Week Ten: Cell Division and Cancer

Question 1

Why is cell division neccesary?

Answer 1

Growth/development, reproduction, maintenance of the body, and wound healing.

Question 2

The Cell Cycle

Answer 2

• the cell cycle is an orderly set of events in eukaryotes that involves cell growth and nuclear divisions
• the cell cycle can be divided into two major events: interphase (normal cell function) and mitosis (cell division)

Question 3

Cell Cycle Checkpoints

Answer 3

1. occurs near the end of G1
2. occurs at the G2/M transition
3. SAC occurs during metaphase
   *G1 chooses whether or not the cell will divide (unexpected problems: DNA damage or replication errors) and internal/external conditions are checked
   *G2 checks DNA integrity and DNA replication (if the damage is irreparable, the cell may undergo apoptosis or cell death)
   *Spindle checks for chromosome attachment to the spindle

Question 4

Give definitions and examples of asexual and sexual reproduction

Answer 4

In asexual reproduction, one parent copies itself to form a genetically identical offspring. Examples: binary fission and vegetative propagation. In sexual reproduction, an organism combines the genetic information from each parent and is genetically unique. Examples: humans and fish.

Question 5

What does it mean to be haploid? What does it mean to be diploid?

Answer 5

Haploids contain 1 copy of every chromosome while diploids contain 2 copies of every chromosome (homologous chromosomes)

Question 6

How do chromatids differ homologous chromosome pairs?

Answer 6

Sister chromatids are genetically identical while homologous chromosomes are composed of two different chromosomes that are not genetically identical despite containing the same sets of genes.

Question 7

How do bacteria divide?

Answer 7

Bacteria divide using binary fission: the process of a cell growing to twice its starting size and then splitting into two.

Question 8

What are the two phases of the cell cycle? When is DNA duplicated?

Answer 8

The two phases of the cell cycle are mitosis and interphase. DNA is duplicated during mitosis as it ends in cell division.

Question 9

What are some of the pros and cons to the accumulation of mutations in the cell’s DNA?

Answer 9

Mutations are only beneficial if they are done through natural selection or evolution. They can form new proteins that help organisms adapt to new environments. Some cons are genetic disorders or cancer.

Question 10

All cancers are characterized by

Answer 10

abnormally high rates of cell division.

Question 11

Why is cancer most prevalent in older people?

Answer 11

Over time, cells can become damaged and may lead to cancer forming later on in life.

Question 12

What is the most preventable cause of cancer in the U.S.?

Answer 12

Exposure to cigarette smoke/smoking.

Question 13

Why is cancer considered a “chain reaction”?

Answer 13

Because cancer can be inherited over generations between families.

Question 14

Mitosis

Answer 14

• The goal of the mitotic stage is to reproduce exact copies of the parent cells (for either developmental growth, repair, or replacement)
• All genetic info must be transmitted to the daughter cells

Question 15

1.S Phase

Answer 15

*DNA replication results in the formation of identical pairs of DNA molecules
*the centrosome is duplicated
*DNA repair activity occurs in cells

Question 16

2.Early Prophase

Answer 16

• chromatin condenses into chromosomes
• the centrosomes move to the opposite ends of the nuclear envelope
• nuclear envelope begins to dissolve

Question 17

3.Prophase

Answer 17

• spindle apparatus (a network of microtubules created from the centrosomes) begins to form
• cohesins disappear except at the centromere; chromatids become visible
• kinetochores, for movement, develop in the centromere regions

Question 18

4.Late Prophase/Prometaphase

Answer 18

*the mitotic spindle begins to capture and organize chromosomes
*chromosomes become condensed and compact
*the nuclear envelope breaks down, releasing the chromosomes

Question 19

5.Metaphase

Answer 19

• chromosomes align single file at the center of the cell (metaphase plate)

Question 20

6.Anaphase

Answer 20

• a protein at the kinetochores–cytoplasmic dynein–hydrolyzes ATP for energy to move chromosomes along the microtubules towards the poles
• the cell elongates

Question 21

7.Telophase

Answer 21

*daughter cells begin to form
*nuclear envelope begins to re-form
*nucleolus reappears
*cleavage furrow begins to form between newly forming cells
*chromosomes unwind