How do bacteria reproduce? How are viruses replicated? Today we are covering from the specification:

How are viruses replicated? Remember that viruses are non-living. This means they are unable to reproduce. Viruses use the resources available in living cells to replicate their genetic material and produce new virus particles. html

Viruses Need living cells to act as a host Attach to the cell surface membrane Insert their genetic material into the cell

Viruses The cell copies the genetic material as part of its ‘normal’ processes. Each copy acts as the genetic code to produce a new capsid – the cells normal protein synthesis methods ensure this happens.

Viruses When the cell is filled with new viruses it bursts open (cell lysis) and the viruses are released to infect more cells.

How do bacteria reproduce? Asexually, via binary fission. This does not lead to an increase in variation. Asexual reproduction also means that the DNA is not altered (as it is via sexual reproduction). Offspring are genetically identical to each other and to the parent cell.

Bacterial DNA Plasmid One copy of DNA is made. Several copies of plasmids may be made. Daughter cells contain one copy of the circular DNA and a variable number of copies of the plasmids.

Binary fission Complete the worksheet, plotting your graph on graph paper. Can you suggest a reason why the number of cells levels off, then starts to decrease?

Homework You should now be able to complete the next section of the homework booklet – ‘All cells arise from other cells’. You should use your homework time this week to make a start on this section. I will be collecting your booklets in again on Thursday 10 th December.