Lecture 6: Cell Replication

Question 1

bacterial cell division

• aka
• occurs in
• how

Answer 1

• aka fission
• prokaryotes
• chromosomes replicate and are pushed apart by a ring of contractive proteins that squeeze and fold cell wall

Question 2

• meiosis

- mitosis

Answer 2

• meiosis: produces reproductive cells called gametes

- mitosis: produces all other cell types (somatic cells)

Question 3

chromosomes

- made how

Answer 3

• double helix binds to histones which package and order DNA into structural units called nucleosomes
• eventually become highly condensed during cell division into x shaped chromosomes

Question 4

can you label the parts on a chromosome? (2)

Answer 4

• sister chromatids

- centromere

Question 5

microtubules

• structure
• function
• metaphase:
• anaphase:

Answer 5

• polymers of tubulin
• alpha and beta tubulin dimers
• attach to centrosome and chromosome at kinetochore (see notes)
• in the metaphase they grow and move centrosomes apart
• shorten at the positive end during anaphase

Question 6

centrosome

Answer 6

• made up of microtubules and centrioles

- microtubule organizing centre

Question 7

interphase

Answer 7

occurs before mitosis; cell growth; DNA duplicates and the nucleus and organelles are duplicated and separated

Question 8

list all the stages of mitosis in order (6)

Answer 8

• prophase
• prometaphase
• metaphase
• anaphase
• telophase
• cytokinesis

Question 9

briefly describe: prophase

Answer 9

chromosomes condense; spindles form

Question 10

briefly describe: prometaphase

Answer 10

• nuclear envelope breaks down

- microtubules contact chromosome in the centre

Question 11

briefly describe: metaphase

Answer 11

• chromosomes move to the middle of the cell

Question 12

briefly describe: anaphase

Answer 12

• sister chromatids separate; daughter chromosomes are pulled apart

Question 13

briefly describe: telophase

Answer 13

• nuclear envelope forms and chromosomes decondense

Question 14

briefly describe: cytokinesis

Answer 14

• cell division begins

- actin/ myosin ring contracts

Question 15

in plant cells, how does cytokinesis differ?

Answer 15

• microtubules move vesicles in place to form a new membrane

Question 16

List the key proteins in mitosis and their jobs (5)

Answer 16

• cohesins: hold sister chromatids together
• condensins: compact DNA
• nuclear lamins: stabilize nucleus
• microtubules (tubulin): move chromosomes to opposite poles
• kinetochore proteins: attach microtubules to DNA

Question 17

control of cell cycle

• what are the 4 stages?
• where are the 3 checkpoints? what do each of them check for (1st stage: 4 things, 2nd stage: 2 things, 4th stage: 2 things)

Answer 17

• interphase stages: G1, S, G2, M
• end of G1: checks for appropriate cell size, nutrient sufficient, DNA undamaged, and social signals (prevents liver growing in the brain)
• end of G2: replication finished; DNA undamaged
• M checkpoint: are chromosomes attached to spindle? Have chromosomes segregated?
• note: mature cells do not go through checkpoint 1 and just go to G(o)

Question 18

apoptosis

Answer 18

cell death

Question 19

Why do cancer cells divide uncontrollably?

Answer 19

They ignore social signals

Question 20

Everytime a cell divides, what increases?

Answer 20

the chance of mutation