1.6 (Topic 1)

Question 1

State the function of mitosis.

Answer 1

The function of mitosis is to create two daughter cells with genetically identical nuclei as the parent cell

Question 2

List four processes which involve mitosis

Answer 2

Tissue repair/ replacement
Organismal growth
Asexual production
Development (of embryos)

Question 3

State the names of the four phases of mitosis

Answer 3

Prophase
Metaphase
Anaphase
Telophase

Question 4

Draw typical eukaryotic cells as they would appear during the interphase

Answer 4

Nucleus intact
Nucleolus visible
DNA as chromatin
DNA is unreplicated

Question 5

Draw typical eukaryotic cells as they would appear during the prophase

Answer 5

Nuclear membrane breaking down 
Nucleolus fading 
DNA supercoiling into the chromosome 
Spindle fibers form 
Centrioles move towards cell poles

Question 6

Draw typical eukaryotic cells as they would appear during the metaphase

Answer 6

Replicated chromosomes align at the cell equator

Question 7

Draw typical eukaryotic cells as they would appear during the anaphase

Answer 7

Identical chromatids (now individual unreplicated chromosomes) are pulled towards the poles of the cell

Question 8

Draw typical eukaryotic cells as they would appear during the telophase

Answer 8

Nuclear membrane reforming
Nucleolus reforming
DNA recoiling to become chromatin
Spindle fibers degrade

Question 9

Outline the process of metaphase, inclusive of the role of microtubules and the kinetochore.

Answer 9

• Replicated chromosomes align at the cell equator
• a protein complex called the kinetochore located at the centromere is connected to microtubules (a type of spindle fiber)

Question 10

Outline the process of anaphase.

Answer 10

Identical chromatids (now individual unreplicated chromosomes) are pulled towards the poles of the cell

Question 11

Outline four events that occur during telophase.

Answer 11

Nuclear membrane reforming
Nucleolus reforming
DNA uncoiling to become chromatin
Spindle fibers degrade

Question 12

Describe the structure of a replicated chromosome, including the centromere and sister chromatids.

Answer 12

• Chromosomes are supercoiled strands of DNA
• Replicated chromosomes mean that there are identical copies of DNA called sister chromatids (formed during DNA replication in S phase) attached to each other at the centromere

Question 13

Explain why chromosomes must condense during mitosis.

Answer 13

To condense means to make DNA denser, or more tightly packed. DNA condenses during mitosis so that it can more easily be moved to the poles of the cell without getting tangled and/or broken

Question 14

Define cytokinesis.

Answer 14

Cytokinesis is the division of the cytoplasm of a parent cell into two daughter cells

Question 15

State the difference between mitosis and cytokinesis.

Answer 15

Mitosis refers to the division of the nucleus (nuclear DNA) whereas cytokinesis is the division of the cytoplasm (and organelles in it).

Question 16

Contrast cytokinesis in plant and animal cells.

Answer 16

Cytokinesis is different in plant and animals cells because plant cells must create new cell wall between the daughter cells; animal cells do not have to form a cell wall

Question 17

List examples of metabolic reactions occurring during cell interphase.

Answer 17

The majority of the cell cycle is spent in interphase. During interphase “G1”, the cell is performing its specialized function, which requires extensive protein synthesis. During interphase “S”, DNA replication occurs.

Question 18

Outline events of G1, S, G2, and G0 phases of interphase.​

Answer 18

G1: cell grows and performs its specialized functions
S: the DNA replicates
G2: the cell makes the proteins required for mitosis and cytokinesis
G0: the cell is neither dividing nor preparing to divide

Question 19

Explain the role of cyclin and cyclin-CDK complexes in controlling the cell cycle.

Answer 19

The cell cycle must be controlled so that cells are only dividing when necessary, not continuously. The cell also needs to time for progession through the cell cycle so that it moves from one phase to the next only when all the steps are complete.

Cyclins are protein molecules whose concentration cycle up and down as the cell progresses through the cell cycle. Cyclins attach to other molecules, cyclin-dependent kinases (CDK) to activate progression through the cell cycle. If there is a low concentration of cyclin, the CDK will not be active and the cell cycle will freeze.

Question 20

State the role of cyclins D, E, A and B in the cell cycle.

