High School Biology : Understanding RNA Backbone

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Understanding Rna Backbone

What is the difference in the structure of the sugars used in RNA and DNA?

Possible Answers:

The sugar in RNA has a hydroxyl on the 3' carbon, while DNA does not

The sugar in RNA has a hydroxyl group on the 2' carbon, while DNA does not

The sugar in DNA has a hydroxyl on the 3' carbon, while RNA does not

The sugar in DNA has a hydroxyl on the 2' carbon, while RNA does not

Correct answer:

The sugar in RNA has a hydroxyl group on the 2' carbon, while DNA does not

Explanation:

The full names of the sugars used in nucleic acid structures are ribose (for RNA) and deoxyribose (for DNA). Both sugars have five carbon atoms arranged in a ring. In ribose, the carbon in the 2' position is bound to a hydroxyl group (-OH). In deoxyribose, however, the 2' carbon is bound to a simple hydrogen atom. 

Example Question #2 : Understanding Rna Backbone

DNA and RNA have similar structures but some differences, and are used for different functions within the cell.

The backbone of RNA is different from the backbone of DNA due to the presence of __________.

Possible Answers:

peptide bonds

phosphodiester bonds

ribose structure

uracil

hydrogen bonds

Correct answer:

ribose structure

Explanation:

DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) have backbones that are identical, except that the five-carbon sugar in RNA (ribose) has one oxygen that the sugar in DNA (deoxyribose) lacks.

Hydrogen bonding is no different between the two molecules, and primarily serves to bind nitrogenous bases rather than regions of the backbone.

Peptide bonds are not formed in DNA or RNA. Rather, these bonds are used to connect the amino acid monomers in a protein molecule.

Uracil is found in RNA and not in DNA, but does not impact the backbone.

Phosphodiester bonds are used to bind adjacent nucleotides together in both DNA and RNA.

Example Question #3 : Understanding Rna Backbone

Which of the following is NOT true of RNA and DNA?

Possible Answers:

RNA has a single helix, while DNA has a double helix.

DNA codes for RNA, which in turn codes for proteins.

RNA has the base uracil and DNA has the base thymine.

RNA has the base thymine and DNA has the base uracil.

Correct answer:

RNA has the base thymine and DNA has the base uracil.

Explanation:

RNA differs from DNA in that it has a single helix, and that instead of thymine, it contains uracil.

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