Cell Cycle

Question 1

Why do cells divide?

Answer 1

Problems happen when they get too big (DNA overload and inefficient transport)

Question 2

What are the stages of interphase?

Answer 2

G1-cell grows, builds organelles, proteins, enzymes, etc.
S-DNA is synthesized and replicated, preparing for division
G2-cell finishes growth and preparation to dovide

Question 3

What are the phases of mitosis? (In order)

Answer 3

Prophase, metaphase, anaphase, telophase

Question 4

What happens during prophase?

Answer 4

Chromatin condenses into chromosomes, nuclear envelope breaks down, spindle fibres develop, centrioles start moving to the poles

Question 5

What happens during metaphase?

Answer 5

Chromosomes line up single file in centre of cell, spindle fibres attach to chromosomes

Question 6

What happens during anaphase?

Answer 6

Sister chromatids are pulled to opposite ends of the cell

Question 7

What happens during telophase?

Answer 7

Chromosomes have arrived at poles, nuclear envelopes reform, chromosomes start to unwind

Question 8

What is cytokinesis?

Answer 8

Separation of the cytoplasm, cleavage furrows form during telophase, though it’s not part of mitosis. Plant cell cytokinesis involves formation of a cell plate between new cells.

Question 9

What is the result of mitosis?

Answer 9

Two, genetically identical, diploid cells

Question 10

What is the purpose of meiosis?

Answer 10

To form gametes, or sex cells

Question 11

What are homologous chromosomes?

Answer 11

Chromosomes pairs similar in length, gene position, and centromere position

Question 12

What happens during prophase I?

Answer 12

Chromatin condenses, nuclear membrane breaks down, formation of tetrads, cross-over, spindle fibre development

Question 13

What happens during metaphase I?

Answer 13

Tetrads line up 2 by 2 in the centre of the cell, spindle fibres attach

Question 14

What happens during anaphase I?

Answer 14

Tetrads are pulled apart

Question 15

What happens during telophase I?

Answer 15

Chromosomes arrive at their destinations, with n at each pole

Question 16

What happens during Meiosis II?

Answer 16

The events are essentially the same as mitosis, just with half the normal number of chromosomes.

Question 17

What is a karyotype?

Answer 17

An image of a person’s chromosomes organized into homologous pairs

Question 18

What are autosomes?

Answer 18

Chromosome pairs 1-23, they code for most of our bodies

Question 19

What are sex chromosomes?

Answer 19

Pair 23, determine an organism’s sex. X has functions outside of sex determination, Y does not

Question 20

What is nondisjunction?

Answer 20

When homologous chromosomes fail to separate during anaphase I, results in two gametes having an extra chromosome, and two missing one

Question 21

What causes Down Syndrome?

Answer 21

Trisomy 21, or three chromosomes in the 21st pair, instead of the normal two

Question 22

What are some examples of sex chromosome disorders?

Answer 22

Turner’s syndrome in females, only one X can’t do meiosis. Klinefelter’s in males, XXY, extra x interferes with meiosis, usually sterile

Question 23

What are the four checkpoints of the cell cycle?

Answer 23

G1/S, S, G2/M, Metaphase/anaphase

Question 24

What are the stimulating proteins of the G1/S checkpoint?

Answer 24

Growth factors stimulate G1 cyclin release, which mind with CDKs to move the cell to S

Question 25

What are the inhibiting proteins of the G1/S checkpoint?

Answer 25

p53 checks for DNA damage, and can stall the cell for repairs or initiate apoptosis if the damage is too much. Rb prevents entering S phase without signals from growth factors

Question 26

What are the stimulating proteins of the S phase checkpoint?

Answer 26

S-phase cyclins activate CDKs which stimulate the replication of DNA

Question 27

What are the inhibiting proteins of the S checkpoint?

Answer 27

Ataxia telangiectasia mutated (ATM) checks for breaks in the replicated DNA strands, and can activate BRCA1 to repair those strands, or initiate apoptosis

Question 28

What are the stimulating proteins of the G2/M checkpoint?

Answer 28

M-phase cyclins bind to their CDKs and send the cell into mitosis

Question 29

What are the inhibiting proteins of the G2/M checkpoint?

Answer 29

p53 comes back!

Question 30

What are the stimulating proteins of the M-check checkpoint?

Answer 30

Anaphase-promoting complex/cyclosome (APC/C) activates once all chromosomes are attached to the spindle fibres, and stimulates destruction of the proteins holding sister chromatids together to allow anaphase to occur

Question 31

What are the inhibiting proteins of the M-check checkpoint?

Answer 31

Mitotic arrest deficient (MAD) proteins inhibit APC/C from activating if chromosomes are not properly attached to the spindle, stopping anaphase from occuring

Question 32

How do CDKs work?

Answer 32

Cyclin-dependant kinases are proteins that must bind to cyclins do function. Once activated, they stimulate various stages of the cell cycle by activating other proteins.

Question 33

How do cyclin levels contribute to cell cycle regulation?

Answer 33

Cyclin levels rise and fall cyclically, controlling the number of CDKs that can be active at a time. CDK thresholds must be met for them to influence the progression through stages of the cell cycle