The technique used to study the internal structures of cells using electron beams is: MCQ with Answer and Explanation

Explanation:
Meristem culture, a type of tissue culture, involves excising the virus-free apical meristem (shoot tip) and growing it on a nutrient medium to produce a whole plant free of viruses. This is because meristematic cells lack vascular connections through which viruses spread. Cloning produces identical copies, hybridization crosses varieties, mutagenesis uses mutagens.

Explanation:
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:
Fossils are the preserved remains or traces of ancient organisms, providing crucial evidence for evolution. Analogous organs (like wings of birds and insects) perform similar functions but have different structural plans and evolutionary origins, indicating convergent evolution. Jean-Baptiste Lamarck proposed the theory of inheritance of acquired characters, while Charles Darwin proposed natural selection. Thus, statements 1 and 2 are correct.