1.Sickle cell disease is caused by an apparently minor change in the sequence of
ID: 11832 • Letter: 1
Question
1.Sickle cell disease is caused by an apparently minor change in the sequence of bases in the DNA which codes for the beta chain in hemoglobin. The sequence for the start (the first eight amino acids in a sequence of 146) of the normal hemoglobin B chain is:
valine-histidine-leucine-threonine-proline-glutamate-lysine...
whereas that for abnormal hemoglobin B (which leads to sickle cell disease) is:
valine-histidine-leucine-threonine-proline-valine-glutamate-lysine...
What is the minimum change necessary in the mRNA code for this sequence to bring about this change—from glutamate to valine? Indicate the original and mutated codon.
2.Explain this statement: "The secret of protein synthesis lies in nucleotide complementarity."
Explanation / Answer
In order to answer this, you must refer to a genetic code chart showing which codons "call" for which amino acids. Often a change (mutation) in only one nitrogenous base (for example Thymine instead of Cytosine) will code for a totally different amino acid.
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