Biology

Molecular Genetics

917 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

Prions consist of

  1. DNA and RNA

  2. DNA, RNA and proteins

  3. RNA and proteins

  4. only proteins
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 A prion is an infectious agent, composed entirely of protein.

Multiple choice

Termination of amino acid chain requires codons

  1. UAG, UAA, UGA

  2. UUU, GGU, UGG

  3. GUG, UGG, AUG

  4. UGG, GGG, AUG
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

UAG, UAA, and UGA are the three stop/termination codons in the genetic code that signal the end of protein synthesis during translation. The other options contain codons that code for specific amino acids.

Multiple choice

Which one of the following is correct for virus?

  1. They have DNA or RNA

  2. They replicate inside the animal cell only

  3. They are living

  4. They are bigger than bacteria
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Viruses have either DNA or RNA as genetic material, never both. This is a fundamental viral characteristic. Option B is wrong because viruses replicate in various cells (plant, animal, bacterial), not just animal cells. Option C is wrong because viruses are not considered fully living (they need host cells). Option D is wrong because viruses are much smaller than bacteria.

Multiple choice

Which of the following is a soluble RNA?

  1. tRNA

  2. mRNA

  3. rRNA

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

tRNAs are short-chain RNA molecules present in the cell (in at least 20 varieties, each variety capable of combining with a specific amino acid) that attach the correct amino acid to the protein chain that is being synthesised at the ribosome of the cell (according to directions coded in the mRNA). It is also called soluble RNA because it is too small to be precipitated by ultracentrifugation at 100,000 g. It constitutes about 10-20% of the total RNA of the cell. Transfer RNA is a relatively small RNA having a molecular weight of about 25,000 to 30,000 and the sedimentation coefficient of mature eukaryote tRNA is 3.8S.

Multiple choice

Which of the following statements is not true for viroids?

  1. The viroid siRNAs contain sequences capable of complementary base pairing with the plant's messenger RNAs.

  2. Viroids are plant pathogens.

  3. Viroid genomes are extremely small in size.

  4. Viroid RNA codes for specific proteins.

  5. Some viroids are ribozymes.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Viroid RNA does not code for any protein. Their replication mechanism uses RNA polymerase II, a host cell enzyme normally associated with synthesis of messenger RNA from DNA, which instead catalyzes "rolling circle" synthesis of new RNA using the viroid's RNA as template.

Multiple choice

Which form(s) of chromatin is/are actively involved in transcription and protein synthesis?

  1. Euchromatin

  2. Heterochromatin

  3. Both (1) and (2)

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Euchromatin is a lightly packed form of chromatin (DNA, RNA and protein) that is enriched in genes and is often (but not always) under active transcription. Euchromatin comprises the most active portion of the genome within the cell nucleus. 92% of the human genome is euchromatic.

Multiple choice

The enzyme that catalyzes peptide bonding is located in the

  1. central part of transfer RNA

  2. smaller subunit of ribosome

  3. larger subunit of ribosome

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

The enzyme activity responsible for forming peptide bonds, known as peptidyl transferase, is a ribozyme located in the large subunit of the ribosome. It facilitates the link between the amino acid on the tRNA in the A-site and the growing polypeptide chain.

Multiple choice

Anticodons are found in

  1. DNA

  2. t RNA

  3. m RNA

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

Anticodons are sequences of three nucleotides in transfer RNA (tRNA) that are complementary to the codons found in messenger RNA (mRNA). They ensure that the correct amino acid is added to the polypeptide chain during translation.