3.2.2 All cells arise from other cells

Question 1

Within multicellular organisms, do all cells retain the ability to divide?

Answer 1

No, not all cells retain the ability to divide.

Question 2

What type of cells in multicellular organisms retain the ability to divide?

Answer 2

Eukaryotic cells that show a cell cycle retain the ability to divide.

Question 3

During which phase of the cell cycle does DNA replication occur?

Answer 3

DNA replication occurs during interphase.

Question 4

What is mitosis?

Answer 4

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

Question 5

What happens to chromosomes during interphase?

Answer 5

Chromosomes are not visible; DNA replicates and protein synthesis occurs.

Question 6

What happens to chromosomes during prophase?

Answer 6

Chromosomes condense and become visible. The nuclear envelope breaks down, and spindle fibres begin to form.

Question 7

What happens to chromosomes during metaphase?

Answer 7

Chromosomes line up at the equator of the cell and attach to spindle fibres by their centromeres.

Question 8

What happens to chromosomes during anaphase?

Answer 8

Sister chromatids are separated as spindle fibres pull them to opposite poles of the cell.

Question 9

What happens to chromosomes during telophase?

Answer 9

Chromatids reach opposite poles, decondense into chromatin, and nuclear envelopes reform around each set of chromosomes.

Question 10

What is cytokinesis?

Answer 10

Cytokinesis is the division of the cytoplasm, producing two new cells.

Question 11

What is the role of spindle fibres in mitosis?

Answer 11

Spindle fibres attach to centromeres and separate chromatids by pulling them to opposite poles.

Question 12

What are the stages of the cell cycle?

Answer 12

Interphase, prophase, metaphase, anaphase, telophase (including cytokinesis).

Question 13

What is mitosis described as a controlled process?

Answer 13

Mitosis is controlled to ensure correct cell division; uncontrolled cell division can lead to tumours and cancers.

Question 14

How do many cancer treatments work?

Answer 14

Many cancer treatments control the rate of cell division.

Question 15

What is binary fission?

Answer 15

Binary fission is the process by which prokaryotic cells divide, involving replication of circular DNA and plasmids, and division of the cytoplasm to produce two daughter cells.

Question 16

What do daughter cells produced by binary fission contain?

Answer 16

Each daughter cell contains a single copy of circular DNA and a variable number of plasmid copies.

Question 17

Why do viruses not undergo cell division?

Answer 17

Viruses are non-living and rely on the infected host cell to replicate their virus particles after injecting their nucleic acid.

Question 18

Describe binary fission in bacteria. (3)

Answer 18

1. Replication of (circular) DNA;
   Accept nucleoid
   Reject chromosome
   Reject mitosis
2. Replication of plasmids;
3. Division of cytoplasm (to produce daughter cells);
   Ignore genetically identical

Question 19

Describe and explain the arrangement of the genetic material shown in prophase.

Answer 19

1. Chromosomes (are) becoming visible/distinct;
2. Because (still) condensing;

Question 20

Name the process by which bacterial cells divide.

Answer 20

Binary fission;

Question 21

Describe the appearance and behaviour of chromosomes during prophase.

Answer 21

1. Chromosomes coil / condense / shorten / thicken / become visible;
2. (Chromosomes) appear as (two sister) chromatids joined at the
   centromere;

Question 22

Describe the appearance and behaviour of chromosomes during metaphase.

Answer 22

1. Chromosomes line up on the equator / centre of the cell;
2. (Chromosomes) attached to spindle fibres;
3. By their centromere;

Question 23

Describe the appearance and behaviour of chromosomes during anaphase.

Answer 23

1. The centromere splits / divides;
2. (Sister) chromatids / chromosomes are pulled to opposite poles /
   ends of the cell / separate;

Question 24

Describe the appearance and behaviour of chromosomes during telophase.

Answer 24

Chromatids / chromosomes
uncoil / unwind / become longer / thinner.