All cells arise from other cells

Question 1

How do eukaryotic cells divide?

Answer 1

By mitosis

Question 2

How do prokaryotic cells divide?

Answer 2

By binary fission

Question 3

How do viruses replicate?

Answer 3

Inside a host cell

Question 4

What are the 3 key stages of the cell cycle?

Answer 4

Interphase (G1, S, G2), Nuclear division(mitosis or meiosis), Cytokinesis.

Question 5

Describe interphase.

Answer 5

The longest stage of the cell cycle consisting of G1, S and G2. The cell grows in size and organelles double (G1). The DNA also replicates in S phase.

Question 6

Describe nuclear fission.

Answer 6

Is either mitosis or meiosis. In mitosis it would create 2 identical diploid cells whereas in meiosis it would create 4 non identical haploid cells.

Question 7

What are the stages in mitosis?

Answer 7

Prophase, Metaphase, Anaphase, Telophase

Question 8

What is the purpose of mitosis?

Answer 8

For growth and repair such as the clonal expansion of B cells

Question 9

How many rounds of division occur in mitosis?

Answer 9

1

Question 10

What is a centromere?

Answer 10

The point in the middle of a chromosome that holds the two chromatids together.

Question 11

What kind of cells are made by mitosis?

Answer 11

Genetically identical diploid cells

Question 12

Explain prophase.

Answer 12

The chromatid condense into chromosomes and become visible. In animal cells, the centrioles will move to opposite poles of the cell. The centrioles are responsible for creating the spindle fibres. The nucleolus also disappears.

Question 13

Explain metaphase.

Answer 13

There is no nucleus. The chromosomes align along the equator of the cell. The spindle fibres release from the poles and attach to the centromere and chromatid.

Question 14

Explain anaphase.

Answer 14

• The spindle fibres retract and pull the centromere and sister chromatid to opposite poles of the cell.
• This causes the centromere to divide in two.
• Separate chromatids are now chromosomes
• This stage requires energy in the form of ATP provided by respiration in the mitochondria.

Question 15

Explain telophase.

Answer 15

The chromosomes are now at opposite poles of the cell and become longer and thinner. The spindle fibres break down and the nucleus starts to reform.

Question 16

Explain cytokinesis

Answer 16

Cytoplasm splits and we end up with two new genetically identical cells.

Question 17

What is the mitotic index equation?

Answer 17

number of cells in mitosis / number of cells

Question 18

Explain binary fission in prokaryotes.

Answer 18

1. DNA and plasmids replicate
2. The circular DNA strands move to opposite poles
3. The cytoplasm divides to produce 2 genetically identical daughter cells each with a single copy of the circular DNA and a variable number of copies of plasmids.