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RNA Structure and Functions (Medical Entrance)

Description: proteins
Number of Questions: 30
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Tags: proteins Nucleic Acids
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Which of the following is/are the site of mRNA synthesis?

  1. Cytoplasm

  2. Nucleus

  3. Ribosomes

  4. Mitochondria


Correct Option: B
Explanation:

The site of mRNA synthesis is nucleus. It is synthesised from DNA template in a process called transcription.

Which of the following bases is absent from RNA?

  1. Adenine

  2. Uracil

  3. Thymine

  4. Cytosine


Correct Option: C
Explanation:

Thymine is absent from RNA. It gets replaced by Uracil in RNA.

Which of the following RNAs ferries amino acids to ribosomes for protein synthesis?

  1. rRNA

  2. mRNA

  3. tRNA

  4. SnRNA


Correct Option: C
Explanation:

tRNA ferries amino acids to ribosomes for protein synthesis. As it functions in transfer of amino acids, it is therefore called transfer RNA.

RNA does not follow Chargaff's rules because it

  1. has pyrimidines different from DNA

  2. has sugar different from DNA

  3. is a single stranded molecule

  4. is a labile molecule


Correct Option: C
Explanation:

Being a single stranded structure, it does not follow Chargaff's rules. Double strand is necessary for base pairing, whose rules were formulated by Chargaff.

The site for translation of proteins is synthesised by

  1. mRNA

  2. tRNA

  3. rRNA

  4. hnRNA


Correct Option: C
Explanation:

The site for synthesis of proteins, i.e. ribosomes is synthesised by rRNA.

Which of the following pairs is incorrect?

  1. mRNA - nucleus

  2. tRNA - thymine

  3. dsRNA - hepatitis C virus

  4. Reverse transcriptase - retrovirus


Correct Option: C
Explanation:

Hepatitis C is a single stranded RNA virus.

Which of the following types of RNA is easily soluble in cytoplasm?

  1. rRNA

  2. mRNA

  3. tRNA

  4. hnRNA


Correct Option: C
Explanation:

tRNA is a very small molecule and thus, easily solubilises in cytoplasm.

Which of the following functional concepts links DNA and RNA together?

  1. One gene one poly-peptide concept

  2. Central dogma

  3. Codon degeneracy

  4. Coupling and repulsion hypothesis


Correct Option: B
Explanation:

The central dogma of molecular biology explains that DNA codes for RNA, which codes for proteins. Thus, DNA and RNA are functionally linked together by central dogma.

7-Methyl guanosine triphosphate caps the 5' terminal end of

  1. tRNA

  2. mRNA

  3. rRNA

  4. hnRNA


Correct Option: B
Explanation:

7-Methyl guanosine triphosphate caps the 5' terminal end of mRNA. This cap is involved in recognition of mRNA by translating machinery.

mRNA is protected from specific exonucleases due to

  1. 5' cap

  2. 3' tail

  3. Both (1) and (2)

  4. coding sequence


Correct Option: C
Explanation:

Both 5' cap and 3' tail impart stability to mRNA by protecting it from specific exonucleases.

The 3' end of most mRNA's have

  1. poly G tail

  2. poly A tail

  3. poly C tail

  4. poly U tail


Correct Option: B
Explanation:

The 3' end of most mRNA's has a poly A tail. It prevents the attack by 3' exonucleases.

What percentage of heterogeneous nuclear RNA is processed to mature mRNA?

  1. 75%

  2. 25%

  3. 100%

  4. 50%


Correct Option: B
Explanation:

25% of hnRNA is processed to mature mRNA.

Which of the following is the immediate precursor of mRNA?

  1. A single strand of DNA

  2. Heterogeneous nuclear RNA

  3. rRNA

  4. Small interfering RNA


Correct Option: B
Explanation:

Heterogeneous nuclear RNA acts as immediate precursor for synthesis of mRNA. Mature mRNA is formed from hnRNA by capping, tailing, splicing and base modification.

Which of the following acts as an adapter for the translation of the sequence of nucleotides of mRNA into specific amino acids?

  1. rRNA

  2. tRNA

  3. Ribosomes

  4. miRNA


Correct Option: B
Explanation:

tRNA acts as an adapter for the translation of the sequence of nucleotides of the mRNA into specific amino acids.

Which of the following is a clover leaf-like structure?

  1. Primary structure of tRNA

  2. Secondary structure of tRNA

  3. Tertiary structure of tRNA

  4. Denatured tRNA


Correct Option: B
Explanation:

Each single tRNA shows extensive internal base pairing and acquires a clover leaf-like structure. The structure is stabilised by hydrogen bonding between the bases and is a consistent feature.

Which arm of tRNA binds to amino acids?

