3.2.2 All cells arise from other cells

Question 1

What happens in G1 during interphase?

Answer 1

The cytoplasm grows and additional organelles are synthesised.

Question 2

What happens in S phase during interphase?

Answer 2

The DNA is replicated.

Question 3

What happens in G0?

Answer 3

The cells exit the cell cycle and stop dividing.

Question 4

Describe the cell cycle.

Answer 4

• DNA is replicated in S-phase of interphase.

• Prophase - Chromosomes condense and become visible, nuclear envelope disintegrates.

• Metaphase - Chromosomes line up at the equator of the cell.

• Anaphase - Sister chromatids are pulled to the opposite poles of the cell.

• Telophase - Chromosomes decondense and the nuclear envelope starts to reform around the two nuclei.

• Cytokinesis - The cytoplasm and surface membrane splits forming two new cells that are genetically identical (sister cells).

Question 5

Describe HIV replication.

Answer 5

• HIV attachment proteins are complementary to the receptors on the helper T cell.

• Viral nucleic acid enters the cell.

• Reverse transcriptase converts RNA to DNA and inserted into the host genome.

• DNA is transcribed and the HIV capsid (protein) and enzymes are made by host cell ribosomes.

• Everything is assembled by the host cells RER and Golgi apparatus into new virus protein, capsid, enzymes.

• Cell lyses and viruses are released.

Question 6

Describe and name the process by with prokaryotes and bacteria replicate.

Answer 6

• Bacteria and prokaryotes reproduce by binary fission.

• First the DNA( and plasmids) are replicated.

• Then the cytoplasm and cell membrane divides in two producing two daughter cells.

• Each daughter receives one copy of the circular DNA (and variable number of plasmids if present).

• Circular DNA can replicate once while plasmids can replicate multiple times.