GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Nucleic Acids

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

varsity tutors app store varsity tutors android store

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept

Example Questions

Example Question #1 : Help With Nucleic Acids

Which of the following nucleotides is present in RNA, but not DNA?

Possible Answers:

Guanine

Cytosine

Adenine

Uracil

Correct answer:

Uracil

Explanation:

Uracil is one of the nucleotide bases that composes RNA. It is replaced by thymine in DNA.

Uracil, thymine, and cytosine are pyrimidine residues, capable of bonding and pairing with the purines adenine and guanine via hydrogen bonding. During DNA replication, thymine matches with adenine. During transcription, uracil matches with adenine.

Example Question #2 : Help With Nucleic Acids

In DNA, which of the following nucleotides forms hydrogen bonds with guanine?

Possible Answers:

Uracil

Adenine

Thymine

Cytosine

Correct answer:

Cytosine

Explanation:

Nucleotides (DNA monomers) and ribonucleotides (RNA monomers) are formed from a pentose sugar, phosphate group, and nitrogenous base. Each nitrogenous base has a complement that allows it to form hydrogen bonds to the template strand. This allows for the proper sequence of genetic code in DNA replication and RNA transcription.

Purine residues will always pair with pyrimidine residues. The purines are adenine and guanine. The pyrimidines are cytosine and thymine in DNA, and cytosine and uracil in RNA. Adenine will match with thymine or uracil, forming two hydrogen bonds, while cytosine will match with guanine to form three hydrogen bonds.

Example Question #3 : Help With Nucleic Acids

Which of the following processes allows DNA mismatch repair enzymes to distinguish between old and new DNA strands?

Possible Answers:

Euchromatin

Methylation

Heterochromatin

Histone acetylation

Correct answer:

Methylation

Explanation:

Template strand cytosine and adenine are methylated in DNA replication, which allows DNA mismatch repair enzymes to distinguish between old and new DNA strands.

In contrast, histone acetylation relaxes DNA coiling and allows for the DNA to be transcribed.

You can remember that methylation makes DNA mute, and acetylation makes DNA active.

Example Question #4 : Help With Nucleic Acids

Which of the following amino acids is NOT necessary for purine synthesis?

Possible Answers:

Glutamine

Tyrosine

Aspartate

Glycine

Correct answer:

Tyrosine

Explanation:

Purines are defined by their two-ring structure. A six-member ring with two amine groups and a five-member ring with two amino groups join to form each purine molecule. Addition substituents on the rings (often ketones or other amines) determine purine identity.

Glycine, aspartate, and glutamine are necessary for purine synthesis, along with phosphoribosyl pyrophosphate (PRPP). Glycine is incorporated into the final purine product structure, while glutamine is converted to glutamate and aspartate is converted to fumarate. The final purine product is used to make useful molecules, such as adenine and guanine for nucleotide synthesis.

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept
Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: