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DNA Structure
Jamie Z 2024-10-22Learning Goals
- Describe the structure of a DNA molecule. (Double Helix)
- Identify the following parts of a DNA molecule: sugar (deoxyribose), phosphate, nitrogen base, nucleotide, sugar-phosphate backbone, hydrogen bonds.
- Explain the complementary nature of base pairing in DNA
- Determine a complementary base sequence for a given DNA strand.
What is DNA?
- All living things have DNA and are unique
- DNA molecules carry the code that controls what your cells are made of and what they do
1. Double Helix
- DNA is arranged in a double helix: Two strands of DNA are twisted together resembling a long . spiralling string
- Made up of a sugar phosphate backbone and nitrogen bases
2. Sugar Phosphate Backbone
- DNA contains two long spiralling strands called sugar phosphate backbones
- They resemble the side rails of a ladder
- The sugar phosphate backbone is made up of two repeating units: Deoxyribose sugar and phosphate groups
- They are bonded with covalent bonds
3. Nitrogen Bases
- The nitrogenous bases are bound to the deoxyribose sugar**.**
- The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the rungs of the ladder .
- Sequences of bases within a strand of DNA carry instructions for the cell to make proteins.
There are 4 types of bases
- Adenine (A)
- Thymine (T)
- Guanine (G)
- Cytosine (C)
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- The two nitrogenous bases in a complementary pair are held together by hydrogen bonds
4. DNA Nucleotide
- A molecule of DNA is made up of millions of subunits called Nucleotides
- One phosphate, one deoxyribose sugar and one nitrogen base make up a nucleotide
- DNA is made up of repeating nucleotides, this makes up one nucleotide the basic building block of DNA
- The sugar and phosphate are always the same, so nucleotides only differ in the type of base they contain
- As a result, nucleotides are named after nitrogenous bases e.g. thymine nucleotide
