Assertion (A): Cuscuta is a parasitic plant. Reason (R): It has chlorophyll and can photosynthesize its own food. MCQ with Answer and Explanation

Explanation:
Restriction enzymes cut DNA at recognition sites, DNA ligase seals fragments, and PCR amplifies specific DNA sequences. All three are fundamental tools in biotechnology.

Explanation:
HIV is a retrovirus with two copies of single-stranded RNA as its genome. It uses reverse transcriptase to convert RNA into DNA upon infection. Double-stranded DNA is typical of many organisms. Single-stranded DNA viruses exist (e.g., parvovirus). Double-stranded RNA viruses include rotavirus. The viral RNA genome enables integration into host DNA via a DNA intermediate.

Explanation:
Vitamin A (retinal) combines with opsin to form rhodopsin in rod cells, necessary for vision in dim light. Deficiency causes night blindness. B₁ is for carbohydrate metabolism, C for collagen, D for calcium.