Blotting techniques in molecular biology:

• Southern blot analyzes DNA fragments; Northern blot analyzes RNA molecules; Western blot detects specific proteins using antibodies.
• Eastern blotting is an extension of Western blotting designed to detect post-translational modifications (PTMs) of proteins, such as carbohydrate epitopes, glycosylation, phosphorylation, and lipidation, using probes like lectins, cholera toxin, or phosphospecific antibodies.
• Therefore, Eastern blot evaluates post-translational modifications in proteins.

Frequency of restriction endonuclease recognition sites:

• In random DNA with equal base distribution ($25\%$ each of A, T, G, C), a specific recognition sequence of length $n$ bases occurs on average once every $4^n$ base pairs.
• For a 5-base cutter ($n = 5$): $\text{Average distance} = 4^5 = 1024\text{ bp}$.
• For a genome of $6066\text{ bp}$, the number of cleavage sites is $\approx 6066 / 1024 \approx 5.92 \approx 6$ sites.
• Cleaving into fragments yields approximately 6 fragments for circular genomes or 7 for linear genomes, hence 'About 6' is the correct answer.

PCR scope and biological limitations:

• PCR amplifies cell-free naked DNA fragments in vitro.
• PCR products can be used for site-directed mutagenesis (using mutagenic primers), sex determination (amplifying Y-specific or sex-linked markers), and estimating recombination frequency (marker genotyping).
• In vitro regeneration of a complete multicellular organism requires living, totipotent cells/tissues containing intact epigenetic state, organelles, and cellular machinery (tissue culture/cloning), which cannot be achieved from isolated DNA fragments alone.

FlavrSavr tomato biotechnology:

• Calgene developed the Flavr Savr tomato (commercialized in 1994), which was the first genetically engineered commercial crop approved for human consumption.
• It used antisense RNA technology to suppress the expression of the endogenous polygalacturonase (PG) enzyme, which breaks down pectin in the cell wall during fruit ripening.
• Reduced PG expression drastically delayed fruit softening, allowing prolonged vine ripening and enhanced shelf-life.