3.2.2 All cells arise from other cells

Question 1

Can all cells divide within multicellular organisms?

Answer 1

no

Question 2

Stages of the cell cycle

Answer 2

-interphase
(G1, S, G2)
-cell division
(mitosis (PMAT), cytokinesis)

Question 3

What stage of the cell cycle does DNA replication occur

Answer 3

-interphase

Question 4

Interphase stages

Answer 4

G1 (GAP PHASE 1- growth) phase

• cell growth
• organelles replicate

S (Synthesis) phase
- DNA replication

G2 (GAP PHASE 2) phase

• spindle protein copied
• growth continues

M phase - MITOSIS

Question 5

Mitosis

Definition

Answer 5

-mitosis is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication

Question 6

Stages of cell division

Answer 6

Interphase (G1, S, G2) 
Prophase
Metaphase
Anaphase
Telophase 
Cytokinesis

Question 7

Mitosis/cell division

Process (full)

Answer 7

INTERPHASE 
-DNA is replicated
└involving specific and complementary base-pairing
-organelles are replicated 
-ATP content is increased 

PROPHASE

• chromosomes shorten and thicken/condense
• and become visible
• they now consist of two chromatids
• joined by a centromere
• nuclear envelope breaks down

METAPHASE

• spindle forms
• the chromosomes line up at the middle/equator of the cell
• the centromere of the chromosomes attaches to spindle
• the centromere splits

ANAPHASE

• spindle fibres shorten
• sister chromatids separate
• and move to opposite poles of the cell

CYTOKINESIS

• chromosomes uncoil
• nuclear envelope reforms

Question 8

What is interphase

Answer 8

Preparation for cell division

Question 9

Interphase

Answer 9

-DNA is replicated
└involving specific and complementary base-pairing
-organelles are replicated
-ATP content is increased

Question 10

Prophase

Answer 10

• chromosomes shorten and thicken/condense
• and become visible
• they now consist of two chromatids
• joined by a centromere
• nuclear envelope breaks down

Question 11

Metaphase

Answer 11

• spindle forms
• the chromosomes line up at the middle/equator of the cell
• the centromere of the chromosomes attaches to spindle

Question 12

Anaphase

Answer 12

• the centromere splits
• spindle fibres shorten
• sister chromatids separate
• and move to opposite poles of the cell

Question 13

Telophase

Answer 13

• chromosomes uncoil

- nuclear envelope reforms

Question 14

Role of the centromere in mitosis

Answer 14

• holds chromatids together
• attaches chromatids to spindle
• allows chromatids to be separated and move to opposite poles in anaphase

Question 15

Mitosis products

Answer 15

-two genetically identical daughter cells

Question 16

Importance of mitosis

Answer 16

-growth
-replacing cells and repairing tissues
-asexual reproduction /cloning
└produces genetically identical cells
-maintains chromosome number in all cells

Question 17

EQ: During stage S, the genetic information is copied and checked.
Suggest what might happen if the genetic information is not checked

Answer 17

• there may be a mutation or error in copying so faulty DNA produced
• and daughter cells will not receive identical genetic information
• so the daughter cells do not function/are not produced

Question 18

EQ: Explain why the DNA in two sister chromatids is identical

Answer 18

-semi-conservative replication
- double helix unwinds
-strands unzip
-hydrogen bonds break between complementary bases in the polynucleotide strands
└using DNA helicase
-both strands act as a template
-free DNA nucleotides align
-complimentary base pairing occurs
- C to G (3 H bonds) and T to A (2 H bonds)
- hydrogen bonds reform
└DNA polymerase joins adjacent nucleotides in the condensation reaction
- sugar-phosphate back bone forms
└using phosphodiester bonds

Question 19

EQ: How can you investigate Mitosis?

