Question

why would it be problematic if dna used uracil instead of thymine as one of its bases? * 1 point
○ uracil would cause dna to degrade too quickly in the nucleus
○ uracil would make dna less stable and more prone to mutations
○ uracil would make dna too flexible for long - term storage
○ uracil would prevent dna from forming a double helix structure

considering that mrna, trna, and rrna all have different functions, what does this specialization suggest about the evolution of life? * 1 point
○ rna likely evolved before dna and originally performed multiple cellular functions
○ dna and rna evolved simultaneously to share cellular responsibilities
○ rna evolved from dna to become more specialized for specific tasks
○ all nucleic acids evolved independently to perform different functions

if a cell could only produce one type of nucleic acid, which would be more essential for basic life functions and why? * 1 point
○ rna, because it can both store information and catalyze essential reactions
○ dna, because it is more stable and less likely to be damaged
○ dna, because it stores all genetic information needed for inheritance
○ rna, because it can move freely throughout the cell

Explanation:

First Question (Why would it be problematic if DNA used uracil instead of thymine as one of its bases?)

Thymine has a methyl group that uracil lacks. This methyl group in thymine provides extra stability to the DNA structure. Uracil is more prone to deamination (spontaneous loss of an amino group), which can lead to mismatches during replication and thus increase mutation rates. Let's analyze each option:

• "Uracil would cause DNA to degrade too quickly in the nucleus": Uracil doesn't cause rapid degradation in the nucleus; DNA degradation is due to other factors like nucleases, so this is incorrect.
• "Uracil would make DNA less stable and more prone to mutations": As explained, uracil's lack of the methyl group makes DNA less stable, and its deamination can lead to mutations. This is correct.
• "Uracil would make DNA too flexible for long - term storage": Uracil doesn't affect DNA's flexibility related to long - term storage in this way. The stability of the double - helix and base - pairing are more related to stability for storage, so this is incorrect.
• "Uracil would prevent DNA from forming a double helix structure": Uracil can still form base - pairs (with adenine) and DNA can still form a double helix. So this is incorrect.

The RNA world hypothesis suggests that early life had RNA performing multiple functions (catalytic, informational). As life evolved, different types of RNA (mRNA, tRNA, rRNA) became specialized for different tasks. Now let's analyze the options:

• "RNA likely evolved before DNA and originally performed multiple cellular functions": This is in line with the RNA world hypothesis. RNA could have been the first nucleic acid, performing functions like catalysis (ribozymes) and information storage, and later DNA evolved for more stable information storage, while RNA became specialized into different types (mRNA for carrying information, tRNA for transfer, rRNA for ribosomes).
• "DNA and RNA evolved simultaneously to share cellular responsibilities": There is no evidence for simultaneous evolution with this kind of sharing. The RNA world hypothesis points to RNA first. So this is incorrect.
• "RNA evolved from DNA to become more specialized for specific tasks": The evolutionary order is thought to be RNA first, then DNA. So this is incorrect.
• "All nucleic acids evolved independently to perform different functions": Nucleic acids (DNA and RNA) are related, with RNA likely being the precursor to DNA in terms of evolution. They did not evolve independently. So this is incorrect.

RNA has two key properties: it can store genetic information (like DNA) and it can act as a catalyst (ribozymes) for essential biochemical reactions. Let's analyze the options:

• "RNA, because it can both store information and catalyze essential reactions": This is correct. RNA's dual - function (informational and catalytic) makes it more essential for basic life functions if only one nucleic acid is present.
• "DNA, because it is more stable and less likely to be damaged": DNA is stable but it cannot catalyze reactions. For basic life functions, catalytic activity is also needed, so DNA alone would not be sufficient.
• "DNA, because it stores all genetic information needed for inheritance": Again, DNA lacks catalytic activity. Life needs more than just information storage; it needs reactions to occur, so this is incorrect.
• "RNA, because it can move freely throughout the cell": The ability to move freely is not the key reason for being essential for basic life functions. The key is its dual - function of information storage and catalysis. So this is incorrect.

Answer:

B. Uracil would make DNA less stable and more prone to mutations

Second Question (Considering that mRNA, tRNA, and rRNA all have different functions, what does this specialization suggest about the evolution of life?)