STIs

Question 1

What is a provirus?

Answer 1

a virus that inserts its DNA into the chromosomes of the host cell
it replicates every time the host cell divides
it can stay dormant for a long time before becoming active

Question 2

How is chlamydia spread?

Answer 2

through contact with sexual fluid from an infected partner

an infected mother can pass chlamydia to her baby during birth

Question 3

How is HIV spread?

Answer 3

• through unprotected sex with an infected partner
• sharing needles with an infected person
• transmission from mother to foetus
• infection from blood products

Question 4

How can STIs be reduced/prevented?

Answer 4

• using condoms
• screening people, including pregnant women (free tests)
• screening blood transfusions
• supplying drug users with sterile needles
• treated infected people using antibiotics

Question 5

What is an STI?

Answer 5

sexually transmitted infection

Question 6

Describe the virus lifecycle

Answer 6

viruses infect host cells and multiply by the lytic/lysogenic cycle

• virus attaches to host cell
• virus enters cell
• DNA/RNA is injected into the cell
• the virus RNA/DNA copies itself
• new virus proteins are made using the organelles in the host cell
• DNA/RNA virus proteins are packaged together to make new viruses
• viruses are released from the cell, usually destroying the host cell

Question 7

State what STIs are and how they spread.

Answer 7

a sexually transmitted infection

spread by contact with sexual fluids/not using a condom during sexual intercourse

Question 8

During sexual intercourse a man places a condom over his penis.
Explain how this reduces his risk of being infected with an STI.

Answer 8

the condom is a barrier between the man’s skin and his partner’s sexual fluids, so pathogens that cause STIs cannot reach the man’s skin

Question 9

A newborn baby’s eyes are infected with Chlamydia.

Explain how this could happen.

Answer 9

During birth, the baby’s eyes and lungs may become contaminated with vaginal fluid containing the bacteria.