploid number of chromosomes

Question 32

Whats the difference between the meiosis and mitosis

Answer 32

It doesn’t occur in mitosis, in meiosis it occurs during prophase 1 along with crossing between non sister chromatids.

Question 33

What are the sources of variations

Answer 33

independent assortment at metaphase, crossing over a prophase and fusion between two gametes.