This topic summary covers Knowledge Organiser within DNA Genome for GCSE Biology. DNA structure, function, and the human genome It is section 12 of 13 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 12 of 13
Practice
25 questions
Recall
25 flashcards
Knowledge Organiser
Key Terms
- DNA — double helix of nucleotides
- Gene — section of DNA coding for a protein
- Chromosome — long coiled DNA molecule
- Genome — all genetic material of an organism
- Allele — version of a gene
- Complementary base pairing — A-T and C-G
- Genotype — alleles an organism carries
- Phenotype — observable characteristic
Must-Know Facts
- Humans have 46 chromosomes in 23 pairs
- Four DNA bases: A, T, C, G
- A pairs with T; C pairs with G (always)
- Genes code for amino acid sequences
- Proteins fold into 3D shapes that determine function
- Human Genome Project — completed 2003
- Most cells contain identical genomes
Protein Synthesis
- Transcription: DNA → mRNA (in nucleus)
- Translation: mRNA → protein (at ribosome)
- mRNA: single-stranded copy of one gene; uses uracil (U) not thymine
- Codon: 3 bases on mRNA = 1 amino acid
- Ribosome: assembles amino acids into a protein chain
- Mutation: change in DNA base sequence
- Chain: DNA → mRNA → amino acid sequence → protein shape → function
Common Marks Lost
- Confusing DNA (molecule) with gene (section of DNA)
- Saying chromosomes contain one gene — they contain thousands
- Wrong base pairs — remember A-T and C-G only
- Not explaining that base sequence determines amino acid sequence
- Forgetting that proteins fold to determine function
- Forgetting that mRNA uses uracil (U) not thymine (T)
- Not saying WHERE transcription (nucleus) and translation (ribosome) occur