The Cell Cycle

Question 1

What occurs during mitosis (M phase)?

Answer 1

Mitosis is the phase where a cell divides into two daughter cells

Question 2

What does it mean for cells to proliferate and differentiate?

Answer 2

Proliferation: divide
Differentiate: specialize

Question 3

What are stem cells?

Answer 3

Cells that have the ability to proliferate

Question 4

What occurs during G0, G1, G2, and S phase? (interphase)

Answer 4

G0: cells are not actively ready to divide
G1: growth
G2: growth and final preparation for division
S: phase during which DNA is replicated and growth

interphase: chromosomes duplicate and the copies remain attached to eachother

Question 5

What is a centromere?

Answer 5

Specialized DNA sequence that links a pair of sister chromatids

Question 6

What is a kinetochore?

Answer 6

A complex of proteins associated with the centromere to which the microtubules of the spindle attach

Question 7

What occurs during prophase? (mitosis)

Answer 7

In the nucleus, chromosomes condense and become visible

-spindle fibers emerge from the centrosomes and form in the cytoplasm
-nuclear envelope breaks down
-centrosomes move towards opposite poles

Question 8

What occurs during metaphase? (mitosis)

Answer 8

The copied chromosomes align in the middle of the metaphase plate

-each sister chromatid is attached to a spindle fiber originating from opposite poles

Question 9

What occurs during anaphase? (mitosis)

Answer 9

Chromosomes separate into two genetically identical groups and move to opposite ends of the spindle

-centromeres split in two
-sister chromatids (now called chromosomes), are pulled to opposite poles
-certain spindle fibers begin to elongate the cell

Question 10

What occurs during telophase? (mitosis)

Answer 10

Nuclear membranes form around each of the two sets of chromosomes, the chromosomes begin to spread out, and the spindle begins to break down

-chromosomes arrive at opposite poles and begin to decondense
-nuclear envelope material surrounds each set of chromosomes
-the mitotic spindle breaks down
-spindle fibers continue to push poles apart

Question 11

What occurs during cytokinesis?

Answer 11

The cell splits into two daughter cells, each with the same number of chromosomes as the parent. In humans, these cells have two copies of 23 chromosomes and are called diploid

a cleavage furrow separates the daughter cells

Question 12

How many chromosome pairs do human cells contain?

Answer 12

23 pairs (46 chromosomes)

Question 13

What occurs in meiosis?

Answer 13

Meiosis is the cell division of sperm and egg cells and guarantee genetic diverstiy

Question 14

What occurs in prophase 1 (meiosis)

Answer 14

The chromosomes condense, and the nuclear envelope breaks down. Crossing over occurs and the chromosomes pair with their homologous partner forming a tetrad through synapsis (2 sets of chromosome pairs)

Question 15

What happens when chromosomes cross over?

Answer 15

crossing over between non sister chromatids exchanges genetic information

Question 16

What occurs before meiosis?

Answer 16

DNA replication

Question 17

What occurs during metaphase 1 (meiosis)?

Answer 17

Chromosomes line up along the metaphase plate with their homologous pair

Question 18

What occurs during anaphase 1 (meiosis)?

Answer 18

Homologous chromosomes are pulled towards the centrioles on each side of the cell.

The homologous pairs are only separated after this process, sister chromatids remain together

Question 19

What occurs during telophase 1 (meiosis)?

Answer 19

Chromosomes are completely pulled apart now and a new nuclear membrane forms

the cells are split via cytokinesis and each contain one of the replicated chromosomes from each homologous pair of chromosomes (haploid)

Question 20

What are the results of meiosis 1?

Answer 20

Two new cells are created each haploid in their DNA, but with 2 copies, are the result of meiosis I. Again, although there are 2 alleles for each gene, they are on sister chromatid copies of each other. These are therefore considered haploid cells. These cells take a short rest before entering the second division of meiosis, meiosis II.

Question 21

What occurs during prophase 2 (meiosis)?

Answer 21

The nuclear envelopes disappear and centrioles are formed. Microtubules extend across the cell to connect to the kinetochores of individual chromatids, connected by centromeres. The chromosomes begin to get pulled toward the metaphase plate.

Question 22

What occurs during metaphase 2 (meiosis)?

Answer 22

Similar to mitosis, the chromosomes line up with their centromeres on the metaphase plate. One sister chromatid is on each side of the metaphase plate.

Question 23

What occurs during anaphase 2 (meiosis)?

Answer 23

The sister chromatids separate. They are now called sister chromosomes and are pulled toward the centrioles on each end of the cell.

Question 24

What occurs during telophase 2 (meiosis)?

Answer 24

The cell is now divided into two and the chromosomes are on opposite ends of the cell. Cytokinesis occurs, and new nuclear envelopes are formed around the chromosomes. These resulting cells are gametes with haploid number of chromosomes

Question 25

What is the final result of meiosis?

Answer 25

4 haploid gametes

Question 26

From 2 parents, how many possible genetic variations are there for a fertilized egg?

Answer 26

70

Question 27

What causes cancer?

Answer 27

Anything that causes mutation (permanent changes in DNA) that results in abnormal cell growth (uncontrolled mitosis) and due to faulty immune system