Problem 5 - Biology: Concepts and Applications

Question

What are the base-pairing rules for DNA? a. \(A-G, T-C\) b. \(A-C, T-G\) c. \(A-U, C-G\) d. \(A-T, G-C\)

Step-by-Step Solution

Answer

The correct base-pairing rule is option d: A-T, G-C.

Step 1: Identifying DNA Components

DNA is composed of four nucleotide bases, which are adenine (A), thymine (T), cytosine (C), and guanine (G). These bases form complementary pairs through hydrogen bonding.

Step 2: Understanding Base-Pairing Rules

The base-pairing rules in DNA are determined by the structures of the nucleotide bases. Adenine (A) pairs with thymine (T) through two hydrogen bonds, and cytosine (C) pairs with guanine (G) through three hydrogen bonds.

Step 3: Evaluating Options

Review the given options to identify which one correctly reflects the base-pairing rules of DNA. Based on our understanding, we are looking for A-T and C-G pairs.

Step 4: Selecting the Correct Answer

Option d indicates the base pairing of A-T and G-C, which matches our established understanding of DNA base pairing.

Key Concepts

Nucleotide Bases

Nucleotide bases are the building blocks of DNA, a vital molecule carrying genetic instructions necessary for the growth, development, functioning, and reproduction of all living organisms. There are four main nucleotide bases in DNA:

• Adenine (A)
• Thymine (T)
• Cytosine (C)
• Guanine (G)

These bases are paired with each other in a specific manner, helping to form the double helix structure of DNA. By understanding these bases, we can appreciate how genetic information is stored and transmitted across generations. Each base is a part of a nucleotide, which also includes a sugar molecule and a phosphate group. Together, these components form the backbone of the DNA strand.

Hydrogen Bonding

Hydrogen bonding plays a critical role in the structure of DNA. It is a type of weak attraction between a hydrogen atom and an electronegative atom, such as nitrogen or oxygen, in another molecule. In DNA, hydrogen bonds create connections between nucleotide bases on opposite strands, forming base pairs and stabilizing the DNA double helix.

• Adenine (A) and Thymine (T) form two hydrogen bonds
• Cytosine (C) and Guanine (G) form three hydrogen bonds

These bonds are strong enough to keep the DNA strands together but are weak enough to allow them to separate for replication and transcription, essential processes for cell division and protein synthesis. Without hydrogen bonding, the DNA double helix could not maintain its structure, leading to a loss of genetic information encoding.

Complementary Pairs

In DNA, complementary pairs refer to the specific pairing of nucleotide bases across the two strands of the DNA double helix. This concept of base pairing is pivotal for the accuracy of DNA replication and transcription. The rules for complementary pairing are:

• Adenine (A) always pairs with Thymine (T)
• Cytosine (C) always pairs with Guanine (G)

These pairings are guided by the chemical structures of the bases and the number of hydrogen bonds they can form, ensuring that each base on one DNA strand has a matching partner on the complementary strand. This complementary nature is crucial during cell division, allowing each new cell to receive an exact copy of the genetic material. By adhering to these rules, organisms ensure stability in their genetic sequences, which is fundamental for the transfer of traits from one generation to the next.