in class we have been learning about Francis crick and his p

in class we have been learning about Francis crick and his proflavin experiment. Point mutations. Nonsense, missense, deletions, general suppressors .

The sequence of a complete prokaryotic gene encoding a small protein6 amino acids long is shown below. All the written sequences on the template strand arc transcribed into RNA. A. Which is the template strand? Which direction (right to left, or left to right) docs RNA polymerase move along the template as it transcribes this gene? B. A mutation is found that no longer produces a protein 6 amino acids in length, but instead produces a protein 13 amino acids in length from this sequence. Identify the location of this mutation, and give an example of what change might produce this result (there is more than one possibility). C. This region of DNA is replicated starting from an origin of replication located to the left of this sequence, and proceeding through this sequence from left to right. When the replication fork passes through this region will the new strand of DNA that has the same sequence as the original top strand (as shown above) be produced by continuous or discontinuous replication?

Solution

A. In a DNA double helix the two strands are antiparallel that means they run in opposite directions to allow base pairing between them. This feature is essential for replication or transcription process.

B. Mutation in this case may be frameshift mutation which is also known as framing error mutation. This is caused by indels (insertions or deletions).

C. During transcription, the extension of RNA primers occurs by addition of nucleotides to the 3’ ends of both DNA strands so that growth occurs on both in 5’3’ direction only.