Download Binary fission and viral reproduction

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.
http://www.sumanasinc.com/webcontent/animations/content/herpessimplex.
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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
One copy
of DNA is
made.
Plasmid
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 – 3.2.2 ‘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 10th December.