You have a segment of DNA that contains the following sequence: 5\'-GGACTAGACAAT

Question

You have a segment of DNA that contains the following sequence: 5'-GGACTAGACAATAGGGACCTAGAGATTCCGAAA-3' 3'-CCTGATCTGTTATCCCTGGATCTCTAAGGCTTT-5' You know that the RNA transcribed from this segment contains the following sequence: 5'-GGACUAGACAAUAGGGACCUAGAGAUUCCGAA-3' Which of the following choices best describes how transcription occurs? Select one: a. the top strand is the template strand; RNA polymerase moves along this strand from 5' to 3' b. the bottom strand is the template strand; RNA polymerase moves along this strand from 3' to 5' c. the top strand is the template strand; RNA polymerase moves along this strand from 3' to 5' d. the bottom strand is the template strand; RNA polymerase moves along this strand from 5' to 3'

Explanation / Answer

Ans. RNA polymerase binds to template DNA and carries out transcription in 5’-3’ direction.

So, RNA polymerase binds to template DNA strand (bottom strand) at its’ 3’end (left end of bottom strand) and carries out mRNA synthesis in 5’-3’ direction (complementary mRNA sequence from left to right of bottom strand).

Note that the top strand is coding strand whose sequence and polarity is exactly the same as that of mRNA except the T in coding strand is replaced by U in mRNA being synthesized.

Thus, correct option is- B. the bottom strand is the template strand; RNA polymerase moves along this strand from 3’-5’ (from 3’ end of template DNA towards 5’ end of template DNA). Therefore, the resultant mRNA is being synthesized complementary to template DNA and is being synthesized in 5’-3’ direction (i.e. 5’ end of mRNA is synthesized first, and 3’nd end is synthesized at the end of transcription).

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.