USMLE Step 1 Genetics Quiz with complete solutions | Latest 2023/2024

USMLE Step 1 Genetics Quiz with complete solutions | Latest 2023/2024 Autosomal dominant -- AD Often due to defects in structural genes; *every* generation, both male and female, affected Family history crucial to diagnosis Autosomal recessive -- AR 25% of offspring from 2 carrier parents are affected; often due to enzyme deficiencies; usually seen in only 1 generation or it *skips* a generation commonly more severe than dominant disorders; patients often present in childhood consanguineous -1st cousins; sharing similar ancestry X-linked recessive -- XR *Sons* of heterozygous mothers have a 50% chance of being affected; no male-to-male transmission (because father needs to give son a Y chromosome for him to be a 'boy') Commonly more severe in males; heterozygous females may be affected X-linked dominant -- XD Transmitted through both parents; either male or female offspring of the affected mother may be affected, while *all* female offspring of an affected father are diseased *hypophosphatemic rickets* known as vitamin D-resistant rickets; inherited disorder resulting in ↑ phosphate wasting at proximal tubule; results in rickets-like presentation *fragile x syndrome* Mitochondrial inheritance -- Transmitted only through *mother*; *all offspring* of affected females may show signs of disease Variable expression population due to heteroplasmy