PAUSE - CELL CYCLE 1

Question 1

what are the stages of the cell cycle?

Answer 1

1. chromosome replication and cell growth
2. chromosome segregation
3. cell division

Question 2

what is part of the M phase?

Answer 2

nuclear division (mitosis) and cell division (cytokinesis)
only a small part of the cell cycle

Question 3

between what two phases of mitosis does an abrupt change in biochemical state of the cell happen?

Answer 3

between metaphase and anaphase

Question 4

when is the point of no return in cell division?

Answer 4

between metaphase and anaphase
after that point the cell has to divide

Question 5

when does DNA replication happen?

Answer 5

S phase of interphase

Question 6

what are the phases of the cell cycle?

Answer 6

G1
S phase
G2
M phase (mitosis and cytokinesis)

Question 7

what happens to the cell cycle at high temperatures?

Answer 7

the cell continues normally till it reaches a specific step that it is unable to complete
continues to grow but doesnt continue, becomes abnormally large
halts depending on what biochemical reserve they run out of

Question 8

how can the effect of a cdc mutation be seen under a microscope?

Answer 8

in a normal population buds vary in size according to cell cycle
in a mutated population they are all the same size because they all stop at the same stage

Question 9

how does oocyte growth and cell cleavage work in the frog?

Answer 9

oocyte grows without dividing for many months and matures into an egg
at fertilisation egg divides rapidly (1 division every 30 minutes)
multicellular tadpole formed within day or two
cells get smaller but embryo remains same size
growth starts when tadpole begins feeding

Question 10

how was the cell cycle studied in a cell free system?

Answer 10

large batch of activate frog eggs broken by gentle centrifugation
undiluted cytoplasm collected and sperm nuclei added to it, together with TP
sperm nuclei decondense and go through repeated cycles of DNA replication and mitosis
indicated that cel cycle control system is operating in the cell free cytoplasm extract

Question 11

how to differentiate cells that are in mitosis vs not in an electron micrograph?

Answer 11

cells not in mitosis are flat and attached to others
cells that are round are in mitosis

Question 12

how does a flow cytometer (or also called fluorescence activated cell sorter FACS) analyse DNA content?

Answer 12

cells are stained with dye that becomes fluorescent when it binds to DNA
amount of fluorescence is proportional to teh amount of DNA in each cell

Question 13

in which categories do cells fall in a flow cytometer graph?

Answer 13

those in the G1 phase: unreplicated complement of DNA (most abundant)
those in the G2 or M phase: have a fully replicated complement of DNA (twice the G1 content)
in the S phase: intermediate amount of DNA content
less than 1: cells when they die
more than 2: too much replication, cancer

Question 14

what are the advantages of studying the cell cycle in yeast?

Answer 14

• Small genome
• Fast duplication (about 20 minutes)
• Haploid genome: easy to modify or delete genes