DNA molecules contain information for building specific proteins. In a three-dimensional view, a DNA molecule looks like a spiral staircase; this is correctly called a helix. The constant parts of DNA molecules are the phosphate molecules, forming the DNA-ladder uprights or backbones. The information of DNA is actually coded in the sequence of nitrogen-containing bases, which are bound together to form the “rungs” of the DNA ladder. When the four DNA bases are combined in different three-base sequences called triplets, different amino acids of the protein are called for. It is said that the N-containing bases of DNA are complementary, which means that only certain bases can fit together or interact together. Specifically, this means that thymine can only bind with adenine, and cytosine can only bind with guanine.
The Correct Answer and Explanation is:
Correct Answer:
The DNA molecule is shaped like a helix. Its backbone is made of phosphate molecules, and the rungs of the ladder are formed by nitrogen-containing bases. These bases pair in a specific way: adenine pairs with thymine, and cytosine pairs with guanine. This base-pairing is referred to as complementary base pairing. DNA stores genetic information using sequences of these bases. When read in three-base units called triplets, these sequences code for different amino acids, which are the building blocks of proteins.
Explanation:
Deoxyribonucleic acid, or DNA, is the molecule that carries genetic instructions in living organisms. Structurally, it resembles a spiral staircase, which scientists refer to as a double helix. The sides of this twisted ladder, or its “backbones,” are formed by alternating sugar and phosphate molecules. These parts are consistent throughout the DNA strand and do not change from one section to another.
What carries genetic information are the nitrogen-containing bases, which form the steps, or “rungs,” of the ladder. There are four different DNA bases: adenine (A), thymine (T), cytosine (C), and guanine (G). These bases pair in a highly specific manner. Adenine always pairs with thymine, and cytosine always pairs with guanine. This pairing is due to the molecular shapes and chemical properties of the bases, allowing them to fit together like puzzle pieces.
This base-pairing is known as complementary base pairing, meaning that each base has only one correct partner. This rule ensures that DNA can be copied precisely during cell division, as each strand serves as a template for creating a new complementary strand.
The genetic code is read in groups of three bases at a time, known as triplets or codons. Each triplet corresponds to a specific amino acid, which is a building block of proteins. The sequence of triplets determines the sequence of amino acids, ultimately forming proteins that carry out various functions in the body. Thus, DNA provides the complete instructions for building proteins through its structure and base sequence.
