In a double-stranded DNA, adenine pairs with thymine by how many hydrogen bonds?
A. One
B. Two
C. Three
D. Four
Answer: Option B
Solution (By JKExamLibrary)
Adenine (A) pairs with thymine (T) via two hydrogen bonds. Guanine (G) pairs with cytosine (C) via three hydrogen bonds. This base pairing (complementarity) is key to the double helix structure and ensures accurate replication and transcription. The higher number of bonds between G-C contributes to DNA stability; GC-rich regions are harder to denature.
Explanation:
O negative lacks A, B, and Rh antigens, so it can be given to anyone (RBCs). AB is universal recipient. Rh-negative lacks Rh antigen. Plasma is 90% water.
Explanation:
Angiogenesis is the growth of new blood vessels from pre-existing ones, important in development, wound healing, and tumor growth. Vasodilation is widening, vasoconstriction narrowing of vessels. Hematopoiesis is blood cell formation. Inhibiting angiogenesis is a cancer therapy strategy.
Explanation:
Niacin is part of NAD⁺/NADH, which donates electrons to the electron transport chain to generate the proton gradient for ATP synthesis. All B vitamins contribute indirectly.
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