Purine Bases in Nucleic Acids Quiz

Which of the following is NOT a pyrimidine base?

• Adenine

• Thymine

• Cytosine

• Uracil

Compare the structures of thymine and uracil. What is the main structural difference between them?

• Thymine has a methyl group that uracil lacks.

• Uracil has a methyl group that thymine lacks.

• Thymine has an extra amino group.

• Uracil has an extra phosphate group.

Which pyrimidine base contains an amino group attached to the ring?

• Cytosine

• Thymine

• Uracil

• Adenine

Which of the following are the correct complementary base pairs in DNA?

• Adenine–Thymine and Guanine–Cytosine

• Adenine–Cytosine and Guanine–Thymine

• Adenine–Guanine and Thymine–Cytosine

• Thymine–Cytosine and Adenine–Guanine

How many hydrogen bonds are formed between guanine and cytosine in DNA?

• 3

• 2

• 1

• 4

Which base does adenine pair with in RNA, and how many hydrogen bonds are formed between them?

• Uracil, 2 hydrogen bonds

• Thymine, 3 hydrogen bonds

• Cytosine, 2 hydrogen bonds

• Guanine, 3 hydrogen bonds

Which bonds are broken by DNA helicase during semiconservative replication?

• Hydrogen bonds between base pairs

• Covalent bonds in the sugar-phosphate backbone

• Peptide bonds between amino acids

• Ionic bonds between nucleotides

How is a new strand formed during semiconservative replication?

• Each original DNA strand serves as a template for a new strand.

• Both original DNA strands are discarded and two new strands are synthesized from scratch.

• Only one strand of the original DNA is used to make two new strands.

• The original DNA molecule remains unchanged and a completely new double helix is formed.

Which enzyme is responsible for joining adjacent nucleotides on the new DNA strand during semiconservative replication?

• DNA ligase

• DNA polymerase

• RNA polymerase

• Helicase

Explain why condensation reactions are important during the formation of a new DNA strand in semiconservative replication.

• They break down nucleotides.

• They form phosphodiester bonds between nucleotides.

• They separate the DNA strands.

• They unwind the DNA helix.