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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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This sequence codes for 7 amino acids during protein synthesis T

Thymine can't be found in.................... mRNA

A cistron is..............the sequence of triplets on a section of DNA used to form a strand of

A Peptide Bond.............. links the amino acids in the primary structure of a protein


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Explain the function of the codons at each end of a strand of mRNA, during the process of
translation. (2)
*They function as start/stop/nonsense codons. The *start (codon) is needed to begin the
Polypeptide/protein synthesis and *the stop/nonsense (codon) is needed to end polypeptide

Suggest why a variety of…

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Explain why the processes shown in the flow diagram will only happen in response to some
types of bacteria. (3)
Because the protein nature of antigens/antibodies is different, the *antigens are specific to each
bacteria strain and the *antibodies need to be complementary/specific to the antigen so that
binding can…

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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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Suggest why health authorities in the USA are encouraging the reduction in the number of
prescriptions of antibiotics. (2)
Because *some bacteria can resist/are resistant to the antibiotics and this *resistance is
genetic/can be passed on. *MRSA, for example is already resistant to many antibiotics.

Explain why doctors have been…

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*A specific/humoral immune response to the synthetic antigen will be stimulated, i.e. *Effector B
cells will be produced by clonal expansion of B cells, involving cytokines or T helper cells will
activate B cells. These will then *produce B memory cells that will cause (2G12) antibodies to be
produced faster/in…

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Name two types of cell that HIV enters in the immune system.
*T helper/CD4 positive cell/lymphocytes; *phagocytic cells e.g. macrophages, dendritic cell

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…


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