Which of the statements about the production of a protein are correct?
- The sequence of bases in the gene determines the amino acid sequence used to make a protein.
- The mRNA molecules are made in the nucleus and they remain there.
- The ribosomes assemble amino acids together to make a protein.
A) 1 and 2 only
B) 1 and 3 only
C) 2 and 3 only
D) 2 only
▶️ Answer/Explanation
Ans: B
Statement 1 is correct: The DNA base sequence in a gene directly codes for the amino acid sequence of a protein through transcription and translation.
Statement 2 is incorrect: mRNA is synthesized in the nucleus but leaves to travel to ribosomes in the cytoplasm for translation.
Statement 3 is correct: Ribosomes are the cellular machinery that assemble amino acids into polypeptide chains during translation.
Since only statements 1 and 3 are correct, the answer is B (1 and 3 only).
The diagram shows the bases in a section of DNA from one strand only.
A−C−T−T−C−A−G−T−C
What is the base sequence on the complementary DNA strand?
A) G−C−T−T−C−G−A−T−C
B) G−T−C−C−T−G−A−C−T
C) T−C−A−A−C−T−G−A−C
D) T−G−A−A−G−T−C−A−G
▶️ Answer/Explanation
Ans: D
In DNA, base pairing follows specific rules: A (Adenine) pairs with T (Thymine), and C (Cytosine) pairs with G (Guanine). Given the strand A−C−T−T−C−A−G−T−C, the complementary strand is derived by pairing each base accordingly:
A → T, C → G, T → A, T → A, C → G, A → T, G → C, T → A, C → G
Thus, the complementary sequence is T−G−A−A−G−T−C−A−G, which matches option D.