Describe the basic structure of a DNA and complementary base pairing.

DNA is a large polymer consisting of two DNA strands that form a double helix.  Each strand is made up of bases.  In DNA, there are four different bases:

Adenine, Thymine, Cytosine & Guanine

Pairs of bases form chemical cross-links between the two strands of DNA to form the final double helix.  The base pairs always form a particular way:

- Adenine always pairs with Thymine (A --- T)

- Cytosine always pairs with Guanine (C --- G)

This process is called complementary base pairing.

Lorna P. GCSE Biology tutor, A Level Biology tutor, GCSE Chemistry tu...

2 months ago

Answered by Lorna, a GCSE Biology tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist


£18 /hr

Joe R.

Degree: Biochemistry (Bachelors) - Exeter University

Subjects offered: Biology, Music+ 1 more

-Personal Statements-

“About Me: I'm currently studying Biochemistry at the University of Exeter. Along with my studies I also enjoy music - especially singing, being a choral scholar at the University Chapel Choir. Music is a large part of my life, especia...”

MyTutor guarantee

£18 /hr

Odette F.

Degree: Biological Sciences (Bachelors) - Exeter University

Subjects offered: Biology, Geography


“ABOUT ME: I am a 2nd Year Biology Student at the University of Exeter. Science as a whole, is a subject I am hugelyenthusiastic about and I would love to share this eagernesswith you! Having spent some of my Gap Year teaching abroad, I...”

£22 /hr

Jon S.

Degree: Economics & Bioscience (Bachelors) - Exeter University

Subjects offered: Biology, Maths+ 1 more


“I'm a first year student at Exeter University studying  Bioscience & Economics. I've enjoyed teaching for over a year now and I'm hoping my tutorials engage you with your subject, or at the very least help you get the grade you are lo...”

About the author

£18 /hr

Lorna P.

Degree: Veterinary Science (Bachelors) - Bristol University

Subjects offered: Biology, Maths+ 1 more


“Hello!  A bit about me.. I'm currently studying Veterinary Science at the University of Bristol, having previously completed a degree in Zoology at the University of Leeds. I'm a patient person and think teaching others is a very rew...”

MyTutor guarantee

You may also like...

Other GCSE Biology questions

What is the difference between an artery and a vein?

How do white blood cells protect the body?

What is the difference between a gene, a chromosome and DNA?

What are the effects of temperature on enzymes?

View GCSE Biology tutors


We use cookies to improve our service. By continuing to use this website, we'll assume that you're OK with this. Dismiss