Chapter 6 — Nucleic Acids and Protein Synthesis · Biology. These are 10 questions from the Magmo3 bank on this lesson, from easy to hard. Solve each one, then open "Show answer and explanation". Magmo3 has 36 questions on this lesson, each with an explanation.
The process of translation takes place in?
Correct answer: (C) The ribosome
Explanation: Translation (the synthesis of protein from mRNA) takes place on the ribosome in the cytoplasm.
The pathway of transfer of genetic information (the central dogma) is?
Correct answer: (D) DNA → RNA → protein
Explanation: The central dogma: information passes from DNA by transcription to RNA, then by translation to protein.
The final product of the process of protein synthesis?
Correct answer: (C) A chain of amino acids (a protein)
Explanation: Protein synthesis produces a peptide chain of amino acids in an order determined by the codons.
The enzyme responsible for the process of transcription?
Correct answer: (B) RNA polymerase
Explanation: RNA polymerase builds the mRNA strand from the DNA template.
The type of bond that links the amino acids in the resulting protein?
Correct answer: (D) Peptide bond
Explanation: Amino acids are joined by peptide bonds to form the protein chain.
The start codon in protein synthesis is?
Correct answer: (B) AUG
Explanation: The start codon is AUG and it codes for the amino acid methionine; UAA, UAG, and UGA are stop codons.
The number of stop codons is?
Correct answer: (C) Three (UAA, UAG, and UGA)
Explanation: There are 3 stop codons that end translation: UAA, UAG, and UGA, and they do not code for amino acids.
The codon UUU codes for phenylalanine in bacteria and in humans alike, and phenylalanine is also coded by UUC. Which two properties of the genetic code do these facts show?
Correct answer: (A) It is universal and degenerate
Explanation: The same codon means the same amino acid in very different organisms, so the code is universal. One amino acid has more than one codon, so it is degenerate. Degenerate does not mean ambiguous: each codon still gives only one amino acid.
A protein is made of 150 amino acids. What is the minimum number of nucleotides in the coding region of its gene, counting both DNA strands and the stop codon?
Correct answer: (C) 906
Explanation: There are 150 codons plus 1 stop codon, so 151 × 3 = 453 nucleotides in the mRNA and in one DNA strand. Counting both strands gives 453 × 2 = 906.
An mRNA has the sequence 5'-CCAUGGCUAGAUGGUAAGC-3'. Translation starts at the first AUG from the 5' end and stops at the first stop codon (UAA, UAG or UGA) in the same reading frame. How many amino acids will the polypeptide contain?
Correct answer: (C) 4 amino acids
Explanation: Reading in triplets from the first AUG gives AUG GCU AGA UGG UAA: methionine and three more amino acids, then UAA, which codes for no amino acid, so the polypeptide has 4 amino acids. The UAG and the second AUG inside the sequence are not in this reading frame, so they are ignored.
The first 10 questions in every subject are free, each with an explanation.