Cell Cycle

Question 1

what is a genome?

Answer 1

all the genetic info contained in the chromosomes of an organism

Question 1

what are chromosomes and chromatin?

Answer 1

chromosomes - packaged DNA

chromatin - “unwound” DNA that condenses itself during cell division

Question 2

what are diploid and haploid cells?

Answer 2

diploid - a complete set of 2 sets of chromosomes (2n = 46)

haploid - a half set of chromosomes (1n = 23), the gametes (sex cells) of both sexes (23 + 23 = 46)

Question 3

what are sister chromatids and a centromere?

Answer 3

sister chromatids - identical copies of one chromosome, held together at the centromere

Question 4

what are the three types of cell division?

Answer 4

mitosis - dividing of nucleus’ genetic code
cytokinesis - division of the cell’s cytoplasm
meiosis - diving of gamete cells

Question 5

what are the 3 big “stages” of cell division?

Answer 5

1. interphase
2. mitosis (also called M phase)
3. cytokinesis

Question 6

what are the 3 steps of interphase?

Answer 6

G1 - cells get bigger and make more proteins + organelles needed to make 2 cells

S - cell makes a duplicate copy of its DNA in the nucleus

G2 - cell makes more proteins/organelles, and begins to move its contents around in preparation to split

Question 7

what are the five stages of mitosis?

Answer 7

1. prophase
2. pro-metaphase
3. metaphase
4. anaphase
5. telophase

Question 8

what occurs in a cell during prophase?

Answer 8

-mitotic spindles begin to form
-chromatin begins to condense into chromosomes
-nucleolus (where ribosomes are made) disappears

Question 9

what occurs in a cell during prometaphase?

Answer 9

-chromosomes become very compact and held together by centromeres
-nuclear envelope breaks down, releasing chromosomes into cell cytoplasm
-mitotic spindle grows more, some microtubules begin to “grab” some centromeres

Question 10

what occurs in a cell during metaphase?

Answer 10

-chromosomes align at the “metaphase plate,” a plane where they all line up
-kinetochores of each chromosome should be attached to opposite spindles

Question 11

what occurs in a cell during anaphase?

Answer 11

-microtubules attached to centromeres begin to pull apart the sister chromatids, forming 2 pairs of each chromosome
-microtubules not attached to centromeres will push the chromosomes away to their respective corners of the cell

Question 12

what occurs in a cell during telophase and cytokinesis?

Answer 12

-mitotic spindle is broken down
-nucleolus and nuclear envelope begin to reform
-a “cleavage furrow” begins to form which “pinches” the cell in half, forming 2 new cells from one cell

Question 13

what is the mitotic spindle?

Answer 13

-a bunch of microtubules that control chromosome movement, form during prophase and prometaphase
-arise from centrosomes in animal cells
-

Question 14

what are kinetochores?

Answer 14

a patch of motor proteins found at the centromere of each sister chromatid, each sister chromatid has one. these proteins bind to the mitotic spindles that pull them

Question 15

what are kinetochore and non kinetochore microtubules?

Answer 15

-kinetochore microtubules are microtubules from the spindles that attach to the kinetochore of chromosomes and move them to the metaphase plate

-non kinetochore microtubules are microtubules that overlap and elongate the cell during anaphase

Question 16

how is plant cell cytokinesis different from animal cell cytokinesis?

Answer 16

animal cells - cell gets pinched @ cleavage furrow, gets split in half

plant cells - golgi vesicles form in middle of cell and fuse together to form a new cell wall that separates two cells.

Question 17

how does cell type dictate frequency of cell division?

Answer 17

-skin cells will continually divide as the body is always being microscopically “damaged” and sloughing off dead cells

-some cells can divide but only if they need to [eg , liver cells]

-some cells cannot divide, such as mature nerve and muscle cells

Question 18

what is the “cell cycle”?

Answer 18

-a series of events that are maintained and directed by a cell cycle control system, a set of molecules that triggers and coordinates certain key events in the cycle, regulated @ checkpoints`

Question 19

what are cell cycle checkpoints?

Answer 19

-points in the cell cycle where division is stopped until a go signal is received, can be an internal or external signal

Question 20

where do the cell cycle checkpoints occur?

Answer 20

-end of G1 = go or no go signal
-end of G2
-during metaphase

Question 21

what are cyclins and cyclin dependent kinases?

Answer 21

proteins that regulate cell cycle checkpoints
-Cdks are always present, but only activate when bound to with cyclin
-serve as go ahead signals for G1 and G2 checkpoints

Question 22

what is MPF / maturation promoting factor?

Answer 22

-a cyclin-cdk complex that triggers a cell to pass from G2 into the M phase of cell division
-this factor is self regulating and degrades its cyclins in anaphase

Question 23

what is the M phase checkpoint?

Answer 23

-occurs during metaphase
-controls start of anaphase, only goes ahead when all kinetochores are attached to kinetochore microtubules to ensure all cells have equal #s of chromosomes

Question 24

what are external growth factors?

Answer 24

-proteins released by one cell that stimulate another to divide
-ex. platelet derived growth factor - stimulates cell division at a wound to clot / help heal

Question 25

what is density dependent inhibtion?

Answer 25

-when cells touch each other, inhibiting signals are sent to both to stop excess cell growth

Question 26

what is anchorage dependence?

Answer 26

-cells must be attached to a substratum layer in order to divide, stops excess / cancerous cell growth