A. Explain the reason why the cell requires a mechanism for identifying specific

Question

A. Explain the reason why the cell requires a mechanism for identifying specific sequences of DNA.

B. On average, how often would the nucleotide sequence CGATTG be expected to occur in a DNA strand 4000 bases long? Show your work and explain your answer.

C. Molecular processes depend upon sequence-specific interactions of proteins with DNA. Recognition sequences can be 4, 5, 6, 7, or even 8 base pairs in length for a single protein. What might be the advantages of a short recognition sequence? What might be the advantage of a longer recognition sequence?

Explanation / Answer

A)

DNA sequencing or identifying the specific sequences of DNA is the process of determining the precise order of nucleotides within a DNA molecule. The DNA comprises of 4 nucleotide bases namely: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). In a genome, these 4 bases are linked together in a specific order. Each ordered genome with a specific sequence of nucleotide bases codes for a certain protein (or enzyme (which is also a protein)). Thus, it is very important for a cell to have a mechanism to correctly identify the sequence of nucleotide bases in a genome because each sequence codes for a specific desired protein and any minor changes in the sequencing or interpretation of the sequence due to mutation will lead to abnormalities in the protein/enzyme synthesis and will lead to a disease state. Most cellular functions depends on the proteins which are synthesized post DNA sequencing, thus a mis-interpretation of the sequence or a false coding of the sequence will lead to abnormalities in the cellular function.

For example:

Consider that the nucleotide sequence of A-G-G-C-T-A-C-C-G-T-A codes for the production of the skin pigment Melanin. Now, if the cell mis-interprets the sequence and reads it as say, A-G-G-A-T-A-C-C-T-T-A. This may lead to absence of Melanin and may lead to Albimism.

Thank you!

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