IMO Practice Test — Molecular Basis of Inheritance
7 Questions • 15 min • Olympiad level
15:00
Question 1 of 7
If one DNA strand reads 5'-AATGC-3', the complementary strand reads:
TTACG
AATGC
GGCTA
UUACG
Explanation: Pairing A–T and G–C gives T-T-A-C-G as the complement.
Question 2 of 7
Complementary base pairing is the key to accurate replication because each old strand:
Specifies the exact sequence of its new partner
Is destroyed
Makes random bases
Becomes a protein
Explanation: Because A only pairs with T and G with C, each template dictates an exact complementary copy.
Question 3 of 7
A single base change in the DNA can alter one amino acid in a protein, as in sickle-cell anaemia. This shows that:
The base sequence of a gene determines the protein
Genes are made of protein
DNA does not affect proteins
Mutations never matter
Explanation: Changing the code changes the amino acid sequence, hence the protein — the basis of the disease.
Question 4 of 7
The genetic code is described as 'degenerate' because:
Most amino acids are coded by more than one codon
It does not work
Each codon codes many amino acids
There are only two codons
Explanation: Degeneracy means several different codons can specify the same amino acid.
Question 5 of 7
DNA fingerprinting can identify individuals because each person (except identical twins) has a:
Unique pattern in their DNA
Different number of cells
Different blood only
Identical genome
Explanation: Variations in DNA make each person's profile unique, useful in forensics and identification.
Question 6 of 7
The near-universality of the genetic code across bacteria, plants and humans is strong evidence that all life:
Shares a common origin
Evolved separately
Has no DNA
Uses different codes
Explanation: A shared code points to descent from a common ancestor.
Question 7 of 7
The lac operon staying OFF when no lactose is present benefits the cell by:
Saving energy by not making unneeded enzymes
Killing the cell
Making more DNA
Stopping all genes
Explanation: Producing lactose-digesting enzymes only when lactose is available avoids wasting resources.