Which of the following are not found in Cyanobacteria?

Correct Answer: C

Rationale: The correct answer is C: chloroplasts. Cyanobacteria do not have chloroplasts because they are prokaryotic organisms and do not possess membrane-bound organelles like chloroplasts found in eukaryotic cells. Instead, they perform photosynthesis using thylakoids, which are membrane-bound compartments where photosynthesis occurs. Gas vesicles are also present in cyanobacteria and help regulate their buoyancy. Heterocysts are specialized cells that aid in nitrogen fixation, a process that allows cyanobacteria to convert atmospheric nitrogen into a form that can be used by the organism. Therefore, the absence of chloroplasts in cyanobacteria makes choice C the correct answer.

Correct Answer: B

Rationale: The correct answer is B: carotenoids. Carotenoids are photosynthetic pigments that are found in all prokaryotic and eukaryotic photoautotrophs. They play a key role in capturing light energy for photosynthesis. Chlorophyll c, phycobilins, and phycocyanin are not found in all prokaryotic and eukaryotic photoautotrophs. Chlorophyll c is primarily found in certain algae, phycobilins are specific to cyanobacteria and red algae, and phycocyanin is a type of phycobilin found in cyanobacteria. Carotenoids are the only pigment that is universally present across all photoautotrophs.

Correct Answer: C

Rationale: The correct answer is C: Autoimmune diseases. This is because autoimmune diseases occur when the immune system mistakenly attacks the body's own tissues or organs. In this condition, the immune system fails to recognize self from non-self, leading to inflammation and tissue damage. A: Allergies involve an exaggerated immune response to harmless substances, not attacking self-tissues. B: Immunodeficiencies result in a weakened immune system, making it less effective at fighting infections, not attacking self-tissues. D: Delayed hypersensitivity is a type of immune response that occurs hours to days after exposure to an allergen, not involving the immune system attacking self-tissues. In summary, autoimmune diseases are characterized by the immune system targeting the body's own tissues or organs, distinguishing them from allergies, immunodeficiencies, and delayed hypersensitivity.

Correct Answer: C

Rationale: The correct answer is C: Smal. Smal is a restriction endonuclease that cuts DNA at specific sequences, producing fragments with blunt ends. Smal recognizes the sequence CCCGGG and cuts between the two C's on both strands, resulting in blunt-ended fragments. Explanation for incorrect choices: A: Sacl - Sacl produces sticky ends, not blunt ends. B: EcoRI - EcoRI produces sticky ends with overhangs. D: HindIII - HindIII also produces sticky ends with overhangs. In summary, Smal is the only enzyme among the choices that generates DNA fragments with blunt ends.

Correct Answer: C

Rationale: The correct answer is C: Terminal deoxynucleotidyl transferase (TdT). TdT catalyzes the addition of deoxynucleotides to the 3'OH ends of DNA molecules. It does so by adding nucleotides in a template-independent manner, making it crucial for generating diversity in immune cell receptor genes. A: Phosphohydrolase - This enzyme is not involved in adding deoxynucleotides to DNA ends. B: T4 DNA ligase - This enzyme catalyzes the joining of DNA fragments, not the addition of deoxynucleotides. D: DNA endonuclease - This enzyme cleaves DNA internally, not involved in adding deoxynucleotides to DNA ends.