Double fertilization in angiosperms was discovered by: MCQ with Answer and Explanation

Explanation:
The skin and mucous membranes form the first line of defense (innate immunity), acting as physical barriers that prevent pathogens from entering the body. White blood cells (leukocytes), including phagocytes and lymphocytes, are the cellular components of the immune system that identify, attack, and destroy pathogens. Antibiotics are drugs designed to kill or inhibit the growth of bacteria; they are completely ineffective against viruses, which lack the cellular machinery targeted by antibiotics. Thus, statements 1 and 2 are correct.

Explanation:
Bt cotton contains cry genes from Bacillus thuringiensis, producing insecticidal proteins toxic to bollworms, reducing pesticide use.

Explanation:
Restriction endonucleases are molecular scissors that recognize and cut DNA at specific, highly specific palindromic nucleotide sequences, creating fragments with sticky or blunt ends. DNA ligase is an enzyme that catalyzes the formation of phosphodiester bonds between adjacent DNA fragments, effectively joining or 'pasting' them together, crucial in recombinant DNA technology. PCR (Polymerase Chain Reaction) is used to exponentially amplify specific DNA segments, not to sequence them; DNA sequencing is a separate technique. Thus, statements 1 and 2 are correct.