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Subjects · Leaving Cert Biology

Leaving Cert Biology: DNA

How often DNA comes up on the Biology papers, every year it was asked, and questions to try.

HL Asked on 9 of the last 10 Higher Level papers, most recently in 2026. banker

OL Asked on 8 of the last 10 Ordinary Level papers, most recently in 2026. most years

June 2027 is the first exam on the new Biology course. These come from the 2016–2026 papers, so read them as a guide.

DNA, Higher Level(6 marks)

Quick ones on DNA.

(a)Base that pairs with guanine?
  1. Adenine
  2. Cytosine
  3. Thymine
(b)Base in RNA that replaces thymine?
  1. Cytosine
  2. Adenine
  3. Uracil
(c)Three bases on mRNA coding for one amino acid?
  1. Codon
  2. Allele
  3. Anticodon
Show the answers

(a) Cytosine

(b) Uracil

(c) Codon

Your turn: Higher Level questions on DNA.

Higher Level

Asked on 9 of the last 10 Higher Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q5, Q8, Q13
2025Q12
2024Q5, Q8
2023Q4
2022Q3, Q13
2021Q8
2019Q7, Q11
2018Q13
2017Q9, Q12
2016Not asked

Links open the State Examinations Commission’s paper for that year.

More DNA questions

DNA, 2 marks

The DNA backbone is alternating sugar and?

  1. Base
  2. Protein
  3. Phosphate
Show the answer

Phosphate

The sugar is deoxyribose. The bases point inward like the rungs of a ladder, twisted into a double helix.

DNA, 2 marks

Three bases on tRNA that pair with a codon?

  1. Gene
  2. Anticodon
  3. Stop codon
Show the answer

Anticodon

Complementary base pairing between anticodon and codon makes sure each tRNA brings the correct amino acid to the ribosome.

DNA, 2 marks

Anticodon that pairs with the codon AUG?

  1. UAC
  2. TAC
  3. AUG
Show the answer

UAC

A pairs with U, U with A and G with C, so AUG pairs with UAC. AUG is also the start codon.

Ordinary Level

Asked on 8 of the last 10 Ordinary Level papers, most recently in 2026. most years

Every paper, year by year

YearWhere it came up
2026Q12
2025Q12
2024Q13
2023Q6
2022Q5
2021Q12
2019Not asked
2018Q11
2017Not asked
2016Q9, Q10

Links open the State Examinations Commission’s paper for that year.

More DNA questions

DNA, 2 marks

What does DNA stand for?

  1. Diribonucleic acid
  2. Deoxyribonitric acid
  3. Deoxyribonucleic acid
Show the answer

Deoxyribonucleic acid

Learn the spelling: deoxyribonucleic acid. It carries the coded instructions for making the proteins of the cell.

DNA, 2 marks

What is the shape of a DNA molecule?

  1. A flat circle
  2. A double helix
  3. A single straight strand
Show the answer

A double helix

Two strands twisted around each other like a spiral ladder. Watson and Crick worked this shape out in 1953.

DNA, 2 marks

Where is most of a cell's DNA found?

  1. In the nucleus
  2. In the cytoplasm
  3. In the cell wall
Show the answer

In the nucleus

The nucleus protects the DNA. That is why the nucleus is called the control centre of the cell.

Other Biology topics

All of Leaving Cert Biology