THE VARIETY OF LIVING ORGANISMS

The Cell Cycle : Remember it! & Test it!

The Cell Cycle : Remember it! & Test it!

  • Before a cell can divide by mitosis the DNA needs to replicate first.
  • DNA replication occurs in the interphase stage and involved semi-conservative replication in which each strand of DNA is copied separately.
  • DNA replication involves a number of enzymes which break the strands apart and create the new strands.
  • Mitosis in the process in which identical cells are created that contain the same genetic information as the original cell.
  • Mitosis is made up of five stages.
  • In the last stage, cytokinesis, the cell physically separate.

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TEST IT!

1.

The diagram below shows the cell cycle of mitosis.

a. Complete the table below about the number of chromosomes and mass of DNA in the nucleus during mitosis.

Nucleus

Number of chromosomes

Mass of DNA

At prophase

26

60

At telophase

b. DNA mutations can cause cancer however there are drugs that are used to treat the disease. At what phase of the cycle would:
i. a drug act which prevented the DNA from replicating?
ii. a drug act that prevented the spindle fibres from shortening?

2. DNA replication involves a number of enzymes.
a. Name the enzyme which carries out each of the following:
i. breaks the hydrogen bond _________________________________
ii. creates a complementary strand ____________________________
iii. creates an RNA primer
b. Name and describe the form of division used in DNA replication.

3. Mitosis and meiosis are both types of cell division in the body.
a. Explain the difference between the two types of cell division.
b. Give two reasons for mitotic cell division in the body.
i. _____________________________________________________
ii. _____________________________________________________
c. Cytokinesis is where the daughter cells separate. How is this stage different in animal and plant cells?

ANSWERS

1.
a.

Nucleus

Number of chromosomes

Mass of DNA

At prophase

26

60

At telophase

13

15

b.
i. interphase
ii. anaphase

2. a.
i. DNA helicase
ii. DNA polymerase
iii. RNA polymerase
b. Semi-conservative replication: the DNA molecule of the parents splits into its two strands and each strand is copied.

3. a. Mitosis creates exact copies of the diploid parent cell. Meiosis creates daughter cells which contain half the amount of genetic information (haploid cells).
b.
i. growth
ii. repair
c. In animal cells, the cell membrane creates a cleavage furrow which pinches apart. In plant cells, a cell plate is formed which forms the new cell wall of the daughter cells.