Cell Cyles, Mitosis/ Meiosis And Binary Fission

Question 1

What is the eukaryotic cell cycle?

Answer 1

Interphase (G1, S, G2)

Mitosis/meiosis

Cytokinesis

Question 2

What happens during G1 of interphase?

Answer 2

Organelle replication
Increase in the cell size
Biosynthesis

Question 3

What does the checkpoint between G1 and S phase ensure?

Answer 3

Ensures the cell is ready to enter S phase
Some cells triggered by the checkpoint may enter G0 ( apoptosis or cell death)

The cell cycle cannot be reversed so DNA replication can only happen once per cell cycle.

Question 4

What happens during S phase?

Answer 4

DNA replication
Commits the cell to complete the cell cycle
Rapid

Question 5

What happens during G2 phase of interphase?

Answer 5

The cells grow

Chloroplast and mitochondria DNA replicates

Question 6

What does the checkpoint between G2 and mitosis/ meiosis ensure?

Answer 6

Stimulates spindle forming proteins

Triggers condensation of chromatin (components of material in a chromosome)

Question 7

How is the cell cycle regulated?

Answer 7

Via checkpoints

These ensure cell division is controlled and detect any damage to the DNA which may causes genetic disorders

Question 8

What are the stages of mitosis?

Answer 8

Prophase
Metaphase
Anaphase
Telophase

Cytokinesis

Question 9

What happens during prophase of mitosis?

Answer 9

DNA supercooling
Nuclear envelope breaks down
Centrioles divide and new centrioles move to the poles
Spindle fibres form

Question 10

What happens during metaphase of mitosis?

Answer 10

Sister chromatid pairs attach to spindle via their centromeres.

The chromatid pairs line up along the equator of the cell

Question 11

What happens during anaphase of mitosis?

Answer 11

Centromere of each chromatid pair splits

Motor proteins drag the chromatids towards the poles

Question 12

What happens during telophase of mitosis?

Answer 12

New nuclear envelopes form around the chromosomes

Cell contains two nuclei

Question 13

What happens during cytokinesis?

Answer 13

The cell splits forming two genetically identical daughter cells.

Question 14

Why is meiosis important?

Answer 14

Important for sexual reproduction and to increase genetic variation
( through random fertilisation)

Question 15

What is a diploid cell?

Answer 15

Cell that contains two sets of chromosomes

2N

Question 16

What is a haploid cell?

Answer 16

Half the number of chromosomes as a diploid cell

N

Question 17

Define homologous chromosome

Answer 17

One chromosome from mother and one from the father but they both code for the same gene with the same loci

Question 18

Define sister chromatid?

Answer 18

Genetically identical but 2 together form 1 chromosome

Question 19

What are the products from mitosis and meiosis?

Answer 19

Mitosis:
Produces 2 genetically identical diploid cells

Meiosis:
Produces 4 haploid cells not genetically identical

Question 20

What are the stages in meiosis?

Answer 20

Prophase I
Metaphase I
Anaphase I
Telophase I

Prophase II
Metaphase II
Anaphase II
Telophase II

Cytokinesis

Question 21

What happens during prophase I of meiosis?

Answer 21

Super coiling and compacting of chromosomes

Spindle formation

Question 22

What happens during metaphase I of meiosis?

Answer 22

Homologous chromosomes line up next to each other at the equator of the cell(independent assortment) where some may be crossed over

Question 23

What happens during anaphase I of meiosis?

Answer 23

Allele reshuffling

Chromosomes pulled to the poles of the cell

Question 24

What happens during telophase I of meiosis?

Answer 24

Nuclear envelopes reform

Question 25

What happens during prophase II of meiosis?

Answer 25

Nuclear envelopes break down Super coiling and DNA condenses Spindles reform

Question 26

What happens during metaphase II of meiosis?

Answer 26

Single chromosomes line up on each spindle fibre at the equator of the cell. Random assortment of chromatids

Question 27

What happens during anaphase II of meiosis?

Answer 27

Centromeres divide Individual chromatids are pulled to each pole

Question 28

What happens during telophase II of meiosis?

Answer 28

Nuclear envelope reforms around all f haploid clusters

Question 29

What happens during cytokinesis in meiosis?

Answer 29

He cell divides into 4 non genetically identical haploid cells.

Question 30

What is binary fission?

Answer 30

The process by which prokaryotic cells divide

Question 31

What are the stages in binary fission?

Answer 31

1. Circular DNA molecules replicate and both copies attach to the plasma membrane. Plasmids also replicate 2. Plasma membrane between the pole begins to grow and elongate 3. Pinching occurs at the equator of the cell 4. New cell walls form between the 2 DNA molecules and 2 daughter cells are produced Numbers of plasmids may vary as there is no guarantee of even distribution

Question 32

What are viruses?

Answer 32

A cellular non living particles (not cells) which are parasitic and live of host cells.

Question 33

How do viruses replicate?

Answer 33

1. Attach to host cells via attachment proteins 2. Insert genetic material (DNA, ssRNA, dsRNA) into host cells. 3. Host cell Machinery reads these instructions and manufacturers viral components 4. These are assembled into virons (viral particles) which then get egressed/released into the host body