Genetic Disorders — GCSE Biology Revision
Revise Genetic Disorders for GCSE Biology. Step-by-step explanation, worked examples, common mistakes and exam-style practice aligned to AQA, Edexcel, OCR, WJEC, Eduqas, CCEA, Cambridge International (CIE), SQA, IB, AP.
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Go to Selective BreedingWhat is Genetic Disorders?
Genetic disorders are conditions caused by abnormalities in an individual's DNA. Some are inherited from parents, caused by faulty alleles, such as cystic fibrosis (a recessive disorder) and polydactyly (a dominant disorder). These can be traced through family trees to predict the probability of inheritance.
Board notes: Covered by all major boards (AQA, Edexcel, OCR). Students should be able to use Punnett squares to predict the inheritance of single-gene disorders like cystic fibrosis and polydactyly.
Step-by-step explanationWorked example
Cystic fibrosis is a recessive disorder. If two parents are both carriers (Cc), there is a 25% chance (1 in 4) of them having a child with cystic fibrosis (cc), a 50% chance of having a carrier child (Cc), and a 25% chance of having an unaffected child (CC). This can be shown with a Punnett square.
Mini lesson for Genetic Disorders
1. Understand the core idea
Genetic disorders are conditions caused by abnormalities in an individual's DNA. Some are inherited from parents, caused by faulty alleles, such as cystic fibrosis (a recessive disorder) and polydactyly (a dominant disorder).
Can you explain Genetic Disorders without copying the notes?
2. Turn it into marks
Cystic fibrosis is a recessive disorder. If two parents are both carriers (Cc), there is a 25% chance (1 in 4) of them having a child with cystic fibrosis (cc), a 50% chance of having a carrier child (Cc), and a 25% chance of having an unaffected child (CC).
Underline the method, evidence, or command-word move that would earn credit in GCSE Inheritance, Variation & Evolution.
3. Fix the likely mark leak
Watch for this mistake: Assuming all genetic disorders are inherited. While many are, some can arise from spontaneous mutations in the DNA during an individual's lifetime.
Write one correction rule before doing another practice question.
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Genetic Disorders practice questions
These are original StudyVector questions for revision practice. They are not official exam-board questions.
Question 1
In one GCSE sentence, explain what Genetic Disorders is testing.
Answer: Genetic disorders are conditions caused by abnormalities in an individual's DNA. Some are inherited from parents, caused by faulty alleles, such as cystic fibrosis (a recessive disorder) and polydactyly (a dominant disorder).
Mark focus: Precise definition and topic focus.
Question 2
A Genetic Disorders question uses an unfamiliar context. What should the answer do before adding detail?
Answer: It should name the process, variable, equation, particle model, or evidence being tested, then explain the result using precise scientific vocabulary.
Mark focus: Method selection and command-word control.
Question 3
A student makes this mistake: "Assuming all genetic disorders are inherited. While many are, some can arise from spontaneous mutations in the DNA during an individual's lifetime." What should their next repair task be?
Answer: Do one Genetic Disorders question and review the mistake type.
Mark focus: Error correction and next-step practice.
Genetic Disorders flashcards
Core idea
What is the main idea in Genetic Disorders?
Genetic disorders are conditions caused by abnormalities in an individual's DNA. Some are inherited from parents, caused by faulty alleles, such as cystic fibrosis (a recessive disorder) and polydactyly (a dominant di...
Common mistake
What mistake should you avoid in Genetic Disorders?
Assuming all genetic disorders are inherited. While many are, some can arise from spontaneous mutations in the DNA during an individual's lifetime.
Practice
What is one useful practice task for Genetic Disorders?
Answer one Genetic Disorders question and review the mistake type.
Exam board
How should you use board notes for Genetic Disorders?
Covered by all major boards (AQA, Edexcel, OCR). Students should be able to use Punnett squares to predict the inheritance of single-gene disorders like cystic fibrosis and polydactyly.
Common mistakes
- 1Assuming all genetic disorders are inherited. While many are, some can arise from spontaneous mutations in the DNA during an individual's lifetime.
- 2Confusing recessive and dominant disorders. For a recessive disorder like cystic fibrosis to be expressed, an individual must inherit two faulty alleles (cc). For a dominant disorder like polydactyly, only one faulty allele (P) is needed.
- 3Thinking that being a 'carrier' means you have the disorder. A carrier is heterozygous for a recessive disorder (e.g., Cc for cystic fibrosis). They do not have the disorder themselves but can pass the faulty allele on to their children.
Genetic Disorders exam questions
Exam-style questions for Genetic Disorders with mark-scheme style solutions and timing practice. Aligned to AQA, Edexcel, OCR, WJEC, Eduqas, CCEA, Cambridge International (CIE), SQA, IB, AP specifications.
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Step-by-step method
Step-by-step explanation
4 steps · Worked method for Genetic Disorders
Core concept
Genetic disorders are conditions caused by abnormalities in an individual's DNA. Some are inherited from parents, caused by faulty alleles, such as cystic fibrosis (a recessive disorder) and polydacty…
Frequently asked questions
What is cystic fibrosis?
Cystic fibrosis is an inherited disorder that affects cell membranes, causing the body to produce thick, sticky mucus. This can lead to problems with the lungs and digestive system.
What is embryonic screening?
Embryonic screening is a process where embryos created through IVF are genetically tested for certain disorders before being implanted. It allows parents with a known risk of passing on a genetic disorder to select a healthy embryo.