Question

the model below compares the typical structures of rna and dna. all possible nucleotides are shown.
rna strand
dna double helix
image with labels: nitrogenous bases (adenine, thymine, guanine, cytosine, uracil); ribose - phosphate backbone; deoxyribose - phosphate backbone; hydrogen bonds between base pairs
what are the main differences between rna and dna? select all that apply.

• rna contains the 5 - carbon sugar ribose instead of deoxyribose.
• rna contains weak hydrogen bonds between its phosphate groups and 5 - carbon sugars.
• dna is usually double - stranded, while rna is usually single - stranded.
• rna does not contain thymine. instead, it has a nitrogenous base called uracil.

Explanation:

1. Sugar Component: RNA has ribose (a 5 - carbon sugar) and DNA has deoxyribose (ribose with one less oxygen atom), so the first option is correct.
2. Strand Structure: DNA typically exists as a double - helix (double - stranded), and RNA is usually single - stranded, so the third option is correct.
3. Nitrogenous Bases: RNA uses uracil (U) instead of thymine (T) which is present in DNA, so the fourth option is correct.
4. Bond Type: The bonds between phosphate and sugar in nucleic acids are phosphodiester bonds (covalent), not hydrogen bonds, so the second option is incorrect.

Answer:

The correct options are:

• RNA contains the 5 - carbon sugar ribose instead of deoxyribose.
• DNA is usually double - stranded, while RNA is usually single - stranded.
• RNA does not contain thymine. Instead, it has a nitrogenous base called uracil.

The option "RNA contains weak hydrogen bonds between its phosphate groups and 5 - carbon sugars" is incorrect. In both RNA and DNA, the bonds between phosphate groups and 5 - carbon sugars are covalent (phosphodiester bonds), not hydrogen bonds.