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AP Biology : 6.3 Transcription and RNA Processing – Exam Style questions with Answer- MCQ

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Question

A model that represents a process occurring in a cell of a particular organism is shown in Figure 1.

The figure presents a diagram of a segment of double stranded D N A helix where the two strands in the middle portion of the helix have separated from each other. Twelve bases are indicated on each of the two strands. Seven complementary bases, with the sequence A U G A U C U, are shown bound to the bottom of the two DNA strands, starting from the left end of the strand. An arrow above the seven bases points from left to right.

Figure 1. Process occurring in a cell

Which of the following correctly explains the process shown in Figure 1 ?

A. DNA replication is occurring because replication is semi-conservative and the new strand is a copy of the template strand.
B. Initiation of transcription is occurring because a strand of RNA is being produced from a DNA template strand.
C. Translation is occurring because the two strands have separated and a new strand is being produced.
D. Alternative splicing of mRNA is occurring because the mRNA strand is being synthesized from only one strand of DNA.

▶️Answer/Explanation

Ans: B
Transcription is occurring. Since uracil (U) is present in the new strand being formed, RNA is being formed from a DNA template.

Question

Figure 1 represents part of a process that occurs in eukaryotic cells. There are untranslated regions (UTR) in this sequence.

The figure presents a diagram representing a cellular process. At the top of the diagram is a line marked out into 7 segments. From left to right, the segments are labeled: 5 prime U T R, Exon 1, Intron 1, Exon 2, Intron 2, Exon 3, 3 prime U T R. Three arrows extend down from this top line. One arrow extends from Intron 1 in the top line to a line segment the size of intron 1 that is labeled as Intron 1. A second arrow extends from Intron 2 in the top line to a line segment the size of intron 2 that is labeled Intron 2. A third arrow extends from the top line to a line at the bottom of the diagram. The far left end of the bottom line has the label 5 prime cap followed by a small circle. Following this the line is then marked out into 6 segments that are labeled from left to right: 5 prime U T R, Exon 1, Exon 2, Exon 3, 3 prime U T R, Poly A Tail.

Figure 1. Cellular process involving nucleic acids

Which of the following best explains the process represented by Figure 1 ?

A. The synthesis of mRNA in the 5′ to 3′ direction from DNA
B. The modification of a protein to produce a functional form of that protein
C. The translation of an mRNA molecule into a polypeptide
D. The enzyme-regulated processing of pre‑mRNA into mature mRNA

▶️Answer/Explanation

Ans: D
The removal of introns and the addition of a 3′ poly‑A tail and a 5′GTP cap are associated with mRNA processing in eukaryotic cells, and the diagram reflects these changes.

Question

Figure 1 represents part of a process essential to gene expression.

The figure presents a diagram with a double helix of D N A. The two strands of the helix are paired at each end but are separated in the central portion. Bases of the nucleotides are indicated for the entire length of each strand. The left end of the upper strand is labeled 5 prime, and the right end is labeled 3 prime. The left end of the lower strand is labeled 3 prime, and the right end is labeled 5 prime. The lower strand is also labeled Strand X. An additional single strand of nucleotides that is complementary to the lower DNA strand is also present on the left and central portions of the figure. The sequence of the strand, from the left 5 prime end to the right 3 prime end, is as follows: A U G C C G C A A U C U G U U C A C G C A C U C A U G U G. Above the strand an arrow labeled Direction of Synthesis points along the strand from left to right.

Figure 1. Model of process involved in gene expression.

Which of the following best explains what strand X represents?

A. A complementary RNA sequence, because it contains thymine
B. The coding strand in this process, because it is being read 3′ to 5′
C. The antisense strand, because it is serving as a template
D. The pre‑mRNA, because it does not yet have a GTP cap

▶️Answer/Explanation

Ans: C
Strand X is serving as the template strand for the synthesis of a complementary strand of RNA. The template strand is also called the antisense strand.

Question

Which of the following correctly represents the mRNA sequence that
would be transcribed from the DNA sequence 3′ ACC GGT AAG TTC
5′?
(A) 3′ TGG CCA TTC AAG 5′
(B) 3′ UGG CCA UUC AAG 5′
(C) 5′ TGG CCA TTC AAG 3′
(D) 5′ UGG CCA UUC AAG 3′

▶️Answer/Explanation

Ans:

(D) The transcribed mRNA would be antiparallel to the given DNA
sequence, so it would start with the 5′ end. Also, in RNA, uracil
replaces thymine, and the other base-pairing rules are the same as those
found in DNA. Choices (A) and (B) are incorrect because the mRNA is
not antiparallel to the DNA sequence. Choices (A) and (C) are
incorrect because they contain thymine, which does not appear in
RNA.

Question

Which of the following processes is most similar in prokaryotes and
eukaryotes?
(A) alternative splicing of exons
(B) addition of a 3′ poly-A tail to mRNA
(C) addition of a 5′ GTP cap to mRNA
(D) transcription by RNA polymerase

▶️Answer/Explanation

Ans:

(D) Both prokaryotes and eukaryotes use RNA polymerase for
transcription. Only eukaryotes have alternative splicing of exons and
the addition of a 3′ poly-A tail and a 5′ GTP cap to mRNA, so choices
(A), (B), and (C) are incorrect.

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