Chapter 5 — DNA and Genetic Information · 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.
A gene mutation occurs at the level of?
Correct answer: (B) The sequence of nitrogenous bases within the gene
Explanation: A gene mutation is a change in the sequence of nitrogenous bases within the gene itself.
The agents that cause mutations are called?
Correct answer: (B) Mutagens
Explanation: Mutagens are the agents that increase the rate at which mutations occur.
Are all mutations harmful?
Correct answer: (B) No, there are also beneficial or neutral mutations
Explanation: Mutations may be harmful, neutral (having no effect), or beneficial, and beneficial mutations are the basis of variation and evolution.
A substitution mutation means?
Correct answer: (A) Replacing one nitrogenous base with another in the DNA
Explanation: In substitution, one nitrogenous base is replaced by another, and this is a type of point mutation.
A missense mutation, in its effect?
Correct answer: (C) Changes a single amino acid in the protein
Explanation: In a missense mutation the codon changes into one coding for a different amino acid, so a single amino acid in the protein changes.
A mutation that occurs in the sex cells (gametes)?
Correct answer: (B) Is passed on to the following generations
Explanation: A mutation in the sex cells is inherited by the offspring, unlike a somatic mutation, which affects only the individual itself.
Inversion of a segment of a chromosome means?
Correct answer: (C) A segment detaches and returns to the same place in reversed order
Explanation: In inversion, a segment of the chromosome detaches and returns to its place but with a reversed gene order.
Down syndrome results from?
Correct answer: (D) An extra copy of chromosome 21 (trisomy)
Explanation: Down syndrome is a numerical chromosomal mutation: 3 copies of chromosome 21 instead of 2, making the total 47 chromosomes.
A point mutation changed a codon for an amino acid into a stop codon. The most likely result?
Correct answer: (D) Protein synthesis stops early, producing a short non-functional protein
Explanation: This is a nonsense mutation: an early stop codon halts translation, producing an incomplete, usually non-functional protein.
An insertion of 3 consecutive bases within a gene is most likely to?
Correct answer: (A) Add a single amino acid without shifting the reading frame
Explanation: Adding a number of bases that is a multiple of 3 adds or removes amino acids without shifting the reading frame, so the effect is less than a frameshift.
The first 10 questions in every subject are free, each with an explanation.