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Biology · AQA Paper 2

DNA and the Genome

How DNA carries the genetic code: the structure of DNA, chromosomes, genes and the genome, and why the human genome matters. For separate Biology it goes on to the nucleotides and bases that make up DNA, and for Higher tier students it covers protein synthesis, mutations and non-coding DNA. Matches AQA topic 4.6.1.4 (DNA and the genome) and 4.6.1.5 (DNA structure, separate Biology only). The first lesson is for both Combined Science and separate Biology; the other lessons are for separate Biology only, and the Higher tier parts are marked.

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Lessons

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Key terms in this chapter

All 33, gathered from every lesson.

DNA
The chemical in the nucleus that carries the genetic code, a polymer made of two strands forming a double helix.
Double helix
The shape of DNA: two strands coiled around each other.
Polymer
A large molecule made of many repeating units joined together.
Chromosome
A structure in the nucleus, made of one long molecule of DNA, that carries many genes.
Gene
A small section of DNA on a chromosome that codes for a particular sequence of amino acids, to make a specific protein.
Genome
The entire genetic material of an organism.
Amino acid
A small molecule that is joined in a chain with others to make a protein.
Protein
A molecule made of a chain of amino acids, such as an enzyme, a hormone or collagen.
Nucleotide
One unit of DNA: a sugar, a phosphate group and one base.
Base
The part of a nucleotide that carries the code: A, C, G or T.
Phosphate group
The part of a nucleotide that joins to the sugar of the next nucleotide to form the backbone.
Sugar-phosphate backbone
The alternating sugar and phosphate sections that run along each strand of DNA.
Triplet
A sequence of three bases that codes for one amino acid.
Complementary base pairs
The pairs C with G and T with A that link the two strands of DNA together (Higher tier).
Polymer
A long molecule made of many repeating units.
Amino acid
A small molecule that joins with others to make a protein.
Protein synthesis
The making of a protein, on a ribosome, by joining amino acids in the order given by a gene.
Ribosome
A tiny structure in the cytoplasm where proteins are made.
Template
A copy of the gene that the ribosome reads to put amino acids in the right order.
Carrier molecule
A molecule that brings a specific amino acid to the ribosome.
Amino acid
A small molecule that is joined in a chain with others to make a protein.
Enzyme
A protein that speeds up a chemical reaction.
Hormone
A protein or other chemical messenger carried in the blood.
Collagen
A structural protein that forms strong fibres in skin, tendons and bones.
Mutation
A change in the base sequence of DNA.
Substitution
A mutation in which one base is replaced by a different base.
Insertion
A mutation in which an extra base is added to the DNA.
Deletion
A mutation in which a base is lost from the DNA.
Active site
The part of an enzyme into which the substrate fits.
Substrate
The substance that an enzyme acts on.
Non-coding DNA
Parts of DNA that do not code for proteins and can switch genes on and off.
Genetic variant
A different version of a DNA sequence, which arose by mutation.
Gene expression
The switching on of a gene so that its protein is made.