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

The process of translation continues until...

  1. There are are amino acids added to the cytoplasm

  2. There are no more ribosomes

  3. A stop codon is reached

  4. The polypeptide chain has 30 amino acids
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Translation is terminated when the ribosome encounters a stop codon (UAA, UAG, or UGA) on the mRNA strand. Since there are no tRNAs with anticodons complementary to stop codons, release factors bind instead, causing the polypeptide chain to be released.

Multiple choice

Once a peptide bond is formed, what happens before the second last tRNA can detach?

  1. The ribosome moves along the mRNA by one codon

  2. Another tRNA attaches to the mRNA with its anticodon

  3. The ribosome detaches

  4. The polypeptide chain detaches
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

After a peptide bond is formed between the amino acids, translocation occurs, meaning the ribosome moves along the mRNA by one codon. This movement shifts the now-empty tRNA into the exit (E) site, allowing it to detach and leave the ribosome.

Multiple choice

Once there two tRNA molecules attach to the mRNA, what happens?

  1. The ribosome moves along the mRNA by one codon

  2. The first tRNA detaches

  3. The ribosome detaches

  4. A peptide bond is formed between the amino acids on the tRNA
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When two tRNA molecules are bound to adjacent codons on the mRNA within the ribosome, the amino acids they carry are positioned close together. An enzyme in the ribosome then catalyzes the formation of a peptide bond between these amino acids to grow the polypeptide chain.

Multiple choice

After the first tRNA anticodon attaches to the mRNA start codon, what happens next?

  1. The ribosome would move along the mRNA by one codon

  2. The amino acids join with a peptide bond

  3. The anticodon of another tRNA binds to the second mRNA codon

  4. The first tRNA detaches
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Once the initiator tRNA binds to the start codon, the next codon is exposed in the A site of the ribosome. The complementary anticodon of a second tRNA carrying its specific amino acid then binds to this second mRNA codon.

Multiple choice

Which of the following best describes the first step in translation?

  1. The amino acids join with a peptide bond

  2. The ribosome moves along the mRNA by one codon

  3. The anticodon of the first tRNA attaches to its mRNA codon

  4. A ribosome attaches to the mRNA
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Translation initiation begins when the small ribosomal subunit binds to the mRNA molecule, followed by the assembly of the complete ribosome. Only after this attachment can the initiator tRNA bind to the start codon.

Multiple choice

Which of the following is true in translation?

  1. Codons on mRNA match to identical anticodons on tRNA

  2. Anticodons on mRNA are complimentary to codons on tRNA

  3. Codons on mRNA are complimentary to anticodons on tRNA

  4. Anticodons on mRNA match to identical codons on tRNA
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

During translation, the three-nucleotide codons on the mRNA pair with complementary three-nucleotide anticodons on the tRNA molecules. This base-pairing ensures that the correct amino acid is added to the growing polypeptide chain.

Multiple choice

What best describes the role of tRNA?

  1. Carries an amino acid

  2. Carries a polypeptide chain

  3. Creates amino acids

  4. Creates peptide bonds
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Transfer RNA (tRNA) molecules function as adaptors that carry specific amino acids to the ribosome, matching them to the appropriate codons on the mRNA template. They do not synthesize amino acids or form peptide bonds themselves.

Multiple choice

During translation which of the following occurs?

  1. mRNA is used to form a polypeptide chain

  2. A polypeptide chain is used to form mRNA

  3. mRNA is created from DNA

  4. mRNA is used to create amino acids
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Translation is the process where the genetic code carried by mRNA is decoded to synthesize a specific polypeptide chain (protein). Transcription, not translation, is the process where mRNA is created from DNA.

Multiple choice

Virus contains

  1. DNA or RNA

  2. DNA

  3. RNA

  4. DNA and RNA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Viruses contain genetic material in the form of either DNA or RNA, but never both in the same virus particle.

Multiple choice

Gene expression refers to

  1. protein synthesis

  2. RNA synthesis

  3. both protein synthesis and RNA synthesis

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

Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product, which includes both RNA (transcription) and proteins (translation).

Multiple choice

The central dogma is

  1. RNA>DNA>Protein

  2. DNA>Protein>RNA

  3. Protein>DNA>RNA

  4. DNA>RNA>Protein
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The central dogma of molecular biology describes the flow of genetic information: DNA is transcribed into RNA, and RNA is translated into protein.