Question

a scientist discovers that a particular nucleic acid molecule is highly stable, resistant to alkaline conditions, and contains thymine. based on these characteristics, what can the scientist conclude about this molecule’s primary function?
options:

• it acts as long - term storage for genetic information that must be preserved
• it works as an enzyme catalyst for metabolic reactions
• it serves as a temporary messenger carrying instructions for immediate use
• it functions as a structural component that needs frequent replacement

if rna contained deoxyribose sugar instead of ribose sugar, how would this structural change most likely affect its cellular function?
options:

• rna would become better at resisting uv radiation damage
• rna would be able to store more genetic information in its structure
• rna would become more stable but less able to move freely through the cell
• rna would become more flexible and better at forming temporary structures

why is the base pairing rule that purines always pair with pyrimidines essential for dna’s double helix structure?
options:

• it allows dna to store more information in a smaller space
• it ensures that the genetic code can be read in both directions
• it maintains consistent spacing and width throughout the dna molecule
• it prevents mutations from occurring during dna replication

Explanation:

First Question

1. Recall nucleic acid types: DNA has thymine, is stable, resistant to alkali. RNA has uracil, less stable.
2. Analyze options:

• Long - term genetic storage: DNA (with thymine, stable) does this. Enzymes (catalysts) are proteins/RNA (no thymine). Temporary messenger is RNA (uracil). Structural component with frequent replacement is not DNA's role.

1. Deoxyribose (in DNA) is more stable than ribose (in RNA). Ribose makes RNA flexible for temporary structures.
2. Analyze options:

• UV resistance: Sugar change not related to UV. Storing more info: Sugar doesn't increase info storage. More stable (deoxyribose) but less flexible (so less free movement) matches. More flexible: Deoxyribose is less flexible than ribose.

1. Purines (A, G) are double - ringed, pyrimidines (T, C) are single - ringed. Pairing them (A - T, G - C) keeps the DNA helix width consistent.
2. Analyze options:

• Storing more info: Base pairing rule not about info storage amount. Reading in both directions: Not related to base pairing type. Maintaining spacing: Correct, as purine - pyrimidine pairing keeps the helix width uniform. Preventing mutations: Base pairing rule doesn't prevent mutations (mutations are changes in sequence).

Answer:

A. It acts as long - term storage for genetic information that must be preserved

Second Question