U1L5

Question 1

What are somatic cells

Answer 1

Non reproductive cells

Question 2

How many sets of chromosomes do humans have? How many in total?

Answer 2

2
2 x 23 = 46

Question 3

What are gametes?

Answer 3

Reproductive cells

Question 4

How many sets of chromosomes do gametes have? How many in total?

Answer 4

1
1x 23 = 23

Question 5

If a triploid human could survive, each of its somatic cells would have how many chromosomes?

Answer 5

23 x 3 = 69

Question 6

What is packaged into chromosomes?

Answer 6

DNA

Question 7

What do chromosomes consist of?

Answer 7

Chromatin

Question 8

What is Chromatin?

Answer 8

Complex of DNA and protein that condenses during cell division

Question 9

What is the centromere?

Answer 9

Constriction that can be seen in the duplicated chromosome where sister chromatids are most closely attached

Question 10

Define the cell cycle

Answer 10

The cell grows during all 3 sub phases of interphase but chromosomes are duplicated only during the S phase

Question 11

What are the 3 sub phases of interphase?

Answer 11

G1, S and G2

Question 12

What happens in the G1 phase?

Answer 12

Metabolic activity and growth

Question 13

What happens in the S phase?

Answer 13

Metabolic activity, growth and DNA synthesis

Question 14

What happens in the G2 phase?

Answer 14

Metabolic activity, growth and preparation for cell division

Question 15

Describe the Mitotic phase of the cell cycle

Answer 15

Mitosis and cytokinesis occurs
Mitosis: Distribution of chromosomes into two daughter nuclei
Cytokinesis: Division of cytoplasm, producing two daughter cells. Each daughter cell can start a new cycle

Question 16

Describe Bacterial cell division by binary fission

Answer 16

1.Chromosomes replicate and rapidly move to the opposite ends of the cell by a mechanism involving an actin like protein
2. Replication continues and a new copy of the origin is at both ends of cell while the cell elongates
3. Replication finishes, the plasma membrane is pinched inwards by a tubulin like protein and a new cell wall is created
4. Two new daughter cells are made

Question 17

True or false: Prokaryotes evolved before eukaryotes

Answer 17

True

Question 18

Where did mitosis evolve from?

Answer 18

Most likely bacteria fission since the mitochondria and chloroplasts divide independently within eukaryotic cells through the use of binary fission

Question 19

What are the “checkpoints” in a cell cycle and what are they used for?

Answer 19

The cycle has specific checkpoints at which the cycle pauses until a go ahead signal is received. The G1, M and G2 checkpoints are the three that are the most well known

Question 20

What are the two types of regulatory proteins involved in cell cycle control?

Answer 20

Cyclins and Cyclin-dependent kinases (cdks)

Question 21

What is a limitation of the cyclin-dependent kinases

Answer 21

Their activity fluctuates during the cell cycle based on the concentration of its cyclin partner which controls cdk activity

Question 22

What does MPF stand for and its function

Answer 22

Stands for maturation promoting factor is a cyclin- Cdk complex that triggers a cell’s passage past the G2 checkpoint into M phase

Question 23

Why is the G1 checkpoint the most important?

Answer 23

If a cell receives the go ahead signal at G1 then it usually completes all the other phases and is able to divide

Question 24

What happens if the cell does not receive the go ahead signal at a checkpoint

Answer 24

Exits the cycle and enters a non dividing state called the G0 phase

Question 25

Why do some cells not pass the M checkpoint and enter anaphase

Answer 25

Their chromosomes have to be properly attached to spindle microtubules at their kinetochores. A molecular signal is released delaying anaphase until this process happens

Question 26

What is one factor that can influence cell division and give one example

Answer 26

Growth factors are released by certain cells to stimulate other cells to divide
Ex: Platelet derived growth factor (PDGF) made by platelets stimulate other cells to divide

Question 27

What is anchorage dependence

Answer 27

In animal cells, to divide they must be attached to a substratum

Question 28

What is density dependent inhibition

Answer 28

Cells stop dividing once they get too crowded

Question 29

Describe Cancer cells

Answer 29

Do not respond normally to body’s control mechanisms
May make their own growth factors
Have an abnormal cell cycle control system

Question 30

How are cancer cells made?

Answer 30

A normal cell is converted to a cancerous cell by a process called transformation. Cancer cells not eliminated by the immune system forms tumour

Question 31

Differentiate between benign and malignant tumours

Answer 31

Benign: abnormal cells remain only at the original site
Malignant: Invade surrounding tissues

Question 32

How does metastasis occur?

Answer 32

exporting of cancer cells to other
parts of the body, where they may form additional tumours

Question 33

What are 5 steps of mitosis

Answer 33

Prophase and pro-metaphase, metaphase, anaphase, telophase , cytokinesis

Question 34

What happens in prophase?

Answer 34

Chromatin condenses into visible chromosomes, each consisting of two sister chromatids joined at the centromere.
The nuclear envelope begins to break down.
The mitotic spindle starts to form from the centrosomes, which move to opposite poles of the cell.

Question 35

What happens in pro metaphase

Answer 35

The nuclear envelope completely disintegrates and chromosomes begin to move toward the cell’s equator

Question 36

What happens in metaphase

Answer 36

Chromosomes align along the metaphase plate and Spindle fibres are fully formed and attached to each sister chromatid.

Question 37

What happens in Anaphase

Answer 37

Sister chromatids are pulled apart by the spindle fibers toward opposite poles of the cell.
The centromeres split, allowing the chromatids to separate and become individual chromosomes.

Question 38

What happens in telophase

Answer 38

Chromosomes reach the poles and begin to de-condense back into chromatin

Question 39

What happens in cytokinesis

Answer 39

The cytoplasm divides, forming two separate daughter cells