3.2.2 All cells arise from other cells (not finished)

Question 1

State what the cell cycle is and outline its stages

Answer 1

Cycle of division with intermediate growth periods
1. interphase
2. mitosis or meiosis
3. cytokinesis

Question 2

Explain why the cell cycle does not occur in some cells

Answer 2

After differentiation some types of cell in multicellular organisms no longer have the ability to divide

Question 3

What is the difference between the cell cycle and mitosis

Answer 3

Cell cycle includes growth period between divisions, mitosis is only 10% of the cycle and refers only to nuclear division

Question 4

Outline what happens during interphase

Answer 4

G1 - cell synthesises proteins for replication and cell size doubles
S - DNA replicates = chromosomes consist of 2 sister chromatids joined at a centromere G2 - organelles divide

Question 5

State the purpose of mitosis

Answer 5

Produces 2 genetically identical daughter cells for
Growth
Repair
Asexual reproduction

Question 6

Name the stages of mitosis

Answer 6

Prophase
Metaphase
Anaphase
Telophase

Question 7

Outline what happens during prophase

Answer 7

Chromosomes condense, becoming visible
Centrioles move to opposite poles of cell and mitotic spindle fibres form
Nuclear envelope and nucleolus breaks down = chromosomes free in cytoplasm

Question 8

Outline what happens during metaphase

Answer 8

Sister chromatids line up at cell equator, attached to the mitotic spindle by their centromeres

Question 9

Outline what happens during anaphase

Answer 9

Requires ATP from hydrolysis
Spindle fibres contract
Sister chromatids separate into 2 distinct chromosomes and are pulled to opposite poles
Spindle fibres break down

Question 10

Outline what happens during telophase

Answer 10

Chromosomes decondense
New nuclear envelopes form around each set of chromosomes = 2 new nuclei each with 1 copy of each chromosome

Question 11

Root tip practical basic

Answer 11

Prepare a temporary mount of root tissue
Focus an optical microscope on the slide count the total number of cells in the fov and number of cells in mitosis
Calculate mitotic index

Question 12

How to prepare a temporary root tip mount

Answer 12

Place root tip in HCl to halt cell division
Stain root tip to see chromosomes
Macerate tissue in water using mounted needle
Use mounted needle to press down cover slip and obtain a single layer of cells

Question 13

Why is only the root tip used when calculating a mitotic index

Answer 13

Meristematic cells at root tip are actively undergoing mitosis
Cells further from root tip are elongating rather than dividing

Question 14

How cancer treatments control the rate of cell division

Answer 14

By disrupting cell cycle - Prevent DNA replication
Disrupt spindle formation = inhibit metaphase/anaphase

Question 15

Name a dye that binds to chromosomes

Answer 15

Toluidine blue

Question 16

Why are viruses classified as non living

Answer 16

They are acellular; no cytoplasm, no metabolism and cannot self replicate

Question 17

How do prokaryotic cells replicate

Answer 17

Binary fission
DNA loop replicates. Both copies stay attached to cell membrane. Plasmids replicate in cytoplasm
Cell elongates, separating the 2 DNA loops
Cell membrane contracts and septum forms
Cell cytoplasm splits into 2 identical progency cells, each with 1 copy of the DNA loop but with a variable number of plasmids