Inheritance — OCR GCSE Biology
Test yourself on Inheritance with OCR GCSE practice questions.
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Inheritance explained
Mastery of genetics requires precise biological terminology.
Read the full explanation
A gamete is a haploid sex cell. Chromosomes are linear structures of coiled DNA carrying genes, found in the nucleus. A gene is a section of DNA that codes for a specific sequence of amino acids to produce a protein. Alleles are alternative versions of a gene. A dominant allele is expressed if one or two copies are present, whereas a recessive allele is expressed only when homozygous. Homozygous indicates identical alleles; heterozygous indicates two different alleles. Genotype is the genetic makeup; phenotype is the observable physical characteristic.
Your focus
- Define fundamental genetic terms including gamete, chromosome, gene, allele, genotype, and phenotype.
- Contrast homozygous and heterozygous genotypes and explain the expression of dominant and recessive alleles.
- Apply accurate genetic vocabulary to describe the transmission and physical manifestation of traits.
Inheritance exam tips
Marking Points
- Define a gene as a section of DNA coding for a sequence of amino acids to make a specific protein.
- Distinguish between homozygous (two identical alleles) and heterozygous (two different alleles).
- Explain that a dominant allele is expressed in the phenotype when present, while a recessive allele requires two copies to be expressed.
- Define genotype as the combination of alleles present, and phenotype as the observable physical characteristics.
Examiner Tips
- 💡Use the exact definition for gene: a section of DNA that codes for a specific protein or sequence of amino acids.
- 💡When defining phenotype, mention that it is the physical expression resulting from genotype and environmental interactions.
Common Mistakes
- Confusing gene and allele, referring to an allele as a whole gene rather than an alternative variant of a gene.
- Describing a dominant allele as stronger or more common in a population rather than an allele that is expressed over a recessive one.