2.4 Genome, Chromosomes, DNA and Genetics
Genome organisation, DNA structure, protein synthesis, mitosis and meiosis, genetic diagrams, sex determination, screening and engineering.
How to study for CCEA GCSE Biology
Learn each process as a structure-and-mechanism chain, use data with units, and prepare every prescribed practical from planning through conclusion and evaluation.
Core concepts
Concept 1
A genome contains an organism's genetic material; chromosomes carry DNA, genes are functional DNA sections and alleles are alternative forms of a gene.
Exam cue: Move between genome, chromosome, DNA, gene, allele and protein without treating the levels as synonyms.
Concept 2
Base sequence carries information used to assemble proteins, while mitosis preserves chromosome number and meiosis produces varied haploid gametes.
Exam cue: Show parental genotypes, gametes and offspring genotypes before giving a phenotypic probability.
Concept 3
Monohybrid crosses use allele notation, gametes and probability to predict offspring, while observed ratios can vary through chance.
Exam cue: For screening or genetic engineering, separate what the method can reveal or change from ethical and risk judgements.
Risk pitfalls and guardrails
Calling a gene a whole chromosome or an allele a different characteristic.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a biological mechanism with a vague purpose statement.
Treating a predicted genetic ratio as a guaranteed result for a small family.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a biological mechanism with a vague purpose statement.
Saying meiosis makes two genetically identical diploid cells.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a biological mechanism with a vague purpose statement.
Memory anchors
Genome
All the genetic material of an organism.
Gene
A DNA section that functions as a unit controlling a characteristic through a product.
Allele
An alternative form of the same gene.
Mitosis
Cell division producing genetically identical cells with the chromosome number maintained.
Meiosis
Cell division producing genetically varied haploid gametes.
Monohybrid cross
A genetic cross following one characteristic controlled by one gene with two alleles.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What is a genome?
A DNA diagram highlights a sequence that has a particular biological function. What term describes the highlighted sequence?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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