Comprehension

Question 1

Herpes simplex virus (HSV) infects nerve cells in the face, including some near the lips. Like many other viruses, HSV can remain inactive inside the body for years. When HSV becomes active, it causes cold sores around the mouth.
Human cells infected with a virus may undergo programmed cell death. While HSV is inactive inside the body, only one of its genes is transcribed. This gene is the latency-associated transcript (LAT) gene that prevents programmed cell death of an infected nerve cell.
Scientists have found that transcription of the LAT gene produces a microRNA.
This microRNA binds to some of the nerve cell’s own mRNA molecules. These mRNA molecules are involved in programmed cell death of nerve cells. The scientists concluded that production of this microRNA allows HSV to remain in the body for years.

Answer 1

Read the extract above

Question 2

HSV infects nerve cells in the face. Explain why it infects only nerve cells.

Answer 2

HSV has antigens on its surface. These antigens are only have a complementary shape to specific receptors found on nerve cells.

Question 3

HSV can remain inactive inside the body for years. Explain why this virus can be described as inactive.

Answer 3

Because it would show no symptoms (cold sores) because the virus won’t be replicating.

Question 4

Suggest one advantage of programmed cell death

Answer 4

Prevents viral replication

Question 5

The scientists concluded that production of this microRNA allows HSV to remain in the body for years.
Explain how this microRNA allows HSV to remain in the body for years.

Answer 5

microRNA binds to RNA through complementary base pairing. This affects the gene that causes programmed cell death. This means that the gene will no longer be able to be transcribed as ribosomes cannot read it the mRNA it is derived from. This prevents apoptosis.