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 bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Choose the correct answer from the alternatives given :
In some viruses, DNA is synthesised by using RNA as template. Such a DNA is called

  1. A-DNA

  2. B-DNA

  3. cDNA

  4. rDNA
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Complimentary DNA( cDNA) is DNA synthesized from a single-stranded RNA template in a reaction catalyzed by the enzyme reverse transcriptase. RNA of viruses first synthesizes complementary DNA (cDNA) through reverse transcription. DNA then transfers information to RNA which takes part in the translation of coded information to form a polypeptide. 

So, the correct answer is 'cDNA'.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

What is a codon?

  1. A group of three nucleotide sequences.

  2. The nucleotide units between the start and stop codes.

  3. The nucleotide sequence that serves as the instructions for a protein.

  4. A single nucleotide in an mRNA sequence.

  5. The sequence of nucleotide that signals the start or shop of protein synthesis.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A codon is defined as a sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule. These codon translates to form protein sequences.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Teminism refers to

  1. Protein synthesis

  2. Transcription

  3. Reverse Transcription

  4. Restriction digestion
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Teminism is basically a theory. It is also known as reverse transcription. It was discovered by Temin and Baltimore in 1978. In molecular biology, it explains RNA can act as template strand for DNA formation. So, it means that DNA can be synthesized from RNA.

So, the correct answer is ' Reverse transcription'. 

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

The process of formation of DNA from RNA is known as

  1. Reverse transcription

  2. Translation

  3. Thigmotropism

  4. Teminism
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The process of formation of DNA from RNA is called reverse transcription and is observed when a virus with RNA as genetic material infects a host, containing DNA as genetic material
Example, HIV infection in humans
Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Genetic information are transferred from nucleus to cytoplasm of cell through

  1. DNA

  2. RNA

  3. Lysosomes

  4. ACTH
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Genetic information are transferred from nucleus to cytoplasm of cell through RNA. In eukaryotic cells, once precursor mRNA (pre-mRNA) has been transcribed from DNA, it is processed to mature mRNA. This removes its introns, non-coding sections, of the pre-mRNA. The mRNA is then exported from the nucleus to the cytoplasm, where it is bound to ribosomes and translated into its corresponding protein form with the help of tRNA. Ribonucleic acid (RNA) is a polymeric molecule. It is implicated in a varied sort of biological roles in coding, decoding, regulation, and expression of genes.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

The information carried by RNA in retroviruses is put in the DNA code by

  1. DNA polymerase

  2. DNA ligase

  3. RNA synthetase

  4. Reverse transcriptase
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

  • Reverse transcriptase enzyme is an enzyme that is used to generate cDNA from RNA template through the reverse transcription process. This is seen in many retroviruses to replicate their genomes.
  • DNA polymerase enzyme helps in DNA synthesis using DNA template, a process called replication.
  • DNA ligase is used to join DNA fragments during DNA repair or its replication.
So, the correct option is 'Reverse transcriptase'.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Reverse transcriptase is

  1. RNA dependent RNA polymerase

  2. DNA dependent RNA polymerase

  3. DNA dependent DNA polymerase

  4. RNA dependent DNA polymerase
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Reverse transcriptase is an RNA dependent DNA polymerase enzyme which means it uses RNA primers to synthesize DNA molecules. Reverse transcriptase enzyme used to generate complementary DNA (cDNA) from an RNA template by the process called reverse transcription. Retroviruses contain reverse transcriptase enzyme which converts their RNA genome into cDNA that can be incorporated into the host genome. 

So, the correct answer is 'RNA dependent DNA polymerase'.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

A codon is read in

  1. 3 5 direction

  2. 5 3' direction

  3. 3 6' direction

  4. 6' 3' direction
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Codons are read in the 5' to 3' direction on the mRNA molecule during translation. This is the same direction as RNA synthesis during transcription. The ribosome moves along the mRNA from 5' end toward 3' end, reading each codon sequentially. Options A and C have incorrect notation (3' 5', 3' 6'). Option D has non-standard notation (6'). Option B is correct.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Khorana et al synthesised RNA with copolymer of UGUGUGUGUG... It produced a peptide with alternate cysteine and valine. The codons for the two are

  1. UGU and GUG

  2. UUG and GGU

  3. GUG and UGU

  4. UGG and GUU
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A repeating UGUGUG... sequence produces codons UGU and GUG. UGU codes for cysteine and GUG codes for valine, matching the observed peptide.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Central dogma of protein synthesis consists of

  1. $DNA \overset{translation}{\rightarrow} mRNA \overset{transcriptionlation}{\rightarrow} Protein$
  2. $DNA \overset{transcription}{\rightarrow} mRNA \overset{translation}{\rightarrow} Protein$
  3. $RNA \overset{replication}{\rightarrow} DNA \overset{translation}{\rightarrow} Protein$
  4. $RNA \overset{transcriptions}{\rightarrow} mRNA \overset{translation}{\rightarrow} Protein$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The central dogma states that genetic information flows from DNA to RNA via transcription, and from RNA to protein via translation.