A Level Biology Practice Exam

What characterizes the antisense strand during DNA transcription?

1. It runs from 5' to 3'

2. It is complementary to the sense strand and runs from 3' to 5'

3. It replicates independently of the sense strand

4. It has no role in protein synthesis

The correct answer is: It is complementary to the sense strand and runs from 3' to 5'

The antisense strand during DNA transcription is indeed characterized by being complementary to the sense strand and running from 3' to 5'. This strand serves as the template for the synthesis of messenger RNA (mRNA) during transcription. The mRNA is synthesized in the 5' to 3' direction, meaning that RNA polymerase reads the antisense strand from 3' to 5', which allows it to produce a complementary RNA sequence that matches the sense strand, aside from the substitution of uracil for thymine. This complementary nature is essential because it ensures that the genetic information is accurately transcribed for protein synthesis. Understanding this relationship between the strands is critical for grasping how genes are expressed in terms of transcription and subsequent translation into proteins. The correct identification of the antisense strand's function and structure is important in molecular biology and genetics.