Genetic information, variation and relationships between organisms – A Level AQA Biology revision notes

What this topic covers

Genetic information, variation and relationships between organisms has 7 subtopics, including:

• DNA, genes and chromosomes
• DNA and protein synthesis
• Genetic diversity can arise as a result of mutation or during meiosis
• Genetic diversity and adaptation
• Species and taxonomy
• Biodiversity within a community

Genetic information, variation and relationships between organisms lessons by subtopic

19 lessons, grouped by subtopic.

DNA, genes and chromosomes

• DNA, Genes, and the Genetic Code: Define a gene as a base sequence of DNA that codes for a specific amino acid sequence of a polypeptide; Explain the concept of a locus as the fixed position of a gene on a particular DNA molecule; Describe the triplet code and explain how a sequence of three DNA bases codes for a specific amino acid
• DNA Organisation: Prokaryotes vs. Eukaryotes: Compare the structure and organisation of DNA in prokaryotic and eukaryotic cells, including size, shape, and protein association; Explain why mitochondrial and chloroplast DNA resembles prokaryotic DNA in structure; Describe the relationship between DNA, histones, and chromosomes in eukaryotic nuclei
• Functional RNA: Explain the difference between coding and non-coding RNA, distinguishing functional RNA from mRNA; Describe the structure and role of ribosomal RNA (rRNA) in protein synthesis; Describe the structure and role of transfer RNA (tRNA) in protein synthesis

DNA and protein synthesis

• Transcription: From DNA to mRNA: Describe the process of transcription, including the role of RNA polymerase in joining mRNA nucleotides; Explain the difference between transcription in prokaryotes and eukaryotes; Explain the process of pre-mRNA splicing in eukaryotes to form mature mRNA
• Translation: mRNA to Polypeptides and the Genetic Code: Explain the process of translation, including the roles of mRNA, ribosomes, tRNA, and ATP; Relate the base sequence of mRNA codons to the amino acid sequence of a polypeptide using provided genetic code data; Describe the key features of the genetic code, including its triplet, degenerate, and non-overlapping nature
• Genome, Proteome, mRNA, and tRNA Structures: Define the genome and proteome, and describe the structures of mRNA and tRNA molecules.

Genetic diversity can arise as a result of mutation or during meiosis

• Meiosis & Genetic Variation: Describe the two nuclear divisions of meiosis and explain how four haploid daughter cells are produced from one diploid parent cell; Explain how independent segregation of homologous chromosomes generates genetic variation in daughter cells; Explain how crossing over between non-sister chromatids of homologous chromosomes produces further genetic variation
• Random Fertilisation & Chromosome Combinations: Recognise where meiosis occurs when given information about an unfamiliar life cycle; Explain how random fertilisation of haploid gametes further increases genetic variation within a species; Use the expression $2^n$ to calculate the possible number of different chromosome combinations following meiosis without crossing over
• Gene & Chromosome Mutations: Explain how base deletion and base substitution mutations alter the base sequence of DNA and the consequences for protein synthesis; Describe how the degenerate nature of the genetic code means not all base substitutions result in a change in amino acid sequence; Explain how mutagenic agents increase the rate of gene mutation

Genetic diversity and adaptation

• Genetic Diversity and Natural Selection: Explain how random mutation produces new alleles and how advantageous alleles increase in frequency over generations through natural selection; Define genetic diversity as the number of different alleles of genes in a population and explain its role in enabling natural selection; Describe the principles of natural selection and apply them to explain evolutionary change in a population
• Selection, Adaptation, and Evolution: Explain how natural selection produces changes in allele frequency within a population over time; Compare directional and stabilising selection using the examples of antibiotic resistance and human birth weight; Classify adaptations as anatomical, physiological, or behavioural and link each to survival advantage

Species and taxonomy

• Defining Species & Courtship Behaviour: State the biological species concept, using the criterion of fertile offspring production; Explain why courtship behaviour is a necessary precursor to successful mating; Describe the role of courtship in species recognition
• Phylogenetic Classification: Organising Life: Explain what a phylogenetic classification system is and why it is used to organise living organisms; State the eight taxa in the correct hierarchical order from domain to species; Apply the rules of binomial nomenclature to write and interpret species names correctly
• Modern Advances in Taxonomy: Discover how advances in immunology and genome sequencing contribute to our understanding of evolutionary relationships between organisms.

Biodiversity within a community

• Understanding Biodiversity and its Calculation: Define species richness and explain its limitations as a measure of biodiversity; Explain what an index of diversity measures and why it is more informative than species richness alone; Calculate an index of diversity using the formula $d = \frac{N(N-1)}{\Sigma n(n-1)}$ with accurate working
• Farming's Impact on Biodiversity: Explain how specific farming techniques reduce biodiversity at the species, habitat, and genetic level; Describe the mechanisms by which hedgerow removal, pesticide use, monoculture, and fertiliser application affect ecosystems; Evaluate the tension between maximising agricultural productivity and conserving biodiversity

Investigating diversity

• Measuring Diversity: Observable Traits & DNA: Describe how diversity within and between species can be measured using observable characteristics, DNA base sequences, mRNA base sequences, and amino acid sequences; Explain why direct investigation of DNA sequences has replaced inference from observable characteristics in measuring genetic diversity; Interpret data on DNA base sequences and amino acid sequences to suggest evolutionary relationships between organisms
• Quantitative Sampling Techniques: Explain why random sampling is essential for collecting unbiased data when investigating diversity; Describe how to use quadrats and transects to collect quantitative data from random samples; Calculate the mean and standard deviation of a data set collected from random samples
• Random Sampling Methods: Design appropriate methods to ensure random sampling within a biological investigation; Carry out random sampling within a single population using appropriate techniques; Analyse data from random samples to investigate the effect of position on leaf growth

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