Answer 20

Cyclin D: causes progression of the cell through G1 and into S phase
Cyclin E: causes the cell to prepare for DNA replication
Cyclin A: initiates DNA replication in S phase and prepares the cell for mitosis during G2
Cyclin B: progresses the cell through prophase and metaphase. Must degrade for the cell to begin anaphase

Question 21

define tumor

Answer 21

a mass of tissue caused by abnormal cell division

Question 22

define benign

Answer 22

a tumor that lacks the ability to invade other tissues or metastasize

Question 23

define malignant

Answer 23

a tumor made of cells that can invade other tissues and metastasize

Question 24

define cancer

Answer 24

a disease caused by a malignant tumor

Question 25

define mutagen

Answer 25

an agent that changes the genetic material of an organism (physical, chemical, or biological)

Question 26

define carcinogen

Answer 26

mutagens that lead to the formation of cancer

Question 27

define oncogenes

Answer 27

a gene that has the potential to cause cancer

Question 28

Describe why mutagens are not necessarily carcinogens.

Answer 28

A mutagen induces mutations in DNA. If the mutation results in uncontrolled cell division and cancer, then the mutagen is also a carcinogen

Question 29

Describe how cancer arises, referring to the accumulation of mutations over time.

Answer 29

Cells become cancerous after mutations accumulate in genes that control the cell cycle.

Question 30

Explain the relationship between oncogenes, tumor suppressor genes, and cancer

Answer 30

Proto-oncogenes are normal genes that code for proteins (cyclins) that cell move through the cell cycle

When proto-oncogenes mutate, they become oncogenes. Oncogenes move the cell through the cell cycle even when it shouldn’t divide

Tumor-suppressor genes are normal genes that code for proteins that stop a cell from dividing when it shouldn’t. When tumor- suppressor gene mutates, the cell will divide even when it shouldn’t

Question 31

Explain the use of correlations to determine the relationship between two variables (inclusive of positive and negative correlations).

Answer 31

Correlations are used to show how related two variables are to each other. Correlations do not necessarily show causation between variables.
Positive correlation (direct) - as X increases, Y increases
Negative correlation (indirect) - as X increases, Y decreases

Question 32

Explain why the existence of a correlation does not necessitate a causal relationship between two variables.

Answer 32

For any two correlated variables, the following relationships are possible:
X causes Y
Y causes X
X and Y are consequences of a common cause, but do not cause each other
X causes Z which causes Y
The correlation between X and Y is a coincidence

Question 33

Outline the relationships between smoking and cancer.

Answer 33

Epidemiologists noticed a relationship between smoking and rates of lung cancer. Since cancer rates when up as smoking rates went up, epidemiologists concluded that there is a positive (direct) relationship between smoking and lung cancer.

Substantial evidence has now been collected to determine that this is a CAUSAL relationship - smoking can cause the development of cancer.

Question 34

State the formula for the calculation of a mitotic index.

Answer 34

Mitotic Index = # of cells in mitosis/ total number of cells

Question 35

Calculate the mitotic index of tissue as seen in a micrograph.

Answer 35

Mitotic Index = # of cells in mitosis (shown in red) / total number of cells

Question 36

Outline the use of mitotic index calculations in the diagnosis and treatment of cancer.

Answer 36

Diagnosis: the higher the mitotic index relative to a tissue specific standard, the more likely a tissue is cancerous.

Treatment: cancer treatments work by stopping cell division, so if a cancer treatment is working fewer cells will be in mitosis. As a result, the mitotic index will decrease if a treatment is working.

Question 37

Describe the formation of the cleavage furrow in animal cell cytokinesis.

Answer 37

During cytokinesis in animal cells, a ring of actin filaments forms at the metaphase plate. The ring contracts, forming a cleavage furrow, which divides the cell in two.

Question 38

Describe the formation of the middle lamella and cell wall in plant cell cytokinesis.

Answer 38

The middle lamella is a layer of pectin (a polysaccharide carbohydrate) which cements the cell walls of two adjoining plant cells together. The Golgi buds vesicles containing pectin. These vesicles move to and align at the cell equator. The vesicles fuse, forming a continuous phospholipid membrane with pectin. “Cell Plate” Additional vesicles bring and secrete cellulose to the cell plate forming the cell wall.