Chapter 8

Question 1

Why can a eukaryotic cells not simply split into two?

Answer 1

Because then only one daughter cell would inherit the nucleus and the DNA. A cell’s cytoplasm only splits after its DNA has been copied and packaged into more than one nucleus.

Question 2

What is Mitosis?

Answer 2

Mitosis is a nuclear division mechanism that occurs in somatic (body) cells of multicelled organisms.

Question 3

What is Meiosis?

Answer 3

The basis of sexual reproduction, in humans and mammals gametes (sperm and eggs) develop from immature reproductive cells.

Question 4

Functions of Mitosis cytoplasm division (4).

Answer 4

In all multicelled eukaryotes, the basis of three processes:

1. Increases in body size during growth
2. Replacement of dead or worn-out cells
3. Repair of damaged tissues

In single-celled and many multicelled species, also the
basis of asexual reproduction

Question 5

Function of Meiosis cytoplasm division.

Answer 5

In single-celled and multicelled eukaryotes, the basis of sexual reproduction; precedes gamete formation or spore formation.

Question 6

Function of Prokaryotic fission.

Answer 6

In bacteria and archaeans alone, the basis of sexual reproduction.

Question 7

What are Sister Chromatids?

Answer 7

Two attached molecules of DNA (attached as one chromosome)

Question 8

What are Histones?

Answer 8

“Spools” of proteins. Under a microscope appears as beads on a string.

Question 9

What are Nucleosomes?

Answer 9

A “bead” of a histone, the smallest unit of structural organization in eukaryotic chromosomes.

Question 10

What is a Centromere?

Answer 10

The constricted region of a sister chromatid.

Question 11

What are Kinetochores?

Answer 11

Binding sites for microtubules that tether the chromatids.

Question 12

What is a Cell Cycle?

Answer 12

A series of events from one cell division to the next. Consists of: mitosis, cytoplasmic division, and interphase.

Question 13

What is Interphase?

Answer 13

Interphase consists of three stages that increases the mass, doubles the cytoplasmic components, and duplicates the DNA of a cell.

Question 14

What are the three stages of Interphase?

Answer 14

1. G1 - Interval (Gap) of cell growth and activity before the onset of DNA replication.
2. Time of “Synthesis” (DNA replication).
3. G2 - Second interval (Gap) after DNA replication where the cell prepares for division.

Question 15

What is the Chromosome Number?

Answer 15

The sum of all chromosomes in a cell of a given type.

Question 16

What are the four stages of Mitosis?

Answer 16

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

Question 17

What is the Bipolar Spindle?

Answer 17

A dynamic network of microtubules the grows from opposite poles of the cell during prophase.

Question 18

What does “Mitos” mean?

Answer 18

Comes from the Greek word “thread”.

Question 19

What happens to two sister chromatids during prophase?

Answer 19

The duplicated chromosomes condense and become threadlike, and then rod-shaped. New microtubules assemble.

Question 20

What is a Centrosome?

Answer 20

A region near the nucleus that will organize microtubules while they are forming.

Question 21

When is the Centrosome duplicated?

Answer 21

Just before prophase.

Question 22

What happens in the early stages of prophase?

Answer 22

Mitosis begins. DNA and its associated proteins have started to condense. Two chromosomes were inherited from the female parent. The
other two are their counterparts,
inherited from the male parent.

Question 23

What happens in the late stages of prophase?

Answer 23

The duplicated chromosomes
continue to condense. New
microtubules move one of two
pairs of centrioles to the opposite side of the nucleus. The nuclear envelope starts to break up.

Question 24

What happens during the transition from prophase to metaphase?

Answer 24

Microtubules penetrate the nuclear region and collectively form a bipolar spindle. Some tether one sister chromatid of each chromosome to a spindle pole. Others overlap at the spindle equator.

Question 25

What happens during metaphase?

Answer 25

All of the chromosomes have become lined up midway between the spindle poles. At this stage of mitosis, the chromosomes are in their most tightly condensed form.

Question 26

What happens during anaphase?

Answer 26

Sister chromatids separate as motor proteins moving along spindle microtubules drag them to opposite spindle poles. Other microtubules push the poles farther apart.

Question 27

What happens during telophase?

Answer 27

There are two clusters of chromosomes, which now decondense. Patches of new membrane fuse to form a new nuclear envelope. Mitosis is over.

Question 28

What results at the end of mitosis?

Answer 28

After cytoplasmic division, there are two daughter cells. Each is diploid: Its nucleus has two of each type of chromosome, just like the parent cell.

Question 29

What are Kinases?

Answer 29

A class of enzymes that can activate other molecules by transferring a phosphate group to them. When DNA is broken or incomplete, kinases can activate certain proteins that eventually lead to cell death or stopping the cell cycle.

Question 30

What are Growth Factors (checkpoints)?

Answer 30

Checkpoint proteins that activate genes that stimulate cells to grow and divide.

Question 31

How is a tumour formed?

Answer 31

When a cell’s continually dividing descendants are not stopped by a checkpoint protein and abnormal mass is formed.

Question 32

What are Neoplasms?

Answer 32

Moles and other tumours, or abnormal masses of cells that lost control over how they grow and divide.

Question 33

What are Cancers?

Answer 33

Abnormally growing and dividing cells of a malignant neoplasm, they physically and metabolically disrupt surrounding tissues.