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Describe the structure of DNA - AQA - A-Level Biology - Question 10 - 2021 - Paper 1
Question 10
Describe the structure of DNA. - Polymer of nucleotides. - Each nucleotide formed from deoxyribose, a phosphate (group) and an organic/nitrogenous base. - Phosphodi... show full transcript
Worked Solution & Example Answer:Describe the structure of DNA - AQA - A-Level Biology - Question 10 - 2021 - Paper 1
Step 1
Structure of DNA
Answer
DNA, or deoxyribonucleic acid, is structured as a polymer made up of repeating units called nucleotides. Each nucleotide consists of three components:
- A 5-carbon sugar (deoxyribose): This sugar forms the backbone of DNA.
- A phosphate group: This group forms phosphodiester bonds with the sugar, linking the nucleotides together.
- A nitrogenous base: There are four types of bases—adenine (A), thymine (T), cytosine (C), and guanine (G)—that are crucial for genetic encoding.
The nucleotides are connected by phosphodiester bonds, which join the phosphate group of one nucleotide to the sugar of another.
DNA is typically described as a double helix, where two strands coil around each other. This helical structure is stabilized by hydrogen bonds that form specifically between the nitrogenous bases: adenine pairs with thymine (A-T) and cytosine pairs with guanine (C-G). This complementary base pairing is essential for DNA replication and function.