ombinations is $2^9 = 512$.","order":2},{"id":"e0111956-19d1-487b-ab29-3578e2a1264d","content":"$$262,144$","correct":false,"markscheme":"The student forgot to divide the diploid chromosome number by 2 to find the number of pairs, calculating $2^{18}$ instead of $2^9$.","order":3}],"explanation":null,"firstAttemptFullMarks":null},{"id":"18dd6812-18bb-4e56-8673-a86a0bfd21c7","revisionId":"929c351e-4fdb-4e5b-a3e8-948ca3723256","questionNumber":null,"questionType":"LA","specification":"Huntington's disease is an inherited neurodegenerative disorder caused by a dominant allele.","difficulty":4,"difficultyBand":"medium","totalMarks":5,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"50d5e31c-384b-4deb-9e95-858e30ac1bfd","label":"a","content":"Arrange the terms **DNA nucleotide**, **gene**, and **chromosome** in order of size, starting with the **largest**.","markscheme":"- Identifies the correct order from largest to smallest: chromosome, gene, DNA nucleotide B1","marks":1,"order":0,"markingRubric":null,"explanation":{"methods":[{"id":"size_order","label":"Order the genetic structures","steps":[{"type":"text","order":0,"title":"Order the sizes","content":"Start with the largest term and work down:\n\n$$\\boxed{\\text{chromosome} \\;\\rightarrow\\; \\text{gene} \\;\\rightarrow\\; \\text{DNA nucleotide}}$$\n\nA chromosome contains many genes. Each gene is a section of DNA made from many DNA nucleotides, so the chromosome is largest and the DNA nucleotide is smallest.\n\n**Examiner note:** This correct largest-to-smallest order earns B1.","highlights":[{"text":"Arrange the terms **DNA nucleotide**, **gene**, and **chromosome** in order of size, starting with the **largest**.","location":"specification"}]}]}],"generatedAt":"2026-07-22T11:13:43.488Z","modelVersion":"gpt-5.6-terra+diagrams-1","explanationVersion":"v3"},"options":[]},{"id":"f54609d2-5aaf-4c8e-854c-20a8c751c843","label":"b","content":"Approximately 1 in 12,000 people in a certain population have Huntington's disease. In a city with a population of 1,800,000, calculate how many people are expected to have Huntington's disease.","markscheme":"- Sets up calculation: $\\frac{1,800,000}{12,000}$ or equivalent M1\n- Calculates $150$ A1","marks":2,"order":1,"markingRubric":null,"explanation":{"methods":[{"id":"population_rate","label":"Apply the population rate","steps":[{"type":"hyper_latex","block":{"nodes":[{"latex":"\\text{expected number}=\\frac{1\\,800\\,000}{12\\,000}"},{"text":"The denominator is 12,000 because there is one expected case for every 12,000 people."}]},"order":0,"title":"Set up the division","description":"Divide the total population by the number of people represented by each case. This correct setup earns the M1 mark."},{"type":"text","order":1,"title":"Calculate the expectation","content":"$$$\\frac{1\\,800\\,000}{12\\,000}=150$$\n\nSo **150 people** are expected to have Huntington's disease. This correct calculation earns the A1 mark."}]}],"generatedAt":"2026-07-22T11:30:56.009Z","modelVersion":"gpt-5.6-terra+diagrams-1","explanationVersion":"v3"},"options":[]},{"id":"c3a1accc-1c2e-4dac-a9c7-25f441a04727","label":"c","content":"A man who is heterozygous for Huntington's disease ($\\text{Hh}$) and a woman who is also heterozygous ($\\text{Hh}$) are expecting a baby. State the probability that their baby will inherit Huntington's disease.","markscheme":"- Identifies that offspring with genotypes $\\text{HH}$ or $\\text{Hh}$ will inherit the disease M1\n- States the probability is $0.75$ (or $\\frac{3}{4}$ or $75\\%$) A1","marks":2,"order":2,"markingRubric":null,"explanation":{"methods":[{"id":"punnett_square","label":"Use a Punnett square","steps":[{"type":"drawing","order":0,"title":"Set up the cross","width":565,"height":228,"shapes":[{"id":"tbl-border","type":"line","color":"black","points":[{"x":42,"y":186},{"x":523.2,"y":186},{"x":523.2,"y":42},{"x":42,"y":42},{"x":42,"y":186}]},{"id":"tbl-v1","type":"line","color":"grey","points":[{"x":209.8,"y":186},{"x":209.8,"y

Inheritance

Question 5

Inheritance Questions

Inheritance

Question 5

Inheritance Questions