All Cells Arise From Other Cells

Question 1

What is the structure of a chromosome like?

Answer 1

Either a single chromosome (looks like a single wotsit)

Or

1 chromosome can be made from 2 sister chromatids joined at a centromere (two wotsits back to back)

Question 2

What are the different aspects of a chromosome?

Answer 2

Chromatid
Telomere (bottom of chromosome)
Gene in a particular locus
Non coding region

Question 3

How many pairs of chromosomes and pairs of chromosomes does a human have?

Answer 3

46 chromosomes
23 pairs of chromosomes

1/2 from each parent

Question 4

What must happen before a cell can divide?

Answer 4

Organelles must replicate
DNA must replicate
The cell must grow

Question 5

What cell division is used generally?

Answer 5

Mitosis

Question 6

What is mitosis important for?

Answer 6

Growth of new cells
Repair of damaged tissues
Asexual reproduction

Question 7

What are the stages of the cell cycle?

Answer 7

Interphase
Prophases
Metaphase
Anaphase
Telophase
Cytokinesis

Question 8

Describe the overview of what happens in interphase?

Answer 8

Cell actively synthesises proteins chromosomes are invisible
DNA replicates

The cell membrane, nuclear envelope, nucleolus and cytoplasm is still present

Question 9

What are the stages of interphase?

Answer 9

G1- first growth phase
S- Synthesis phase
G2- second growth phase

Question 10

What happens in the growth phases G1 and G2 of interphase?

Answer 10

Organelles are synthesised and biochemicals are produced

In G2- energy stores are increased to supply 2 daughter cells being formed from one parent

Question 11

What happens in the S phase of interphase?

Answer 11

DNA is replicated

Question 12

What happens in prophase?

Answer 12

Chromosomes become visible as they become shorter, denser and darker as a result (no longer stringy)
The nuclear envelope disintegrates
Nucleolus disappears

Question 13

What happens in metaphase?

Answer 13

The chromosomes line up on the equator of the cell with the help from spindle fibres

Question 14

What happens in anaphase?

Answer 14

The chromatids separate down the middle and move to the opposite pole as the spindle fibres attached contract
The spindle fibres start to become less visible (disappearing)

Question 15

What happens in telophase?

Answer 15

Chromatids reach the poles and become indistinct
The nuclear envelope and nucleolus starts to reform
Spindle disintegration
The cell start to split in the middle

Question 16

What happens in cytokinesis?

Answer 16

The cytoplasm divided producing two new cells containing chromosomes in each

Question 17

What are spindle fibres made of?

Answer 17

Actin and myosin

Question 18

What are spindle fibres held in place by?

Answer 18

Centrioles (situated at the poles)

Question 19

What is generally the longest phase of mitosis?

Answer 19

Interphase

Question 20

How do you calculate the length of cell division?

Answer 20

Work out the percentage of cells in the required phase(s)
Work out the percentage of the time given for the phase(s) from the tine it takes for a full cycle
I.e
(12/150)x 100 =8%
8% of 16.8 hours = 1.34 hour

Question 21

What is the mitotic index?

Answer 21

The proportion of cells in a tissue sample that are undergoing mitosis

Question 22

What should the answer for mitotic index be in?

Answer 22

0 to 1

Or

0% to 100%

Question 23

How to work out the mitotic index?

Answer 23

Number of cells with visible chromosomes
Divided by
Total number of cells observed

Question 24

What can occur as a result of uncontrolled cell division?

Answer 24

Cancer-tumours

Question 25

What is the hayflick limit?

Answer 25

A limited time that a cell can under go mitosis

Question 26

How does the hayflick limit relate to cancer?

Answer 26

Cancer cells (as well as stem cells) don't have limit of going through mitosis

Question 27

What are some causes of cancer?

Answer 27

``` Carcinogens UV Exposure Radiation exposure Genetic disposition Random Age ```

Question 28

Who is cancer more common in? Why?

Answer 28

Older people | Their somatic cells (body cells) accumulate mutations

Question 29

What happens if gametes mutate?

Answer 29

They are passed onto the next generation

Question 30

How can cancer spread to secondary tumours?

Answer 30

If the tumour cells squeeze into the blood or lymphatic vessels Via the blood tumour cells can adhere to blood vessel walls to form distant metastases Via the lymph they can metastasise in the lymph node

Question 31

What is a benign tumour?

Answer 31

Enclosed in a capsule and doesn't invade surrounding tissues | Grows in the centre of the capsule

Question 32

What is a malignant tumour?

Answer 32

Grows at the edges, invading surrounding tissues and organs | Cells may break off and form secondary tumours elsewhere

Question 33

What happens when a tumour metasises?

Answer 33

Tumours form in other places from the original tumour

Question 34

What are the treatments for cancer?

Answer 34

Chemotherapy Radiotherapy Surgery

Question 35

What are the advantages and disadvantages of chemotherapy?

Answer 35

Shrink the tumour or slow the growth Can relieve symptoms Chemicals can poison healthy cells Your immune system is wiped out

Question 36

What are the advantages and disadvantages of radiotherapy?

Answer 36

Large portions of cancer cells are killed Shrinks the tumour and relieves the mass Damage to surrounding tisue Cant kill cancer cells not seen on scan

Question 37

What are the advantages and disadvantages of surgery?

Answer 37

Most effective at resection Symptoms relieved Risk- bleeding, infection, anaesthetic Recovery time with potential side effects

Question 38

How does a prokaryotic bacterial cell replicate?

Answer 38

The cell grows organelles and replicates the DNA The bacteria lengthens and the DNA moves further apart to opposite ends of the cell The centre of the bacteria contracts starting to separate the cell A cell membrane and cell wall is formed across the cytoplasm The cell separates into two daughter bacterial cells

Question 39

How do viruses replicate?

Answer 39

The virus attaches to a cell The virus is engulfed by endocytosis Viral contents are released, RNA enters the nucleus where it is replicated by the viral RNA polymerase Viral RNA is used to make viral proteins New virul proteins are released into the extracellular fluid The cell not killed continues to make a new virus