In DNA, adenine forms ___________ hydrogen bonds with ____________.
a. Three / uracil
b. Two / uracil
c. Two / thymine
d. Three / thymine

Verified step by step guidance

1. Recall the base pairing rules in DNA, where adenine (A) pairs specifically with thymine (T), and guanine (G) pairs with cytosine (C).
2. Understand that adenine and thymine form hydrogen bonds to stabilize the DNA double helix structure.
3. Remember the number of hydrogen bonds between base pairs: adenine and thymine form two hydrogen bonds, while guanine and cytosine form three.
4. Note that uracil is found in RNA, not DNA, so it does not pair with adenine in DNA.
5. Combine these facts to conclude that adenine forms two hydrogen bonds with thymine in DNA.

Key Concepts

Base Pairing Rules in DNA

In DNA, nitrogenous bases pair specifically: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). This complementary base pairing is essential for DNA structure and replication.

Hydrogen Bonding Between Bases

Hydrogen bonds stabilize the DNA double helix by connecting complementary bases. Adenine and thymine form two hydrogen bonds, while cytosine and guanine form three, influencing DNA stability.

Difference Between DNA and RNA Bases

DNA contains thymine as a base, whereas RNA contains uracil instead of thymine. This distinction is important when identifying correct base pairing in DNA versus RNA molecules.