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Randy Neil Biostats 26: Test Your Knowledge of Genetics and Pedigree
Episode Notes
USMLE purpose: Review genetics and pedigree-style probability questions using a clean inheritance-pattern workflow.
How to use this page
- Identify the inheritance pattern first.
- Determine carrier/affected status for each parent.
- Write the Punnett-style probability before choosing an answer.
- Use the toggles as rapid recall.
Episode metadata
| Field | Details |
| Episode | Randy Neil Biostats 26 |
| Topic | Genetics and pedigree questions |
| Runtime | 11 min |
| Published | 2024-02-04 |
| Source | Open YouTube video |
One-liner
Pedigree questions are probability questions: identify the inheritance pattern, assign parent genotypes, then multiply independent probabilities.
Inheritance recognition table
| Pattern | Classic clue | Risk shortcut |
| Autosomal dominant | Vertical transmission; affected parent often affected child | Heterozygous affected parent → 50% affected children |
| Autosomal recessive | Skipped generations; siblings affected | Two carrier parents → 25% affected, 50% carrier |
| X-linked recessive | Mostly males; no father-to-son transmission | Carrier mother → 50% affected sons |
| Mitochondrial | Maternal transmission | Affected mother can transmit to all children |
Anki-style rapid recall
What is the risk of an affected child from two autosomal recessive carriers?
25% affected, 50% carrier, 25% unaffected non-carrier.
What inheritance pattern has no father-to-son transmission?
X-linked inheritance.
What pattern suggests mitochondrial inheritance?
Transmission through affected mothers to children.
Practice Question
Two unaffected parents have an affected child with an autosomal recessive disorder. What is the chance their next child is affected?
- A) 0%
- B) 25%
- C) 50%
- D) 75%
Reveal answer & explanation
Answer: B) 25%
Unaffected parents with an affected autosomal recessive child are presumed carriers; carrier × carrier gives 25% affected risk.