  1. Acceptor arm

  2. Anti-codon arm

  3. DHU arm

  4. ΤψC arm


Correct Option: A
Explanation:

Amino acids bind to acceptor arm of tRNA.

The 3' end of the acceptor arm of tRNA has

  1. TTA

  2. GGA

  3. CCA

  4. UUA


Correct Option: C
Explanation:

The 3' end of the acceptor arm of tRNA has the sequence CCA. This attachment is done post-transcriptionally.

U1, U2, U4, U5 and U6 are the types of

  1. heterogeneous nuclear RNA

  2. micro RNA

  3. small nuclear RNA

  4. small interfering RNA


Correct Option: C
Explanation:

U1, U2, U4, U5 and U6 are the types of small nuclear RNA. They constitute protein-RNA complex functioning as spliceosome.

Which of the following RNAs is used to knock down specific protein levels in the laboratory?

  1. miRNA

  2. siRNA

  3. snRNA

  4. hnRNA


Correct Option: B
Explanation:

siRNA is frequently used to decrease or knock down specific protein levels in lab experiments. siRNA forms perfect RNA-RNA hybrids with mRNA and decreases protein synthesis.

Which of the following processes transfers the information from DNA to RNA?

  1. Translation

  2. Transcription

  3. Replication

  4. Transduction


Correct Option: B
Explanation:

Transcription is the process of transferring information from DNA to RNA.

Small nuclear RNA is involved in

  1. arresting translation

  2. mRNA processing and gene regulation

  3. inhibition of gene expression

  4. formation of mRNA


Correct Option: B
Explanation:

Small nuclear RNA are involved in mRNA processing and gene regulation.

Which of the following RNAs is the smallest?

  1. rRNA

  2. tRNA

  3. mRNA

  4. hnRNA


Correct Option: B
Explanation:

The smallest RNA is tRNA with molecular weight approximately equal to 10^4. Due to small size, they are easily soluble in cytoplasm.

Which of the following is/are a ribozyme?

  1. Helicase

  2. tRNA

  3. rRNA

  4. Both (2) and (3)


Correct Option: C
Explanation:

rRNA is a ribozyme because it performs peptidyl transferase activity.

The 40S subunit of rRNA consists of

  1. 18S RNA

  2. 5.8S RNA

  3. 28S RNA

  4. 5S RNA


Correct Option: A
Explanation:

40S subunit contains only a single 18S RNA.

Which of the following arms of tRNA differentiates it into class I and class II tRNA?

  1. DHU arm

  2. Extra arm

  3. TΨC arm

  4. Anti-codon arm


Correct Option: B
Explanation:

The length of extra arm differentiates tRNA into class I and class II types. Class I tRNA has a shorter extra arm, i.e. 3-5 base pairs long. Class II tRNA has a longer extra arm, i.e. 13-21 base pairs long.

The sequence of three consecutive bases in tRNA molecule, which specifically binds to a complementary code sequence in mRNA, is known as

  1. triplet codon

  2. anti-codon

  3. nonsense codon

  4. termination codon


Correct Option: B
Explanation:

Anti-codon refers to the sequence of three consecutive bases in tRNA molecule, which specifically binds to a complementary code sequence in mRNA.

TΨC arm consists of

  1. all adenine

  2. all uridine

  3. pseudouridine

  4. pseudothymine


Correct Option: C
Explanation:

TΨC arm is made up of pseudouridine and that is why, it is named TΨC arm. Ψ stands for pseudouridine.

The base sequence of anti-codon arm should be complimentary to

  1. base sequence of rRNA

  2. base sequence of mRNA

  3. sequence of acceptor arm

  4. sequence of DHU arm


Correct Option: B
Explanation:

The base sequence of anti-codon arm should be complimentary to mRNA, which is mandatory for translation.

What is the function of aminoacyl tRNA synthetase?

  1. Synthesising amino acids

  2. Adding amino acids to the acceptor arm

  3. Transferring amino acids to mRNA

  4. Synthesis of proteins


Correct Option: B
Explanation:

Aminoacyl tRNA synthetase adds amino acids to the acceptor arm.

Match the following:

Column I
Column II
1. Acceptor arm a. 5bp
2. Anti-codon arm b. 3-4 bp
3. DHU arm c. 13-21 bp
4. Class 2 tRNA extra arm d. 7 bp
  1. 1 - a, 2 - b, 3 - c, 4 - d

  2. 1 - d, 2 - a, 3 - b, 4 - c

  3. 1 - d, 2 - c, 3 - b, 4 - a

  4. 1 - c, 2 - d, 3 - b, 4 - a


Correct Option: B
Explanation:

This is the correct matching as acceptor arm is 7 bp long, anti-codon arm is 5 bp long, DHU arm is 3-4 bp long and class II RNA extra arm is 13-21 bp long.

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