555

The EDTA works as a chelating agent in DNA extraction. It chelates the metal ions present in the enzymes, metal ions work as a cofactor to increase the catalytic activities of an enzyme. In DNA or RNA extraction, the use of EDTA readily deactivates DNase or RNase enzymes which digest DNA or RNA, respectively.

Stepwise Solution: Part (a): Are genes a and b linked? How do you know? Understanding the problem: If genes a and b are linked, they will not assort independently, and the number of parental ditypes (PD) will be significantly greater than the number of non-parental ditypes (NPD). Analyzing the data: From the table: Parental ditypes (PD) = Tetrads with only parental combinations (a⁺b and ab⁺) → Type I = 85. Non-parental ditypes (NPD) = Tetrads with only recombinant combinations (a⁺b⁺ and ab) → Type VI = 3. Tetratypes (T) = Tetrads with all four combinations → Types II, III, IV, V, VII, VIII = 2 + 3 + 2 + 3 + 1 + 1 = 12. Conclusion: Since PD ≠ NPD (PD is much greater), this suggests that genes a and b are linked