Test I. Multiple Choice. Choose only the letter.

The sugar in DNA is a deoxyribose. Which of the following is correct?

• The sugar lacks hydrogen atom in carbon

• The sugar lacks oxygen atom in carbon 2

• The sugar lacks hydrogen atom in carbon 5

• The sugar lacks oxygen atom in carbon 5

Answer explanation

The correct choice is that the sugar in DNA, deoxyribose, lacks an oxygen atom at carbon 2. This distinguishes it from ribose, which has an -OH group at that position, making deoxyribose a 'deoxy' sugar.

Which of the following is NOT a pyrimidine base?

• A. Adenine

• B. Cytosine

• C. Uracil

• D. Thymine

Answer explanation

Adenine is not a pyrimidine base; it is a purine. Pyrimidine bases include cytosine, uracil, and thymine. Therefore, the correct answer is A. Adenine.

Which statement is TRUE regarding DNA and RNA?

• DNA's sugar is ribose; RNA's sugar is deoxyribose.

• DNA is single stranded; RNA is double stranded.

• DNA contains thymine; RNA contains uracil.

• DNA is in cytoplasm; RNA is in nucleus.

Answer explanation

The correct statement is that DNA contains thymine, while RNA contains uracil. This distinguishes the two nucleic acids, as DNA uses thymine and RNA substitutes it with uracil.

A nucleotide is formed by the union of:

• Ribose sugar and base

• Nucleoside and phosphate group

• Nucleoside and pyrimidine base

• Nucleoside and purine base

Answer explanation

A nucleotide consists of a nucleoside (which is a sugar and a base) and a phosphate group. Therefore, the correct answer is 'Nucleoside and phosphate group', as it accurately describes the components of a nucleotide.

Which reagent of the homogenizing solution in DNA extraction that removes the lipid composition of the fruit?

• Dishwashing liquid

• Ethanol

• Sodium chloride

• Water

Answer explanation

Dishwashing liquid is effective in DNA extraction as it contains surfactants that break down cell membranes, including lipids, allowing the release of DNA. Ethanol is used later to precipitate DNA, not to remove lipids.

Part of DNA extraction in blending. What is disrupted in this part?

• Ribosome

• Cell wall

• Nucleus

• Mitochondria

Answer explanation

In DNA extraction, blending disrupts the cell wall, allowing access to the contents of the cell, including the nucleus where DNA is located. The other options, like ribosomes and mitochondria, are not directly disrupted in this process.

What is tested in Diphenylamine test?

• Deoxyribose

• Phosphate group

• Purine base

• Ribose

Answer explanation

The Diphenylamine test specifically detects deoxyribose, a sugar component of DNA. It reacts with deoxyribose to produce a blue color, confirming its presence, while not reacting with ribose or other components.

Ethanol added in the final step of DNA extraction separates the DNA product from the homogenate. Why?

• DNA is insoluble in ethanol thus it will precipitate out from the homogenate

• DNA is soluble in ethanol thus it will precipitate out from the homogenate

• DNA is soluble in salt thus it will precipitate out from ethanol

• None from the choices

Answer explanation

DNA is insoluble in ethanol, which causes it to precipitate out from the homogenate. This is a key step in DNA extraction, allowing for the separation of DNA from other cellular components.

Hydrolyzed means break down.

• Yes

• No

Answer explanation

Hydrolyzed refers to the process of breaking down substances, typically through the addition of water. Therefore, the statement that hydrolyzed means break down is correct. The answer is Yes.

The following are factors that helped in the acidic hydrolysis of DNA molecule in the experiment except:

• A. pH

• B. Heat

• C. Water

• D. Amount of reagent

Answer explanation

Water is a necessary component for hydrolysis but does not influence the acidity of the reaction. pH, heat, and the amount of reagent directly affect the hydrolysis process, making C the correct choice.