Question

Below is a DNA sequence. Envision that this is a section of a DNA molecule that has separated in preparation for transcription, so you are only seeing the antisense strand. Construct the mRNA sequence transcribed from this template. Antisense DNA strand: 3 '-T A C T G A C T G A C G A T C-5'

Short answer

mRNA sequence: 5'-A U G A C U G A C U G C U A G-3'

Step-by-step solution

Understand Transcription Direction

Recognize that transcription proceeds in the 5' to 3' direction along the antisense DNA strand. This means that the RNA polymerase will use the antisense strand as a template, adding RNA nucleotides that are complementary to the DNA nucleotides on the antisense strand.

Identify Complementary Bases

Match each DNA base of the antisense strand with its complementary RNA base: adenine (A) pairs with uracil (U), thymine (T) pairs with adenine (A), cytosine (C) pairs with guanine (G), and guanine (G) pairs with cytosine (C).

Construct mRNA Sequence

Build the mRNA sequence by transcribing the complementary RNA bases from the 5' end to the 3' end of the DNA antisense strand. This means you'll start at the 'T' on the 3' end of the DNA antisense strand and move towards the 'C' on the 5' end.

Key concepts

Antisense DNA Strand

In the process of DNA transcription within microbiology, understanding the role of the antisense DNA strand is crucial. Often termed the template strand, this is the strand of DNA that serves as a guide for creating an mRNA sequence. The antisense DNA strand runs antiparallel to the coding strand, meaning if the coding strand goes in a 5' to 3' direction, the antisense strand will be oriented 3' to 5'.

During transcription, this strand's sequence of nucleotide bases is read by RNA polymerase, whereby the polymerase matches each DNA nucleotide with its RNA counterpart, but in the converse direction. For instance, if the antisense strand has a sequence of 3'-TACTGACTGACGATC-5', transcription proceeds in the opposite direction to synthesize a complementary mRNA strand. It is essential to visualize this antiparallel arrangement to comprehend the transcription dynamics fully.

mRNA Sequence

The mRNA sequence is the single-stranded copy of the genetic information dictated by the antisense DNA strand used during transcription. The primary function of the mRNA is to convey genetic instructions from DNA to the ribosome, where proteins are synthesized. The sequence of the mRNA is a chain of RNA nucleotides arranged in the 5' to 3' direction, mirroring the complementary bases of the antisense DNA strand but with one significant difference: in the RNA sequence, the base uracil (U) is used instead of thymine (T).

The constructed mRNA sequence corresponding to the given antisense DNA strand 3'-TACTGACTGACGATC-5' would therefore read 5'-AUGACUGACUGCUAG-3', which can be arrived at by transcribing complementary RNA bases from the 5' to the 3' end of the antisense DNA strand, as explained in the transcribing process.

Complementary RNA Bases

Understanding the concept of complementary RNA bases is key to grasping DNA transcription. Each DNA nucleotide base pairs with a specific RNA nucleotide during the process: adenine (A) with uracil (U), thymine (T) with adenine (A), cytosine (C) with guanine (G), and guanine (G) pairs with cytosine (C). This base-pairing rule is the core of the transcription process.

For example, in the given exercise, when faced with a thymine (T) in the antisense DNA strand, adenine (A) is the complementary RNA base during transcription. Therefore, the antisense DNA sequence 3'-TACTGACTGACGATC-5' will have complementary RNA bases that form the mRNA sequence starting with 'AUGACUGACUGCUAG'. These RNA bases are matched to the antisense DNA strand in a sequential fashion, adhering to the base-pairing principles and maintaining the necessary antiparallel orientation.