Genetic vocabulary and basic inheritance (Part 1/2) Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Learn key genetic terms including gamete, chromosome, gene, allele, dominant, recessive, homozygous, heterozygous, genotype and phenotype. Understand ho...

• Define key genetic terms including gamete, chromosome, gene, and allele
• Distinguish between dominant and recessive alleles in inheritance patterns
• Compare homozygous and heterozygous genotypes
• Explain the relationship between genotype and phenotype

Key ideas to keep in view

Use this lesson to stay inside B5.1 Inheritance while connecting the detail back to the wider B5: Genes, inheritance and selection topic.

• B5: Genes, inheritance and selection
• B5.1 Inheritance
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from Genetic vocabulary and basic inheritance (Part 1/2) before testing yourself from memory.

• Why do you have your mum's eyes but your dad's nose? The answer lies in tiny structures inside every cell that carry the instructions for making you. These instructions are passed from parents to children through reproduction, but the language of genetics has specific terms we need to master first.
• A reproductive cell (sperm or egg) that contains half the normal number of chromosomes
• A structure made of DNA that contains many genes, found in the nucleus of cells
• Trap: Many students think chromosomes and genes are the same thing. Actually, chromosomes are like books, and genes are individual chapters within those books. Humans have 46 chromosomes (23 pairs), but thousands of genes.
• Now we zoom in further. Each chromosome contains hundreds of genes, and this is where inheritance gets interesting. Think of genes as recipes for making proteins, but like any recipe, there can be different versions.
• A section of DNA that codes for a particular characteristic, such as eye colour or blood group
• Different versions of the same gene that control the same characteristic but may produce different traits
• Here's the key insight: you inherit two copies of each gene - one from each parent. These copies might be identical, or they might be different versions (alleles). For example, the gene for eye colour has different alleles - one for brown eyes, one for blue eyes.
• 3. Dominant vs Recessive - The Power Struggle
• When you have two different alleles for the same gene, which one wins? This is where dominance comes in. Some alleles are bossy - they always get their way. Others are quiet - they only show up when the bossy one isn't around.

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.