OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

Disable ads (and more) with a membership for a one time $2.99 payment

Master GCSE Biology with our interactive exam quizzes. Utilize dynamic questions and thorough explanations to boost your understanding and excel in your GCSE Biology exam!

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

Practice this question and more.

Which of the following pairs are complementary base pairs in DNA?

Adenine and Cytosine
Thymine and Guanine
Adenine and Thymine
Cytosine and Uracil

The correct answer is: Adenine and Thymine

Adenine and Thymine are known as complementary base pairs in DNA, meaning they form specific hydrogen bonds with each other. In the structure of DNA, adenine (A) pairs with thymine (T) through two hydrogen bonds, which helps maintain the double helix shape of the DNA molecule. This pairing is crucial for accurate DNA replication and transcription processes. Other base pairs that are complementary in DNA include Cytosine and Guanine, but in the options provided, only adenine and thymine specifically fit the criteria of complementary base pairs. The relationships among the bases ensure the genetic information can be reliably copied and expressed.