The actual genetic makeup of an organism is referred to as its

Correct Answer: B

Rationale: The correct answer is B: genotype. The genotype refers to the actual genetic makeup of an organism, including all the genes and alleles present in its DNA. This determines the traits and characteristics of an organism. Phenotype (A) is the observable physical or biochemical characteristics of an organism. Conjugation (C) is a process in bacteria involving the transfer of genetic material. Construct (D) is not a term related to genetics. Therefore, the correct choice is B as it specifically refers to the genetic composition of an organism.

Correct Answer: D

Rationale: The correct answer is D: Gram-negative bacteria without peptidoglycan. Chlamydia is an intracellular, gram-negative bacteria that lacks peptidoglycan in its cell wall. Peptidoglycan is a key component of the cell wall in most bacteria, but Chlamydia has a unique structure without it. This makes it different from choices A, B, and C, which describe characteristics not applicable to Chlamydia. Choice A is incorrect because Chlamydia is not a gram-positive coccobacteria. Choice B is incorrect because Chlamydia does have a cell wall, albeit lacking peptidoglycan. Choice C is incorrect because Chlamydia is not a gram-negative bacteria with little peptidoglycan, but rather without it.

Correct Answer: A

Rationale: The correct answer is A: Treponema pallidum. This is because Treponema pallidum is a thin spiral bacteria with 12-14 coils and pointed ends, which matches the description given in the question. Treponema pallidum is the causative agent of syphilis. Choices B, C, and D are incorrect: B: Leptospira - Leptospira is a spiral-shaped bacteria, but it does not have the specific characteristics mentioned in the question. C: Borrelia - Borrelia is another spiral-shaped bacteria, but it does not match the specific features described in the question. D: Spirochaeta - Spirochaeta is a genus of spiral-shaped bacteria, but it does not fit the description of having 12-14 coils and pointed ends as mentioned in the question.

Correct Answer: B

Rationale: The correct answer is B: Clostridium tetani. Clostridium tetani produces tetanospasmin, a neurotoxin causing tetanus. It enters the body through wounds and affects the nervous system. A: Clostridium botulinum produces botulinum toxin causing botulism, not tetanus. C: Streptococcus pneumoniae causes pneumonia, not tetanus. D: Mycobacterium tuberculosis causes tuberculosis, not tetanus.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This is because Entamoeba histolytica is known to cause amebic dysentery, leading to chronic diarrhea. The presence of cysts with four nuclei in the stool sample is characteristic of Entamoeba histolytica. Giardia lamblia (choice B) is known to cause diarrhea but does not present with cysts containing four nuclei. Balantidium coli (choice C) is a ciliated protozoan that can cause diarrhea, but it does not have cysts with four nuclei. Trichomonas hominis (choice D) is a non-pathogenic protozoan commonly found in the human colon and is not associated with causing chronic diarrhea or cysts with four nuclei.

Correct Answer: B

Rationale: The correct answer is B because antigenic drift is not caused by the exchange of genetic information between animal and human influenza viruses. Antigenic drift is actually due to point mutations in the genes that encode for the surface proteins of the virus, leading to small changes in the antigens. These mutations can affect the hemagglutinin of both type A and B influenza viruses, making choices A and C correct. Choice D is incorrect because antigenic drift can occur in both type A and B influenza viruses, with type B being less prone to drift compared to type A.

Correct Answer: B

Rationale: The correct answer is B: Blood agar. Pneumococci are fastidious bacteria that require enriched media for cultivation. Blood agar provides essential nutrients and growth factors needed for the growth of pneumococci. It contains sheep blood, which provides hemin and NAD, supporting the growth of these bacteria. Kligler iron agar (A) is used for differentiating enteric bacteria based on glucose and lactose fermentation. Apocholate citrate agar (C) is used for the selective isolation of Escherichia coli. Peptone water (D) is a non-selective medium used for the initial cultivation of microorganisms.

Correct Answer: A

Rationale: The correct answer is A: prions. Prions are misfolded proteins that can cause spongiform encephalopathy by inducing normal proteins to misfold as well. Prions lack genetic material, distinguishing them from viruses (B), bacteria (C), and fungi (D), which all contain genetic material and cannot directly cause spongiform encephalopathy through protein misfolding.

Correct Answer: B

Rationale: The correct answer is B because anaerobic bacteria can grow in environments without oxygen. Anaerobic bacteria do not require oxygen for their metabolism and energy production. They can thrive in oxygen-deprived conditions by using alternative electron acceptors. Choice A is incorrect because anaerobic bacteria do not require oxygen to survive. Choice C is incorrect because anaerobic bacteria typically cannot survive in the presence of high concentrations of oxygen. Choice D is incorrect because anaerobic bacteria do not perform photosynthesis.