NBME 28 1-40

Apuntes

• Subtopic: Lesch-Nyhan Syndrome and Population Genetics Lesch-Nyhan syndrome, an X-linked recessive disease, is seen in approximately 1 in 100,000 males. Which of the following is the expected prevalence of heterozygous females? A) 1/100 B) 1/150 C) 1/200 D) 1/1,000 **Correct Answer: B** The Hardy-Weinberg principle states that allele frequencies in a population will remain constant across generations in the absence of evolutionary change. The Hardy-Weinberg equilibrium equation is p² + 2pq + q² = 1, where p is the frequency of the dominant allele and q is the frequency of the recessive allele. If q = 1/100, then p = 1 - q = 1 - 0.01 = 0.99. The probability of being a heterozygote (2pq) is then 2(0.99)(0.01) = 0.0198 or approximately 1 in 50. Therefore, the expected prevalence of heterozygous females is 1 in 150. --- • Subtopic: Liver Lesion in a 65-Year-Old Man The specimen shown is from a 65-year-old man. Which of the following is the most likely diagnosis? A) Acute leukemia B) Colonic carcinoma C) Hepatic cell carcinoma D) Liposarcoma E) Lymphoma **Correct Answer: B** Colonic carcinoma, also known as colorectal carcinoma (CRC), is the most lik...