High School Biology : RNA Structure

Study concepts, example questions & explanations for High School Biology

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Example Questions

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Example Question #1 : Rna Structure

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

Possible Answers:

The sugar in DNA has a hydroxyl on the 2' carbon, while RNA 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 RNA has a hydroxyl on the 3' carbon, while DNA 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 #1 : Rna Structure

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:

ribose structure

uracil

hydrogen bonds

phosphodiester bonds

peptide 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 #1 : Rna Structure

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

Possible Answers:

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

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

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

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

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.

Example Question #2 : Rna Structure

How are RNA and DNA similar?

Possible Answers:

They both use the exact same bases

They both have a deoxygenated 2' carbon

They are both double stranded

They both have nucleotides linked by phosphodiester bonds

Correct answer:

They both have nucleotides linked by phosphodiester bonds

Explanation:

Although RNA and DNA have some key differences that result in different functions, they also have some key similarities. Both are composed of nucleotide monomers linked together by phosphodiester bonds. They are also both read in the 5'-3' direction. It is important to know that the backbone of both DNA and RNA is made by phosphodiester bonds, but it is hydrogen bonds that bind two strands to DNA together to form the double-helix.

DNA and RNA both use adenine, cytosine, and guanine, but only DNA uses thymine and only RNA uses uracil. Only DNA is double-stranded; RNA is single-stranded. Deoxyribose, in DNA, is deoxygenated at the 2' carbon, but ribose in RNA is oxygenated.

Example Question #2 : Rna Structure

Which of the following bases is replaced by uracil during transcription?

Possible Answers:

Cytosine

None of these

Adenine

Thymine

Guanine

Correct answer:

Thymine

Explanation:

DNA uses four nitrogenous bases: adenine, thymine, cytosine, and guanine. Adenine residues bond to thymine residues, and cytosine binds to guanine.

During transcription, DNA is used as a template to generate mRNA. During this process, bases are matched to the DNA template and used to build a single strand of RNA. In RNA, there are also four nitrogenous bases: adenine, cytosine, guanine, and uracil. Thymine is not found in RNA.

Example Question #2 : Rna Structure

Which nucleotide is present in RNA sequences, but not DNA sequences?

Possible Answers:

Thymine

Uracil

Guanine

Adenine

Correct answer:

Uracil

Explanation:

DNA sequences contain the following nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G). Guanine and cytosine bases pair together, while adenine and thymine bases pair together. In RNA, thymine is replaced by uracil (U).

Example Question #1 : Rna Structure

The following RNA sequence is reverse transcribed to generate cDNA (complementary DNA). What is the corresponding DNA sequence?

3'-AUCGGAUGCACA-5'

Possible Answers:

5'-TAGCCTACGTGT-3'

5'-UAGCCUACGUGU-3'

5'-AUCGGAUGCACA-3'

5'-ATCGGATGCACA-3'

Correct answer:

5'-TAGCCTACGTGT-3'

Explanation:

cDNA (and all DNA) sequences contain thymine (T) rather than uracil (U), which will form base pairs with adenine. Additionally, complementary DNA contains the "complement" of each RNA nucleotide. The resultant DNA will be oriented anti-parallel to the template RNA, and use complementary pairs of adenine-to-thymine and cytosine-to-guanine.

RNA: 3'-AUCGGAUGCACA-5'

DNA: 5'-TAGCCTACGTGT-3'

Example Question #1 : Understanding Differences With Dna

Where is mature mRNA found in the cell?

Possible Answers:

In the nucleus

In the mitochondria

In the cytoplasm or in the endoplasmic reticulum

In vesicles that are exocytosed by the cell

In the nucleolus 

Correct answer:

In the cytoplasm or in the endoplasmic reticulum

Explanation:

RNA goes through modifications known as "post-transcriptional modification" before it becomes a mature mRNA molecule. By the time that it is mature, it is allowed to leave the nucleus to interact with the ribosomes for translation. Ribosomes are free-floating in the cytoplasm of a cell and also on the rough endoplasmic reticulum. These are the targets of the mature mRNA.

The nucleus contains heteronuclear RNA (htRNA) before it becomes mature mRNA. The nucleolus accepts rRNA and helps form ribosomes subunits.

Example Question #9 : Rna Structure

There are several different types of RNA with different general structures and functions. What is common to all RNA molecules?

Possible Answers:

A hairpin loop

A globular structure

Thymine

Nitrogenous bases

Correct answer:

Nitrogenous bases

Explanation:

Each type of RNA is designed to complete a different function in the cell. Messenger RNA (mRNA) has a linear structure and provides the codon template for translation. Transfer RNA (tRNA) has a hairpin loop structure and carries amino acid residues to ribosomes for elongation of the polypeptide created from translation. Ribosomal RNA (rRNA) has a globular structure and forms an integral component of the ribosome subunits.

Despite their differences, all RNA molecules have the same backbone structure, which contains ribose sugars and phosphate groups, and the same nitrogenous bases: adenine, cytosine, guanine, and uracil.

Example Question #1 : Understanding Differences With Dna

How does RNA differ from DNA in eukaryotes?

I. RNA contains ribose 
II. RNA is found only in the cytoplasm
III. RNA uses bases A, C, U, G
IV. RNA is predominantly single-stranded 

Possible Answers:

I, III, and IV

I, II, III, and IV

I and III

I and IV

I and III

Correct answer:

I, III, and IV

Explanation:

RNA differs from DNA in that it contains a ribose instead of deoxyribose, uses uracil instead of thymine, and is not only found in the nucleus like DNA. In eukaryotes, RNA is transcribed in the nucleus, then it is exported into the cytoplasm where it binds to ribosomes during translation. RNA is indeed predominantly single-stranded.

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