Exam 2 (12-4-12)

Question 1

What is a chromosome?

Answer 1

A molecule of DNA with some associated proteins.

Question 2

What is chromatin?

Answer 2

Chromatin is what eukaryotic chromosomes are composed of; it is a complex of DNA and protein.

Question 3

What is a nucleosome?

Answer 3

A nucleosome is a complex of DNA wrapped around histone proteins that forms chromatin.

Question 4

What is heterochromatin?

Answer 4

Heterochromatin is the most highly packed DNA; genes in this form of DNA are inactive and are not available for expression.

Question 5

What is euchromatin?

Answer 5

Euchromatin is DNA that is normally less tightly packaged, only going to the most condensed form during cell division; this form of DNA allows its genes to be accessed and used.

Question 6

How many chromosomes do human cells have?

Answer 6

46 chromosomes (23 nearly identical pairs)

Question 7

What does diploid mean?

Answer 7

Diploid (2n) is when 2 of each chromosome type are present, like in humans.

Question 8

What does haploid mean?

Answer 8

Haploid (1n) is when only one set of each chromosome is present. The human haploid number is 23.

Question 9

Are human gametes (eggs and sperm) haploid or diploid?

Answer 9

Haploid

Question 10

What are homologous chromosomes?

Answer 10

Homologous chromosomes are the two chromosomes in one pair that are not identical because one is donated maternally and the other is donated paternally.

Question 11

What is an allele?

Answer 11

An allele is a different copy of the same gene.

Question 12

What is a centromere?

Answer 12

The centromere is the location where the two identical copies of DNA molecules (sister chromatids) are attached together.

Question 13

What are sister chromatids?

Answer 13

Sister chromatids are attached identical DNA strands that are held together by a centromere.

Question 14

What is a karyotype?

Answer 14

A karyotype is a picture of the condensed chromosomes of a cell that are ready to divide.

Question 15

What are the 3 major parts of the cell cycle?

Answer 15

The cell cycle is composed of 3 major parts: 1. Interphase 2. Mitosis 3. Cytokinesis

Question 16

What are the detailed portions of the cell cycle?

Answer 16

1. Interphase: G1, S, G2
2. Mitosis: Prophase, Metaphase, Anaphase, Telophase
3. Cytokinesis

Question 17

How long do cells typically spend in interphase?

Answer 17

90% of the cell’s lifespan.

Question 18

What is the G1 phase of interphase?

Answer 18

G1 is the growth phase of interphase, where cells increase in size, produce proteins and organelles, and generally engage in “growing up.” This is where cells spend most of their life.

Question 19

What is the S phase of interphase?

Answer 19

The S phase of interphase is the DNA synthesis phase, during which each chromosome is copied to produce attached sister chromatids.

Question 20

What is the G2 phase of interphase?

Answer 20

The G2 phase is the second growth phase, during which the cell produces copies of other cellular components in preparation for cellular division.

Question 21

What has occurred by the end of interphase of the cell cycle?

Answer 21

The cell has grown up, made an extra copy of its DNA, and produced much of the cellular machinery it needs to divide.

Question 22

What two subphases are part of the cell cycle’s “mitotic phase”?

Answer 22

The M phase (mitosis) and cytokinesis.

Question 23

What is the main goal/challenge of mitosis?

Answer 23

To use nuclear division to split the chromatids while making sure that each new cell will get ONE complete set of chromosomes, no more, no less.

Question 24

What are the 4 steps of mitosis?

Answer 24

Prophase, Metaphase, Anaphase, Telophase

Question 25

What occurs during cytokinesis?

Answer 25

Cytokinesis is the final, physical splitting of the overall cell itself to produce two distinct daughter cells, each with one full complement of chromosomes.

Question 26

What is the kinetochore?

Answer 26

The kinetochore is a disc structure formed by proteins where the spindle fibers will attach to pull apart the sister chromatids.

Question 27

What are spindle fibers?

Answer 27

Spindle fibers are microtubules that help pull sister chromatids to the opposite ends of the dividing cell.

Question 28

What occurs during prophase?

Answer 28

The nuclear membrane disintegrates and the nucleoli disappear; chromosomes condense; kinetochores and spindle fibers form.

Question 29

What occurs during metaphase?

Answer 29

The mitotic spindle fibers attach to the kinetochores on the sister chromatids and move the chromosomes toward the middle of the cell until they are lined up along the metaphase plate.

Question 30

What is a metaphase plate?

Answer 30

An imaginary plane at the cell's equator where the chromosomes line up before being pulled apart.

Question 31

What occurs during anaphase?

Answer 31

The spindle fibers begin to shorten, pulling the sister chromatids apart toward the opposite poles of the cell, making each chromatid now its own independent chromosome.

Question 32

What occurs during telophase?

Answer 32

The chromosomes reach opposite poles of the cell and a new nuclear membrane begins to form around them; chromosomes uncondense and the nucleolus reappears. The cell is now ready for cytokinesis!

Question 33

When does cytokinesis actually begin?

Answer 33

Typically, at some point during telophase.

Question 34

How does cytokinesis occur in animal cells?

Answer 34

A constricting set of actin filaments creates a cleavage furrow around the cell until it divides in two.

Question 35

How does cytokinesis occur in plant cells?

Answer 35

Because plant cells have a cell wall, a "cell plate" forms inside the cell that cuts across the spindle apparatus; the cell plate grows outward until it reaches the plasma membrane then fuses, separating the cytoplasms of the new daughter cells.

Question 36

What are the three cell cycle checkpoints?

Answer 36

1. G1/S Checkpoint 2. G2/M Checkpoint 3. Spindle Checkpoint

Question 37

What is the G1/S checkpoint?

Answer 37

Cell must decide whether to continue to S phase and prepare for division, to continue growth, or to rest.

Question 38

What is the G2/M checkpoint?

Answer 38

Cell needs to check that the DNA has replicated properly and the other components needed for cell division are ready.

Question 39

What is the Spindle checkpoint?

Answer 39

Occurs during metaphase and determines whether the cell will go continue through mitosis and back to G1.

Question 40

What happens if the cell does not pass the checkpoint?

Answer 40

The cell cycle is arrested and it will not continue on.

Question 41

What are kinases?

Answer 41

Kinases are enzyme which add phosphate to other molecules and are important in cell cycle control because the phosphorylation may have the effect of turning on or off a particular enzyme.

Question 42

What is Cyclin-dependent kinase (Cdk)?

Answer 42

It's an enzyme that we know to be important in cell cycle control because it interacts with different cyclin proteins for control of some of the cell cycle control points (G1/S0.

Question 43

What is M-phase-promoting factor (MPF)?

Answer 43

MPF is the Cdk that interacts with M-phase cyclin and is important at the G2/M checkpoint.

Question 44

What is the anaphase-promoting complex (APC)?

Answer 44

It's at the Spindle checkpoint and is activated if the chromsomes are correctly prepared for anaphase.