Bacterial And Viral Replication

Question 1

Describe the process of viral replication

Answer 1

• viruses are acellular (non-living)
• so they require a host cell to replicate
• viruses contain a small genome in either RNA or DNA form
• virus contains specific proteins complementary to the specific receptors on the host cell
• virus ‘injects’ genome into cell or the virus enters the cell, therefore bringing the genome into the cell as well
• inside the cell viral genes are transcribed and this makes new proteins (for example capsid or receptor proteins. Reverse transcriptase for HIV)
• genetic material is replicated
• a new virus can now be assembled
• the new virus now leaves the host cell via the cell-surface membrane (for example budding) this can destroy the cell

Question 2

Describe the process of binary fission

Answer 2

• DNA replicated
• sell size increase
• chromosomes separated
• new cell wall and membrane formed in the middle
• divides into two daughter cells

Question 3

describe the features of a virus (6)

Answer 3

• RNA genomes/DNA
• complementary receptor proteins
• matrix
• protein shell (capsid)
• phospholipid envelope
• enzyme (reverse transcriptase)

Question 4

describe the role of reverse transcriptase

Answer 4

copies RNA and turns it into DNA
- uses RNA as a template and spare DNA nucleotides to form a DNA molecule

Question 5

which virus is enveloped and why

Answer 5

HIV
- takes part of the host cell with it when it leaves

Question 6

describe the complamentary receptor proteins

Answer 6

proteins called gp120 (glycoprotein 120)
- attaches to CD4 (cell surface proteins)