Molecular Genetics in Human Disease - Sickle Cell and Cancer

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Categories of genetic diseases? (5)
Dependant whether mutations are on: Autosome, X Chromosome or Mitachondrial Chromosome. And if Disease is: Recessive or Dominant
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Autosomal recessive diseases are characterized by? (1)
a particular pattern of inheritance. Disease is only expressed in mating between carriers.
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Example of an autosomal recessive disease? (1)
Sickle Cell Disease.
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What is sickle cell disease? (8)
Deformation of RBC caused by a missense mutation where adenin is replaced by thyamine causing an incorrect amino acid sequence in HbB subunit changing 6th codon from GAG to GTG (Glutamic Acid to Valine). This alters tertiary protein structure
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What is the mutant gene called? (1)
HbS
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What does this mutation result in? (4)
Change of structure from round to sickle shaped; especially in low O2 tension. Abnormal RBC are removed resulting in Sickle Cell Anaemia. Sickle RBC get stuck in capillaries depriving tissues of O2 leading to pain and organ failure.
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List the genes that may be implicated in cancer. (5)
Tumour suppressor genes. Oncogenes (inapp activated or over expressed). DNA repair genes. Telomerase. p53.
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3 types of oncogene. (3)
oncogene - inapp activated or over expressed. Proto-oncogene - A normal gene which, when altered by mutation, becomes an oncogene. Viral Oncogene - acquired cellular proto-oncogenes mutated to permanently active
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EGF. (5)
Usually activated by binding of EC ligand. In cancer gene can mutate to produce protein with permernantley active tyrosine kinase region; leading to tumour development. EGF such as HER2 - breast cancer. Treated with HERCEPTIN
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Function of p53 (6)
Normally functions to inhibit cell proliferation. p53 regulates progression through the ceel cycle, especially at G1-S checkpoint. It prevents damaged DNA entering the S phase; allowing time for repair. If repair fails it induces apoptosis.
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Result of p53 mutations. (6)
Loss-of-function mutations promote cancer. Mutation is recessive, mainly caused by a missense mutation changing single AA, or simple deletions. Heritable mutations pose high cancer risk. p53 mutations present in 50% of cancers.
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p53 flowchart. (4)
DNA damage -> p53 -> Repression of BCL2 transcription. Inc of BAX gene transcription. -> Dec BCL2. Inc BAX -> Apoptosis
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Card 2

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Autosomal recessive diseases are characterized by? (1)

Back

a particular pattern of inheritance. Disease is only expressed in mating between carriers.

Card 3

Front

Example of an autosomal recessive disease? (1)

Back

Preview of the front of card 3

Card 4

Front

What is sickle cell disease? (8)

Back

Preview of the front of card 4

Card 5

Front

What is the mutant gene called? (1)

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