Decitabine increases the fetal hemoglobin production by inducing methylation of DNA and thus prevents the switch from gamma to beta-globin production.

Correct Answer: B

Rationale: Step 1: Decitabine is a DNA methyltransferase inhibitor, NOT an inducer. Step 2: Fetal hemoglobin production is regulated by gene expression, not DNA methylation. Step 3: The switch from gamma to beta-globin production is primarily controlled by transcription factors. Step 4: Therefore, the statement that decitabine prevents the switch by inducing DNA methylation is FALSE. Summary: Choice B is correct because decitabine does not induce DNA methylation to increase fetal hemoglobin production. Choices A, C, and D are incorrect due to the lack of evidence supporting them.

Correct Answer: B

Rationale: The correct answer is B: Older adults. Chronic lymphocytic leukemia typically affects individuals over the age of 50, with the average age of diagnosis around 70. This type of leukemia is rare in young adults, children, or middle-aged adults. Risk factors for chronic lymphocytic leukemia include advanced age and a family history of the disease. Therefore, older adults are the most commonly affected demographic group for this type of leukemia.

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: D

Rationale: The correct answer is D because the lipids in the RBC membrane are arranged in a phospholipid bilayer structure, with two layers that are not symmetric in composition. This asymmetry is crucial for maintaining the integrity and function of the membrane. The inner and outer layers have different lipid compositions, allowing for specific functions such as signal transduction and selective permeability. Choice A is incorrect because lipids are not arranged in chains beneath a protein exoskeleton in the RBC membrane. Choice B is incorrect because the hydrophobic portions of lipids face each other within the membrane, not the plasma. Choice C is incorrect as lipids are not arranged in a hexagonal lattice in the RBC membrane.

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.