Answer 19

• stain a tip from a growing root
• add HCL
• put it in a water bath
• place a cover slip over
• push firmly to make it thinner
• now you can see it under a microscope

Question 20

EQ: Mitotic index=

Answer 20

number of cells with visible chromosome/ total number of cells observed

Question 21

Role of spindle fibres

Answer 21

• they attach to the centromeres of chromosomes in metaphase

- and they shorten and pull the sister chromatids to opposite poles in anaphase

Question 22

Cytokinesis

Definition

Answer 22

• the division of the cytoplasm in mitosis

- produces two new genetically identical daughter cells

Question 23

How is mitosis different to cytokinesis?

Answer 23

• mitosis is nuclear division producing two identical nuclei

- cytokinesis is cellular division producing two identical cells

Question 24

What type of process is mitosis

Answer 24

A controlled process

Question 25

How is mitosis a controlled process

Answer 25

Mitosis and the cell cycle are controlled by a number of genes

Question 26

What can uncontrolled cell division lead to

Answer 26

the formation of tumours and of cancers

Question 27

How is cancer the result of uncontrolled cell division?

Answer 27

Mitosis and the cell cycle are controlled by genes. - normally, when cells have divided enough times to make enough new cells, they stop - if there's a mutation in a gene that controls cell division, the cells can grow out of control - cells keep on dividing and form tumours - cancer is a tumour that invades surrounding tissue

Question 28

Cancer treatment areas

Answer 28

- controlling rate of cell division - prevent DNA replication - interfere with spindle formation in metaphase

Question 29

What are 2 cell cycle targets of cancer treatments?

Answer 29

-Gl (cell growth and protein production) └some chemical drugs in chemotherapy prevent the synthesis of enzymes needed for DNA replication, so the cell is unable to enter the synthesis phase (S), disrupting the cell cycle and forcing the cell to kill itself -S phase (DNA replication) └radiation and some drugs damage DNA. At several points in the cell cycle (including just before and during S phase) the DNA in the cell is checked for damage. If severe damage is detected, the cell will kill itself -preventing further tumour growth

Question 30

How do prokaryotic cells replicate

Answer 30

Binary fission

Question 31

Binary fission | Process

Answer 31

-the circular DNA and plasmids replicate └the main DNA loop is only replicated once but plasmids can be replicated may times -the cell gets bigger -the DNA loops moved to opposite poles of the cell. -the cytoplasm begins to divide -new cell walls begin to form -the cytoplasm divides └two daughter cells are produced └each daughter cell has one copy of the circular DNA but can have a variable number of copies of the plasmids

Question 32

Binary fission | Products

Answer 32

-two new daughter cells -each cell has one copy of circular DNA └variable number of plasmids

Question 33

Similarities between mitosis and binary fission

Answer 33

- chromosome DNA is replicated - cytokinese occurs - daughter cells have the same genetic information - division of cytoplasm

Question 34

Differences between mitosis and binary fission

Answer 34

- binary fission has: - has no organelle - no interphase - no spindle fibres

Question 35

How do viruses undergo cell division

Answer 35

-viruses do not undergo cell division | └as they are non-living

Question 36

Virus replication

Answer 36

- viruses use their attachment proteins to bind to complimentary receptor proteins on the surface of host cells - their genetic information is injected into the host cell - genetic material and proteins are replicated by host cell machinery - viral components assemble - replicated viruses are released from host cell

Question 37

How does the virus damage the host cell?

Answer 37

The replicated viruses build up inside the cell until they overtake the cell and it bursts, destroying the host cell. -the viruses are then free to infect other cells.

Question 38

What do viruses need to divide and why?

Answer 38

As viruses are acellular and non-living, they have no metabolic processes of their own. They cannot replicate without a host cell.

Question 39

Describe how viruses enter host cells.

Answer 39

- the attachment proteins attach to complimentary receptors on the surface of the cell - the capsid fuses with the cell membrane and the nucleic acid DNA of the virus is injected into the host cell, where it enters the nucleus

Question 40

What is the process of viral replication called?

Answer 40

-the lytic cycle | └because it results in the lysis of the host cell