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Ch. 8 - Molecular Biology of Transcription and RNA Processing
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 8 - Molecular Biology of Transcription and RNA ProcessingProblem 5b
Chapter 8, Problem 5b

The following is a portion of an mRNA sequence:
3'-AUCGUCAUGCAGA-5'
Write out the sequence and polarity of the DNA duplex that encodes this mRNA segment. Label the template and coding DNA strands.

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1
Identify the polarity of the given mRNA sequence. The sequence provided is 3'-AUCGUCAUGCAGA-5', which means it is written in the 3' to 5' direction. However, mRNA is conventionally written in the 5' to 3' direction, so reverse the sequence to 5'-AGACGUTGACGUA-3'.
Determine the complementary DNA strand (template strand) that would have been used to transcribe this mRNA. Remember that RNA pairs adenine (A) with uracil (U) and cytosine (C) with guanine (G). Replace U with T to reflect DNA pairing. The template strand will be complementary to the mRNA sequence.
Write the template DNA strand in the 3' to 5' direction, as DNA is antiparallel to the mRNA. For example, if the mRNA sequence is 5'-AGACGUTGACGUA-3', the template strand will be 3'-TCTGCACTGCAT-5'.
Determine the coding DNA strand, which is the strand complementary to the template strand. The coding strand will have the same sequence as the mRNA (except T replaces U) and will be written in the 5' to 3' direction.
Label the strands clearly: the template strand is the one used to transcribe the mRNA, and the coding strand is the one that matches the mRNA sequence (except for T replacing U).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Transcription

Transcription is the process by which the genetic information in DNA is copied into messenger RNA (mRNA). During this process, RNA polymerase synthesizes mRNA from a DNA template strand, following base-pairing rules where adenine (A) pairs with uracil (U) in RNA, and cytosine (C) pairs with guanine (G). Understanding transcription is essential for determining how mRNA sequences are derived from DNA.
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DNA Strands and Polarity

DNA consists of two strands that run in opposite directions, known as antiparallel strands. Each strand has a polarity, with one end designated as the 5' end and the other as the 3' end. The template strand is read in the 3' to 5' direction during transcription, while the coding strand, which has the same sequence as the mRNA (except for T instead of U), runs in the 5' to 3' direction. Recognizing the polarity is crucial for accurately writing the corresponding DNA sequence.
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Base Pairing Rules

Base pairing rules dictate how nucleotides pair in DNA and RNA. In DNA, adenine pairs with thymine (A-T) and cytosine pairs with guanine (C-G). In RNA, adenine pairs with uracil (A-U) instead of thymine. These rules are fundamental for determining the complementary DNA sequence that encodes a given mRNA sequence, ensuring accurate transcription and genetic fidelity.
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Related Practice
Textbook Question

The diagram below shows a DNA duplex. The template strand is identified, as is the location of the nucleotide. consensus sequences.

Assume this region contains a gene transcribed to form mRNA in a eukaryote. Identify the location of the most common promoter.

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Textbook Question

The diagram below shows a DNA duplex. The template strand is identified, as is the location of the nucleotide.

If this region is a eukaryotic gene transcribed by RNA polymerase III, where are the promoter consensus sequences located?

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Textbook Question

The following is a portion of an mRNA sequence:

3'-AUCGUCAUGCAGA-5'

During transcription, was the adenine at the left-hand side of the sequence the first or the last nucleotide used to build the portion of mRNA shown? Explain how you know.

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Textbook Question

The following is a portion of an mRNA sequence:

3'-AUCGUCAUGCAGA-5'

Identify the direction in which the promoter region for this gene will be located.

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Textbook Question

Compare and contrast the properties of DNA polymerase and RNA polymerase, listing at least three similarities and at least three differences between the molecules.

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Textbook Question

The DNA sequences shown below are from the promoter regions of six bacterial genes. In each case, the last nucleotide in the sequence (highlighted in blue) is the nucleotide that initiates transcription. Examine these sequences and identify the Pribnow box sequence at approximately -10 for each promoter.

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