Exam Tips: Genetic Inheritance
Part of Genetic Inheritance — GCSE Biology
This exam tips covers Exam Tips: Genetic Inheritance within Genetic Inheritance for GCSE Biology. Genetic inheritance patterns, alleles, and inheritance diagrams It is section 9 of 9 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 9 of 9
Practice
25 questions
Recall
25 flashcards
Exam Tips: Genetic Inheritance
Always show your gametes: Before filling in the Punnett square, write the gametes along the top and side. These carry method marks — even if you fill the grid incorrectly, you can still earn marks for correct gametes.
State both ratio and probability: After completing a Punnett square, give the genotype ratio (e.g., 1 BB : 2 Bb : 1 bb) AND the phenotype ratio (e.g., 3 brown : 1 blue). Then give the probability as a fraction and percentage.
Dominant does not mean common: This is one of the most common misconceptions — explicitly say "dominant means it is expressed when one copy is present" rather than "dominant means it is more frequent".
Carrier definition: A carrier is always heterozygous (one dominant, one recessive allele) for a recessive condition. They do not show the condition. If asked to define "carrier", include all three elements: heterozygous, does not show symptoms, can pass the recessive allele to offspring.
Letter choice matters: Use letters that look different in upper and lower case. Avoid letters like C/c, O/o, P/p where upper and lower can look similar. Good choices: B/b, T/t, F/f, H/h.