Free Biochemistry Genetic and Molecular Biology Questions and Answers — Questions and Answers
Question 1: Which of the following is true about the DNA replication?
- It occurs only during mitosis.
- It is conservative, where both parent strands remain together.
- It is semiconservative, where each daughter DNA molecule has one parent and one new strand. (Correct answer)
- It does not require a primer to start synthesis.
Correct answer: It is semiconservative, where each daughter DNA molecule has one parent and one new strand.
DNA replication is a semiconservative process, meaning that each new double helix consists of one original (parental) strand and one newly synthesized strand. This mechanism ensures that genetic information is accurately copied and passed on to daughter cells. The parental strand serves as a template for the synthesis of the new complementary strand.
Question 2: Which enzyme is responsible for unwinding the DNA double helix replication?
- DNA polymerase
- Helicase (Correct answer)
- Ligase
- Topoisomerase
Correct answer: Helicase
Helicase is the enzyme responsible for unwinding the DNA double helix during replication. It breaks the hydrogen bonds between complementary base pairs, separating the two strands to create a replication fork. This unwinding is essential to expose the single-stranded DNA templates, allowing DNA polymerase to synthesize new DNA strands.
Question 3: In transcription, which of the following statements is correct?
- Both DNA strands are transcribed into RNA.
- Transcription occurs in the cytoplasm of eukaryotic cells.
- RNA polymerase synthesizes RNA in the 5' to 3' direction. (Correct answer)
- The newly synthesized RNA remains permanently bound to the DNA template.
Correct answer: RNA polymerase synthesizes RNA in the 5' to 3' direction.
During transcription, RNA polymerase synthesizes RNA in the 5' to 3' direction, reading the DNA template strand in the 3' to 5' direction. This directional synthesis is a fundamental characteristic of nucleic acid polymerization. Only one DNA strand serves as the template for RNA synthesis, and in eukaryotes, this process occurs in the nucleus.
Question 4: Which of the following is NOT involved in post-transcriptional modification of eukaryotic mRNA?
- 5' capping
- Splicing out introns
- Polyadenylation at the 3' end
- Addition of a primer (Correct answer)
Correct answer: Addition of a primer
Post-transcriptional modification of eukaryotic mRNA involves several crucial steps, including the addition of a 5' cap, splicing out introns, and polyadenylation at the 3' end. These modifications protect the mRNA, facilitate its export from the nucleus, and enhance its translation efficiency. The addition of a primer is a step in DNA replication, not mRNA processing.
Question 5: Which of the following best describes the function of tRNA in translation?
- Catalyzes peptide bond formation between amino acids.
- Carries amino acids to the ribosome and matches them to the mRNA codon. (Correct answer)
- Acts as the template for protein synthesis.
- Transports mRNA from the nucleus to the cytoplasm.
Correct answer: Carries amino acids to the ribosome and matches them to the mRNA codon.
Transfer RNA (tRNA) plays a crucial role in translation by acting as an adaptor molecule. Each tRNA carries a specific amino acid and has an anticodon that base-pairs with a complementary codon on the mRNA molecule. This ensures that the correct amino acid is delivered to the ribosome and incorporated into the growing polypeptide chain according to the mRNA sequence.
Free Biochemistry Genetic and Molecular Biology Questions and Answers
Which of the following is true about the DNA replication?