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Topic 6: Immunity, Infections and Forensics
DNA Profiling
Polymerase is the.... enzyme used in the Polymerase Chain Reaction to amplify DNA in a small
sample of blood taken from a crime scene.

Gel Electrophoresis is the .....process used to separate DNA fragments to create a DNA profile

Describe how gel…

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Explain how the results of DNA profiling of tissue samples from the two sub-species could be
used to provide evidence that they share common ancestry. (3)
DNA profiling will *produce bands that will have spread to *certain positions. *Common/similar bands
will contain similar DNA fragments; *the more similar these patterns,…

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Describe the role of microorganisms in the recycling of the carbon from compounds in a dead
animal. (3)
Decomposition/putrefaction occurs by microorganisms, they may digest the carbon in the animal and
then release the carbon into the atmosphere by *respiration where the *carbon dioxide is used for
photosynthesis. *Methane is…

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The polypeptide chain would be synthesised on the *ribosomes attached to the membrane of the
rough endoplasmic reticulum. *The ribosomes consist of rRNA and are a protein component of two
sub-units/ a large and small sub-unit.


Explain why a molecule of DNA can be described as a double-stranded polynucleotide. (3)…

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helicase and mRNA is synthesised).*Post-transcriptional modification of mRNA then occurs where
introns (non-coding regions of DNA) are removed by splicing using the enzyme spliceosome, leaving
only exons behind in the mRNA to join back together. After modification the *mRNA moves from
nucleus to the cytoplasm through a pore in the…

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When MRSA enters the blood it can stimulate the production of several different clones of
plasma cells. These produce a variety of antibodies (polyclonal antibodies). Suggest an
explanation for this. (4)
Because the *bacterium is made of many different polymers/chemicals *which can act as different
antigens, *individual B-lymphocytes will recognise…

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*An antibiotic is used to control/kill/prevent reproduction of bacteria. *Bacteriostatic antibiotics will
prevent the reproduction/division/multiplication/growth of bacteria whereas *bactericidal
antibiotics will destroy/kill the bacteria.

Suggest why antibiotics may be used as part of the treatment for influenza. (2)
Because *influenza may allow the development of other diseases e.g. opportunistic infections…

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*A placebo has no effect on the bacteria *so there will be more bacteria, and *thus more
lymphocytes due to *clonal expansion.




Vaccinations and prevention.
Suggest how
scientists may be able to develop a means of producing active immunity to HIV infection using
synthetic HIV antigens. (5)
*This will be…

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State how the genetic material in HIV differs from the genetic material in the Mycobacterium
tuberculosis that causes TB. (2)
*RNA is found in HIV/ virus and DNA in the bacterium/TB, *the nucleic acid in the bacterium is circular
whereas it is linear in HIV. *There are also plasmids in…

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Because *HIV has many varieties of strains/antigens/protein coats, *some of these strains are/will
become resistant to a specific/particular drug and so *would survive if only one/the same drug was
used. *A mixture of drugs has more chance of getting rid of all/ more strains.
*A concoction of drugs are used…

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