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mRNA Synthesis (Transcription) (Quiz 2)

How does transcription differ from DNA synthesis? The primary difference between transcription and DNA replication is that only a single strand of mRNA is produced during transcription. During DNA replication both strands need to be copied and DNA polymerase needs to work on both strands at the same time. Because DNA polymerase can only add new bases onto the free 3’ end of a molecule the two strands cannot be synthesized in the same way. The leading strand is synthesized as a continuous chain. The lagging strand is synthesized in pieces. In contrast, the single mRNA molecule is synthesized as a continuous strand. The other difference between the two processes is that during DNA synthesis the entire chromosome is copied. During transcription specific genes are transcribed in response to signals such as transcription factors.

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






1Synthesis of mRNA is
A)in the 5' to 3' direction with new nucleotides being added to the 5' end of the mRNA molecule.
B)in the 3' to 5' direction with new nucleotides being added to the 5' end of the mRNA molecule.
C)in the 5' to 3' direction with new nucleotides being added to the 3' end of the mRNA molecule.
D)in the 3' to 5' direction with new nucleotides being added to the 3' end of the mRNA molecule.
E)able to proceed either from the 5' to 3' or 3' to 5' direction.



2Sigma factor is
A)a subunit of mRNA
B)a subunit of RNA polymerase
C)a subunit of DNA
D)an enzyme needed for transcription to proceed
E)the place on RNA where RNA polymerase attaches



3Transcription begins when RNA polymerase binds to the
A)terminator on DNA
B)initiator on DNA
C)promoter on DNA
D)promoter on RNA



4When RNA polymerase reaches a specific sequence of nucleotides on the DNA called the transcription terminator, a hairpin loop structure forms on the DNA strand causing the RNA polymerase and mRNA to dissociate from the DNA.
A)True
B)False



5RNA polymerase copies the template strand of DNA making single-stranded mRNA complementary to the DNA template.
A)True
B)False







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