Biology, Eighth Edition (Raven)

Chapter 15: Genes and How They Work


How is mRNA transcribed without disrupting a DNA molecule? Just like DNA synthesis, mRNA synthesis is done along small sections of DNA that are uncoiled and the two strands separated. Once the mRNA is created from one of the DNA strands, that portion of the DNA rejoins and recoils as more DNA opens up further down. In this way a continuous strand of mRNA can be synthesized without uncoiling a long sequence of DNA and separating the two strands. Only separating a small portion of the DNA at a time reduces the probability of damage to the molecule.

View the animation below, then complete the quiz to test your knowledge of the concept.


The Rho protein is involved in the _____ stage of transcription.
D)none of the above

Which of the following is correct regarding sigma factor?
A)it is involved in the termination of replication
B)it recognizes the promoter region
C)it forms an open complex
D)it forms mRNA
E)none of the above are correct

Which of the following occurs first in transcription?
A)action of the Rho protein
B)formation of a holoenzyme
C)formation of an open complex
D)formation of a closed complex
E)elongation of the mRNA

Unwinding of the DNA during transcription is the result of the activity of a helicase enzyme downstream of the RNA polymerase.

The RNA transcript being produced by the RNA polymerase is complementary to the template strand of the DNA.
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