Viruses

Question 1

Genetic virus cycle

Answer 1

1. Attachment
   • virus recognises and connects to cell via receptor molecule on cell surface
   • specific protein in capsid connects to specific molecule on cell membrane
2. Entry• fuses with the membrane, tricks cell into being taken in via endocytosis or injects DNA into host cell
3. Replication and gene expression• viral genome copied and its genes are expressed to make viral proteins
4. Assembly• new viral particles are made from a copies of genome and viral proteins
5. Release
   • completed viral particles exot the cell and can infect other cells
   • exits via lysis cycle; exocytosis; bud off

Question 2

Compsition of virus

Answer 2

• DNA or RNA genome inside capsid
• Some external envelope
• Genes in a protein coat