3.2.2 All Cells Arose From Other Cells (mitosis)

Question 1

Stages of mitosis

Answer 1

I(interphase)
Pissed (prophase)
Myself (metaphase)
At (anaphase)
Tescos (telophase +cytokensis)

Question 2

What happens in interphase

Answer 2

DNA replicates (semi conservatory)
Leaving 2 chromatids joined at the centromere

No of organelles and volume of cytoplasm increases (protein synthesis)

Question 3

What happens in prophase

Answer 3

-chromosomes condense becoming shorter and thicker, they appear as 2 sister chromatids joined by a centromere

-nuclear envelope breaks down

-centrioles move to opposite poles forming spindle network

-spindle fibers attach to chromosomes by the centromeres

Question 4

Metaphase

Answer 4

Spindle fibres are attached and the chromosome align along the equator

Question 5

Anaphase

Answer 5

Spindle fibres contract, pulling the chromatdids to opposite poles
(Centromere divides)

Question 6

Telophase

Answer 6

Chromosomes uncoil becoming thicker and longer
Nuclear envelope reforms (2 nuclei)
Spindle fibers/centrioles break down

Question 7

Cytokensis

Answer 7

Cytoplasm and cell membrane divides

Forms to genetically identically daughter cells

Question 8

Why do some cells not divide

Answer 8

Not all cells have the ability (neurone)

Question 9

Importance of mitosis

Answer 9

Growth
Repair
Asexual reproduction

Question 10

How can tumours and cancers form

Answer 10

Mutations in the genes controlling mitosis leads to uncontrolled cell division

Tumours formed if this result in a mass of abnormal cells:
-malignant if cancerous (can spread)
-begin if non cancerous

Question 11

How do treatments control rate of division

Answer 11

Some distrust spindle fibre activity so chromosomes don’t:
-attach to spindle
-chromatids can’t separate
-prevents/slows mitosis

Some prevent DNA replication (interphase)

-can’t make 2 copies of chromosomes
-prevents or slows mitosis

Question 12

Describe how prokaryotic cells replicate

Answer 12

By binary fission:
-replication of circular DNA
-Replication of Plasmids
-divisions of cytoplasm to produce 2 daughter cells, each with a copy of circular DNA and many copies of the plasmids

Question 13

How do viruses replicate

Answer 13

Attachment proteins attach to complementary receptors in host cells

Inject viral nucleic acid (DNA/RNA) into host cells

Infected host cell replicate viruses particles:
-nucleic acid is replicated
-cells produced viral proteins/enzymes/capsules
-virus assembles then released

Question 14

What is the mitotic index (MI)

Answer 14

Proportion of cells undergoing mitosis (with visible chromosomes)

MI=number of cells undergoing mitosis divided by total of cells in a sample