Rucete ✏ Lehninger Principles of Biochemistry In a Nutshell
1.4 Genetic Foundations
This chapter explores the genetic basis of life, focusing on how cells faithfully transmit genetic information across generations and how DNA’s structure supports replication, repair, and the encoding of proteins.
Continuity of Genetic Information
• Living organisms can reproduce for countless generations with nearly perfect fidelity, maintaining genetic instructions almost unchanged over billions of years.
• The genetic material—DNA—retains its structure and composition, providing remarkable stability and continuity in living systems.
• DNA contains the encoded instructions necessary for an organism’s structure and function, with little change through evolutionary time.
The Molecular Nature of DNA
• DNA is a long, linear organic polymer, with a one-dimensional atomic structure and a length that spans human-scale dimensions.
• The sequence of covalently linked nucleotide subunits (deoxyribonucleotides) encodes all genetic information.
• In sexual reproduction, the precise union of DNA from sperm and egg produces a new individual with a predictable and intact genetic complement.
• Faithful DNA replication is essential; each cell division requires exact copying of the entire genome, without room for errors or “averaging.”
Structure and Replication of DNA
• DNA consists of two complementary polymeric strands twisted into a double helix.
• Each nucleotide in one strand pairs specifically with its complementary nucleotide in the other (A with T, G with C), held together by hydrogen bonds.
• Before cell division, the strands separate and serve as templates for synthesizing new complementary strands, ensuring each daughter cell receives an identical genome.
• The complementarity of DNA strands also allows for efficient repair when one strand is damaged.
From DNA Sequence to Protein Function
• The linear DNA sequence encodes proteins via a two-step process: transcription into RNA and translation into a linear chain of amino acids (the protein).
• The amino acid sequence dictates the protein’s three-dimensional structure, which is stabilized by noncovalent interactions and, in many cases, aided by molecular chaperones.
• The final, correctly folded conformation (native state) is crucial for protein function.
• Proper protein folding and assembly also depend on the cellular environment (pH, ions, etc.), not just the DNA sequence alone.
Self-Assembly and Supramolecular Complexes
• Proteins, nucleic acids, and lipids can associate noncovalently to form larger supramolecular complexes like chromosomes, ribosomes, and membranes.
• These complexes assemble spontaneously through specific, high-affinity interactions among individual macromolecules.
In a Nutshell
The genetic information of life is stored in the precise linear sequence of DNA, which is replicated and repaired with near-perfect fidelity. DNA encodes proteins, which fold into unique three-dimensional structures necessary for cellular function. Supramolecular assemblies arise from specific interactions among macromolecules. The stability and accuracy of genetic information across generations are the foundations of biological continuity.