Identify the correct statement(s). In prokaryotes:

Correct Answer: d

Rationale: The correct answer is D because in prokaryotes, 50s and 30s ribosomal subunits combine to form the 70s ribosome, which is necessary for protein synthesis. Firstly, ribosomes are composed of two subunits, and in prokaryotes, these are the 50s and 30s subunits. Secondly, these subunits come together during translation to form the functional ribosome. Therefore, these ribosomal subunits are indeed necessary for protein synthesis in prokaryotes. A: Incorrect. Translation can begin before transcription is finished in prokaryotes due to their lack of a nuclear membrane. B: Incorrect. Messenger RNA in prokaryotes is co-linear with the DNA template as they do not undergo RNA splicing like eukaryotes. C: Incorrect. In prokaryotes, the ribosomal RNA present is the 16s, 23s, and 5s, not 28s.

Correct Answer: C

Rationale: Rationale for Answer C: 1. Allergen exposure triggers B cells to produce IgE antibodies specific to the allergen. 2. IgE antibodies bind to mast cells sensitizing them. 3. Upon re-exposure to allergen, allergen binds to IgE on mast cells. 4. This triggers release of histamine and other chemicals causing allergic symptoms. Summary: - Choice A: Incorrect because B cells do not produce IgE antibodies before allergen exposure. - Choice B: Incorrect because IgE antibodies are produced by B cells, not the other way around. - Choice D: Incorrect because histamine is released after allergen binds to IgE on sensitized mast cells.

Correct Answer: C

Rationale: The correct answer is C because methylation of DNA typically results in the inhibition or slowing down of transcription. Methylated DNA attracts proteins that bind to it, preventing transcription factors from accessing the DNA and initiating transcription. This interference with the transcription process leads to gene silencing or reduced gene expression. A: DNA unwinding in preparation for protein synthesis is unrelated to DNA methylation. B: Continuous replication is not a typical consequence of DNA methylation. D: Methylation does not directly induce protein synthesis but rather affects transcription by influencing gene expression.

Correct Answer: D

Rationale: The correct answer is D because Taq polymerase is heat-stable, allowing it to withstand the high temperatures used in PCR cycles without denaturing. This heat stability is crucial for the repeated heating and cooling cycles in PCR. Choice A is incorrect because Taq polymerase does not need to be complementary to primers. Choice B is incorrect because the amount needed is not the main reason for using Taq polymerase. Choice C is incorrect because binding affinity to primers is not the primary reason for using Taq polymerase.

Correct Answer: D

Rationale: In the context of immune system disorders, the correct answer to the question is D) Lymphocytes. Lymphocytes are a type of white blood cell that is small in size, present in the blood, and has the ability to migrate to tissues as needed. Lymphocytes play a crucial role in the adaptive immune response, recognizing and attacking specific pathogens. They are key players in producing antibodies and coordinating immune responses to infections. Now, let's analyze why the other options are incorrect: A) Neutrophils: Neutrophils are also a type of white blood cell, but they are not primarily known for migrating to tissues as necessary. They are more involved in the initial response to infections by engulfing pathogens. B) Leukocytes: Leukocytes is a broad term that encompasses all white blood cells, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils. While lymphocytes are a type of leukocyte, the term itself is too general to be the correct answer in this context. C) Monocytes: Monocytes are another type of white blood cell that can migrate to tissues and differentiate into macrophages or dendritic cells. However, they are not the primary cells known for this specific function described in the question. In an educational context, understanding the functions and characteristics of different white blood cells is essential for diagnosing and treating immune system disorders. Knowing the specific roles of lymphocytes, neutrophils, monocytes, and other leukocytes helps healthcare professionals make informed decisions in managing patients with immune-related conditions.