Inheritance: DNA
17.2 DNA
Structure Of DNA
- Two strands coiled into a double helix.
- Each strand = chain of nucleotides.
- Each nucleotide = base (A, T, C, G) + sugar + phosphate.
- Base pairing:
- A pairs with T.
- C pairs with G.
- Bases held together by hydrogen bonds.
Genes
- Gene = length of DNA that codes for a protein.
- Sequence of bases determines sequence of amino acids.
- Different amino acid sequences → different protein shapes/functions.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course
DNA Function
- Controls cell activity by controlling protein production (e.g., enzymes, hormones, structural proteins).
- Mutations in DNA sequence → can change protein shape and function.
Key Points
- DNA found in nucleus (chromosomes).
- Genetic code is universal in living organisms.
- Proteins determine characteristics of an organism.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course