All Cells Arise From Other Cells

Question 1

What is cell division for?

Answer 1

• replace old, dying or dead cells in eukaryotes

- for growth of an organism

Question 2

What is the cell cycle?

Answer 2

A sequence of events that occurs during cell division as one parent cell divides to form 2 genetically identical daughter cells

Question 3

What are the 3 phases of the cell cycle?

Answer 3

• interphase
• mitosis
• cytokinesis

Question 4

What are the 3 stages of interphase?

Answer 4

G1
S
G2

Question 5

What happens in G1 of interphase?

Answer 5

• cell grows + makes a new set of organelles and proteins for the daughter cells

Question 6

What happens in S of interphase?

Answer 6

• cellular DNA is replicated + the 2 daughter cell each get one set of DNA

Question 7

What happens in G2 of interphase?

Answer 7

• cell growth continues + there is synthesis of special proteins in preparation for mitosis

Question 8

What is mitosis?

Answer 8

Mechanism of cell division that occurs in somatic cells

Question 9

What is meiosis?

Answer 9

Cell division process that occurs only in gametes

Question 10

Characteristics of chromosomes in humans

Answer 10

• 23 pairs
• diploid organisms so 2 sets of each chromosome
• large structure of DNA + proteins
• made up of 2 chromatids held together by a centromere

Question 11

What is each copy of a particular chromosome called?

Answer 11

A chromatid

Question 12

What do histones result in?

Answer 12

DNA wrapped around histones results in chromatin which coils into chromosomes

Question 13

What are the 4 stages of mitosis?

Answer 13

Prophase
Metaphase
Anaphase
Telophase

Question 14

What happens in prophase of mitosis?

Answer 14

• chromosomes become shorter + thicker and become visible as sister chromatids
• centrioles split + move to opposite poles of the cell + produce mitotic spindle which extends across the cell
• nuclear envelope disintegrates + chromosomes are freed into the cytoplasm

Question 15

What happens in metaphase of mitosis?

Answer 15

• nuclear envelope is completely gone
• spindle fibres attach to the centromeres of each chromosome
• spindle fibres pull the chromosomes lining them up at the equator/metaphase plate

Question 16

What happens in anaphase of mitosis?

Answer 16

• chromosomes break apart at the centromere
• spindle fibres begin pulling the sister chromatids to opposite poles of the cell
• form 2 v-shaped chromatid structures

Question 17

What happens in telophase of mitosis?

Answer 17

• spindle fibres pull chromatids to opposite poles of the cell
• chromatids uncoil
• nuclear envelope reforms around each set of chromosomes
• cell now has 2 nuclei each with a full set of identical DNA
• prepares to split + forms a cleavage furrow

Question 18

What happens in cytokinesis?

Answer 18

• final step of mitosis
• cell will completely divide into 2 daughter cells
• each daughter cell is identical to each other and their parent cell

Question 19

Why do cells have checkpoints in cell division?

Answer 19

Because a mutation could have formed so transitions from one phase to the next are highly regulated by checkpoints

Question 20

What happens if the cell is damaged during the cell cycle?

Answer 20

The cell will try to repair the damage by stopping the cell cycle, if its irreversible apoptosis happens

Question 21

What are the checkpoints regulated by?

Answer 21

Cyclins and cyclin dependent kinases which monitor the rate of progression through the cell cycle as well as tumour suppressor proteins which check for mutations

Question 22

Why is apoptosis important?

Answer 22

Since it prevent mutations from being passed down

Question 23

What 2 mutations can cause cancer?

Answer 23

• mutant tumour suppressor gene

- mutant oncogene

Question 24

Why can a mutant tumour suppressor gene cause cancer?

Answer 24

• cannot prevent a mutated cell from carrying out cell division and growing

Question 25

Why can a mutant oncogene cause cancer?

Answer 25

• oncogenes promote cell division + growth

- so a mutant oncogene will force cell to rapidly divide + proliferate

Question 26

What are tumours?

Answer 26

• group of rapidly growing cancer cell which forms a rapidly growing tissue
• unable to control their growth
• acquire even more mutations as they grow so become more uncontrollable

Question 27

Why can tumours be lethal?

Answer 27

• outcompete nutrients to fuel their growth

- if organs can’t obtain necessary nutrients they stop functioning + eventually die

Question 28

What are some treatment dangers with cancer?

Answer 28

• non-specific since it targets all fast growing cells including hair, gut & skin
• very toxic in high doses so needs to be limited
• mutagenic + can result in the formation of new cancers

Question 29

What parts of the cell cycle does chemotherapy usually target?

Answer 29

• G1 + prevent protein/enzyme synthesis
• DNA replication
• mitosis (e.g prevent spindle fibres from forming)