Correct Option: B Explanation of Why Option B is Correct DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known living organisms and many viruses. The role of DNA in the transmission of characteristics is primarily through its ability to code for proteins, which are essential for the expression of traits.

1. Synthesis of RNA: The first step in the process of gene expression is transcription, where a specific segment of DNA is copied into messenger RNA (mRNA). This process occurs in the nucleus of eukaryotic cells. The mRNA serves as a template that carries the genetic information from the DNA to the ribosomes, the sites of protein synthesis.
2. Translation into Proteins: Once the mRNA reaches the ribosome, it undergoes translation. During this process, the sequence of nucleotides in the mRNA is read in sets of three (codons), and each codon corresponds to a specific amino acid. Transfer RNA (tRNA) molecules bring the appropriate amino acids to the ribosome, where they are linked together to form a polypeptide chain, which then folds into a functional protein.
3. Expression of Traits: The proteins produced as a result of this process play crucial roles in determining the physical and biochemical traits of an organism. For example, enzymes, hormones, and structural proteins are all products of gene expression that contribute to an organism's characteristics.

Why the Other Options are Incorrect A. DNA serves as the primary energy source for cellular functions. - This statement is incorrect because DNA does not provide energy. Instead, energy for cellular functions primarily comes from molecules like ATP (adenosine triphosphate). DNA's role is to store and transmit genetic information, not to serve as an energy source. C. DNA acts only as a structural component of the cell membrane. - This option is misleading. DNA is not a structural component of the cell membrane. The cell membrane is primarily composed of phospholipids and proteins. While DNA is found in the nucleus (in eukaryotes) and is crucial for genetic information, it does not play a direct role in the structure of the cell membrane. D. DNA is involved exclusively in cellular respiration processes. - This statement is incorrect because DNA is not exclusively involved in cellular respiration. Cellular respiration is the process by which cells convert glucose and oxygen into energy (ATP), and while some genes may code for enzymes involved in this process, DNA's primary role is in the storage and transmission of genetic information, not limited to respiration. Summary of Key Points

• DNA is essential for the synthesis of RNA, which carries genetic information from DNA to ribosomes.
• Proteins are synthesized from mRNA, and these proteins are responsible for the expression of traits in organisms.
• DNA does not serve as an energy source or a structural component of cell membranes, nor is it limited to cellular respiration.
• Understanding the role of DNA in protein synthesis is crucial for grasping how traits are transmitted in organisms.