A 1:20 dilution was made in a unopette, with glacial acetic acid as the diluent. The four corner squares on BOTH sides of the hemacytometer are counted for a total of 100 cells. What is the total WBC (x10^9/L)?

Correct Answer: B

Rationale: The correct answer is B: 2.5. The dilution factor for the hemacytometer is 20, so we must multiply the count of 100 cells by 20 to get the total number of cells per microliter. Given the dilution factor, we then convert cells per microliter to cells per liter by multiplying by 10^6. To convert cells per liter to cells per cubic meter, we multiply by 10^3. Finally, to convert cells per cubic meter to x10^9/L, we divide by 10^9. The correct calculation is (100 cells * 20 * 10^6 * 10^3) / 10^9 = 2.5 x10^9/L. Summary: A: 0.25 - Incorrect, as it does not account for the dilution factor and the subsequent conversions. C: 5 - Incorrect, as it is the result of a miscalc

Correct Answer: B

Rationale: The correct answer is B because the globin chain genes are indeed located on separate chromosomes. The alpha (a) genes are located on one chromosome, while the beta (B) genes are located on a different chromosome. This arrangement allows for independent regulation and expression of the alpha and beta globin chains. Choices A, C, and D are incorrect because they do not accurately reflect the known genetic arrangement of the globin chain genes. Choice A incorrectly states that both a and B genes are on the same chromosome, which is not the case. Choice C is incorrect as it states that there are four a genes and four B genes, which is not accurate. Choice D is incorrect as it states that there are four a genes on one chromosome and two B genes on a different chromosome, which is also inaccurate.

Correct Answer: B

Rationale: The correct answer is B (25%). When both parents are carriers of the sickle cell trait, they each pass down the gene for sickle cell or normal hemoglobin with a 50% chance. The possible combinations are SS (normal), SS (sickle cell disease), AS (sickle cell trait), or AS (sickle cell trait). Therefore, there is a 25% chance (1 out of 4) that their child will inherit two sickle cell genes and have sickle cell anaemia. Choices A, C, and D are incorrect as they do not accurately reflect the genetic probability based on Mendelian inheritance principles.

Correct Answer: B

Rationale: The most likely diagnosis is B: Deep vein thrombosis (DVT). In a post-hip replacement patient with painful, pale, and swollen calf, DVT is common due to immobility and hypercoagulability. DVT presents with unilateral swelling, pain, and discoloration. Acute limb ischemia (A) typically presents with sudden severe pain, pallor, pulselessness, and paralysis. Cellulitis (C) presents with redness, warmth, and tenderness, not pallor. Fracture complication (D) would typically present with localized pain and swelling at the fracture site, not in the calf region.

Correct Answer: A

Rationale: The correct answer is A: potentially lethal graft-versus-host disease. Bone marrow transplantation in immunocompromised patients can lead to graft-versus-host disease, where the donor's immune cells attack the recipient's tissues, potentially leading to severe complications or death. This occurs due to the recognition of the recipient's tissues as foreign by the donor's immune system. The other choices are incorrect because B (high risk of T cell leukemia) is not a major problem associated with bone marrow transplantation, C (inability to use a live donor) is not a major problem but a limitation, and D (delayed hypersensitivity) is not a major concern in this context.