Eduqas GCSE Biology 7 Inheritance, Variation and Evolution Exam Questions

About Eduqas GCSE Biology 7 Inheritance, Variation and Evolution

Inheritance, variation and evolution is the final Eduqas GCSE Biology topic, with four parts: the genome and gene expression, inheritance, variation and evolution, and selective breeding and gene technology. You learn DNA structure, base pairing and protein synthesis, genetic profiling, genetic terminology, Punnett squares and sex determination, and the work of Mendel, Darwin and Wallace. Evolution covers mutation, natural selection, evidence such as antibiotic resistance and warfarin-resistant rats, and the three-domain classification system. It finishes with selective breeding and genetic engineering. Examiners regularly set genetic cross diagrams with probabilities, natural selection explanations and ethics questions on gene technology. SP7.1 is extracting DNA from living material.

What you need to know

• 7.1 DNA structure DNA is a double helix made of nucleotides, each with a sugar, a phosphate and a base. Bases pair A with T and C with G. A triplet of bases codes for one amino acid, and the order of triplets determines the protein made.
• 7.1 Gene expression and profiling Much DNA is non-coding and some controls which genes are switched on. Genetic profiling cuts DNA into fragments and compares the banding patterns, for example in forensics and paternity. SP7.1: simple extraction of DNA from living material.
• 7.2 Genetic terms and crosses Know gamete, gene, allele, dominant, recessive, homozygous, heterozygous, genotype and phenotype. Use Punnett squares for monohybrid crosses: two heterozygous parents give a 3:1 ratio of dominant to recessive phenotypes. Most characteristics are polygenic.
• 7.2 Sex and Mendel Females are XX and males are XY, giving a 50% chance of either sex. Mendel worked out the patterns of inheritance using pea plants; his work was not recognised at first because genes and chromosomes had not been discovered.
• 7.3 Variation and natural selection Variation is caused by genes, the environment or both. Mutations arise randomly and are more likely with ionising radiation. Individuals with advantageous variations survive, reproduce and pass on their alleles. Evidence includes fossils, antibiotic-resistant bacteria and warfarin-resistant rats.
• 7.3 Classification The three-domain system separates archaea, bacteria and eukaryotes; eukaryotes include the protist, fungi, plant and animal kingdoms. Darwin and Wallace independently proposed evolution by natural selection.
• 7.4 Gene technology Selective breeding chooses parents with desired characteristics over many generations, which can reduce genetic variation. Genetic engineering transfers a gene from one organism into another, for example crops resistant to pests; it has benefits in agriculture and medicine but raises practical and ethical concerns.

Common mistakes in 7 Inheritance, Variation and Evolution

• Saying that organisms mutate in order to adapt. Mutations are random; natural selection then favours those individuals that happen to have useful variations.
• Mixing up genotype and phenotype. Genotype is the alleles (for example Bb); phenotype is the characteristic that shows (for example brown eyes).
• Giving the probability of the recessive phenotype from a heterozygous cross as 3 in 4. It is 1 in 4, or 25%.
• Writing that a gene codes for a characteristic directly. A gene is a section of DNA that codes for a protein, which then affects a characteristic.
• Confusing selective breeding with genetic engineering. Selective breeding uses natural reproduction over generations; genetic engineering moves genes directly between organisms.

Try three 7 Inheritance, Variation and Evolution exam-style questions