Biology

Molecular Genetics

851 Questions

Molecular genetics explores the mechanisms of genetic information transfer, including DNA replication, transcription, and translation. It is a core component of biology syllabi. These concepts frequently appear in general science sections of major competitive exams.

DNA replicationTranscription processTranslation processRNA typesCentral dogma

Molecular Genetics Questions

Multiple choice

Which among the following is a large class of self-catalytic ribozymes?

  1. Group I introns

  2. Group II introns

  3. Twintrons

  4. LtrA

  5. Spliceosome
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Group II introns is a large class of self-catalytic ribozymes as well as mobile genetic element found within the genes of all three domains of life. Ribozyme activity (e.g., Self-splicing) can occur under high-salt conditions in vitro.

Multiple choice

Which of the following snRNAs recognizes and binds to the sequence of the 5'-splice site of an intron in a strand of pre-mRNA?

  1. U1 spliceosomal RNA

  2. U2 spliceosomal RNA

  3. U4 spliceosomal RNA

  4. U5 spliceosomal RNA

  5. U6 spliceosomal RNA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

U1 spliceosomal RNA is the small nuclear RNA (snRNA) component of U1 snRNP (small nuclear ribonucleoprotein). Splicing or the removal of introns, is a major aspect of post-transcriptional modification. The U1 snRNP recognizes and binds to the sequence of the 5'-splice site of an intron in a strand of pre-mRNA.  

Multiple choice

Which among the following statements regarding the spliceosome is incorrect?

  1. Each spliceosome is composed of five small nuclear RNAs.

  2. The RNA component of the small nuclear ribonucleic protein or snRNP is rich in adenine.

  3. Introns typically have a GU nucleotide sequence at the 5' end splice site, and an AG at the 3' end splice site.

  4. A spliceosome is a large and complex molecular machine found primarily within the nucleus of eukaryotes.

  5. The spliceosome removes introns from a transcribed pre-mRNA.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The RNA component of the small nuclear ribonucleic protein or snRNP is rich in uridine (the nucleoside analog of the uracil nucleotide).

Multiple choice

Which among the following modes of alternative splicing is the rarest mode in mammals?

  1. Mutually exclusive exons

  2. Intron retention

  3. Alternative acceptor site

  4. Exon skipping or cassette exon

  5. Alternative donor site
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A sequence may be spliced out as an intron or simply retained. This is distinguished from exon skipping because the retained sequence is not flanked by introns. If the retained intron is in the coding region, the intron must encode amino acids in frame with the neighboring exons, or a stop codon or a shift in the reading frame will cause the protein to be non-functional. This is the rarest mode in mammals.

Multiple choice

Which of the following events does not occur in alternative splicing during gene expression?

  1. The exons to be retained in the mRNA are determined during the splicing process.

  2. U3 is not involved in mRNA splicing.

  3. Each intron has GU at its 3' end.

  4. Splicing is regulated by trans-acting proteins.

  5. Splicing silencers are sites to which splicing repressor proteins bind.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The typical eukaryotic nuclear intron has consensus sequences defining important regions. cc Near the 3' end there is a branch site.

Multiple choice

Which among the following statements regarding the synthesis of complementary DNA (cDNA) is incorrect?

  1. A eukaryotic cell transcribes the DNA into RNA.

  2. The mixture of mature mRNA strands is extracted from the cell.

  3. A poly-T oligonucleotide primer is hybridized onto the poly-A tail of the mature mRNA template.

  4. DNA polymerase is added, along with deoxynucleotide triphosphates (A, T, G, C).

  5. It is likely that the ssDNA forms a hairpin loop at the 3' end.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Reverse transcriptase is added, along with deoxynucleotide triphosphates (A, T, G, C). This synthesizes one complementary strand of DNA hybridized to the original mRNA strand.

Multiple choice

Assertion (A): Pre messenger RNA (pre-m-RNA) must be modified before translation. Reason (R): Pre-m-RNA contains the non-coding sequences (intron) within the coding region.

Directions: In the following question there are two statements, Assertion (A) and Reason (R). Consider both the statements independently and mark your answers as under:

1. If A and R both are correct and R is the correct explanation of A.
2. If A and R both are correct and R is not the correct explanation of A.
3. If A is correct and R is incorrect.
4. If A is incorrect and R is correct.
5. If A and R both are incorrect.

  1. 1

  2. 2

  3. 3

  4. 4

  5. 5
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Both Assertion (A) as well as Reason (R) are correct and R is the correct explanation of A. Pre messenger RNA (pre-m-RNA) must be modified before translation because pre-m-RNA contains the non-coding sequences (intron) within the coding region.

Multiple choice

Which of the following resembles the clover leaf?

  1. rRNA

  2. hnRNA

  3. tRNA

  4. mRNA

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The basic structure of tRNA assumes the pattern of clover leaf that carry amino acids to the ribosome for polymerisation into a polypeptide.

Multiple choice

The mutations forming nonsense codon in the transcribed mRNA is ________________.

  1. frameshift mutation

  2. nonsense mutation

  3. missense mutations

  4. neutral mutation

  5. silent mutations
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a nonsense codon in the transcribed mRNA, and possibly a truncated, and often nonfunctional protein product.