DNA

Definition

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. It serves as the blueprint for life, containing the information necessary to produce proteins that perform a wide array of functions in the cell. The structure of DNA is a double helix, which is crucial for its ability to replicate and transmit genetic information across generations.

5 Must Know Facts For Your Next Test

1. DNA is composed of two strands that wind around each other to form a double helix, with each strand made up of nucleotides linked by phosphodiester bonds.
2. The four nitrogenous bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G). A pairs with T and C pairs with G, which is essential for accurate DNA replication.
3. DNA replication occurs during the S phase of the cell cycle and is semi-conservative, meaning each new double helix consists of one old strand and one new strand.
4. Mutations in DNA can lead to changes in protein structure and function, potentially resulting in various diseases or traits being expressed in an organism.
5. DNA transcription produces messenger RNA (mRNA), which carries the genetic information from the DNA in the nucleus to ribosomes in the cytoplasm for protein synthesis.

Review Questions

• How does the structure of DNA facilitate its function in genetic information storage?
  • The double helix structure of DNA allows it to efficiently store vast amounts of genetic information within a compact space. The specific pairing of nitrogenous bases (A with T and C with G) enables accurate replication during cell division, ensuring that genetic information is preserved. Additionally, the complementary nature of the strands allows for repair mechanisms to correct any errors that may occur during replication or as a result of damage.
• Discuss how mutations in DNA can impact gene expression and protein function.
  • Mutations in DNA can alter the sequence of nucleotides within a gene, which may lead to changes in the corresponding mRNA transcript during transcription. These changes can affect how proteins are synthesized, potentially leading to nonfunctional or malfunctioning proteins. Depending on their nature—such as missense mutations that change one amino acid or frameshift mutations that disrupt the reading frame—mutations can have varying effects on an organism's traits or health.
• Evaluate the significance of DNA replication and transcription in maintaining cellular functions across generations.
  • DNA replication is critical for cell division, allowing genetic material to be passed from one generation of cells to another. This process ensures that all daughter cells receive an identical copy of the parent cell's genetic information. Similarly, transcription transforms DNA into mRNA, which serves as a template for protein synthesis. This transition from genetic code to functional proteins is essential for carrying out cellular processes. Any errors in these processes can lead to dysfunctions and diseases, highlighting their importance in maintaining life.

Related terms

RNA:

RNA, or ribonucleic acid, is a molecule that plays several roles in the coding, decoding, regulation, and expression of genes. It is crucial in translating the genetic information carried by DNA into proteins.

Nucleotide: Nucleotides are the building blocks of DNA and RNA, consisting of a sugar, a phosphate group, and a nitrogenous base. The sequence of nucleotides in DNA encodes genetic information.

Gene: A gene is a segment of DNA that contains the instructions for making a specific protein or set of proteins. Genes are the functional units of heredity and influence traits in organisms.