NEET Biology: Molecular Biology questions with solutions

Q1. A novel species with double stranded genetic material consists of 5 bases namely P.Q. R. S. T. with percentages given below. Percentage 22 \( 28 \quad 22 \) Based on the above information, which ONE of the following infrences is NOT supported by the observation?

1. S- base pairs with T, and Q base pairs with R
2. S base pairs with \( Q \),and T base pairs with \( Q \)
3. P base pairs with \( R \), and \( S \) base pairs with \( Q \)
4. P base pairs with \( \mathrm{R} \), and T base pairs with \( \mathrm{Q} \)

Answer: S base pairs with \( Q \),and T base pairs with \( Q \)

In double-stranded genetic material, complementary bases must match in total abundance across the two strands. The only option that cannot be true is the one assigning the same base to pair with two different bases, which violates fixed pairing rules.

Q2. Choose the correct answer from the alternatives given : If the sequence of nitrogen bases of the coding strand of DNA in a transcription unit is: \( 5-A \) T \( G A A T G-3 \) the sequence of bases in its RNA transcript would be

1. 5-AUGAAUG-3
2. 5-UACUUAC-3
3. 5 сАUUсАU 3
4. 5-GUAAGUA-3.

Answer: 5-AUGAAUG-3

The coding strand has the same base sequence as the RNA transcript, except DNA uses thymine (T) while RNA uses uracil (U). So 5-ATGAATG-3 becomes 5-AUGAAUG-3.

Q3. The process of mRNA synthesis on a DNA is known as

1. Translation
2. Transcription
3. Transduction
4. Transformation

Answer: Transcription

mRNA is synthesized from a DNA template during transcription. Translation is the later step where ribosomes read mRNA to build protein, while transduction and transformation are forms of genetic transfer in bacteria.

Q4. The two polynucleotide chain in DNA are:

1. Semiconservative
2. Parallel
3. Discontinuous
4. Antiparallel

Answer: Antiparallel

DNA’s two polynucleotide strands are oriented in opposite directions, meaning one runs 5'→3' and the other 3'→5'. This opposite arrangement is called antiparallel.

Q5. Which enzyme plays important role in transcription?

1. DNA dependent RNA polymerase
2. DNA dependent DNA polymerase
3. RNA dependent DNA polymerase
4. RNA dependent RNA polyrnerase

Answer: DNA dependent RNA polymerase

Transcription is the process of making RNA from a DNA template, and the enzyme that catalyzes this is DNA-dependent RNA polymerase. DNA-dependent DNA polymerase is used in DNA replication, while RNA-dependent polymerases are involved in reverse transcription or RNA virus replication.

Q6. Which may be attached with adenine base in RNA?

1. Guanine
2. Cytosine
3. Uracil
4. Thymine

Answer: Uracil

In RNA, adenine pairs with uracil through two hydrogen bonds. Thymine is used in DNA, not RNA, so the correct attached base in RNA is uracil.