Genetic Foundations-: Genetic Continuity Is Vested in Single DNA Molecules

DNA is a long, thin organic polymer, the rare molecule that is constructed on the atomic scale in one dimension (width) and the human scale in another (length: a molecule of DNA can be many centimeters long). A hu man sperm or egg, carrying the accumulated hereditary information of billions of years of evolution, transmits this inheritance in the form of DNA molecules, in which the linear sequence of covalently linked nucleotide sub units encodes the genetic message.

Usually when we describe the properties of a chemical species, we describe the average behavior of a very large number of identical molecules. While it is difficult to predict the behavior of any single molecule in a collection of, say, a picomole (about 6x10¹¹) of a compound, the average behavior of the molecules is predictable because so many molecules enter into the average. Cellular DNA is a remarkable exception. The DNA that is the entire genetic material of E. coli is a single molecule containing 4.64 million nucleotide pairs. That single molecule must be replicated perfectly in every detail if an E. coli cell is to give rise to identical progeny by cell division; there is no room for aver aging in this process! The same is true for all cells. A human sperm brings to the egg that it fertilizes just one molecule of DNA in each of its 23 different chromo somes, to combine with just one DNA molecule in each corresponding chromosome in the egg. The result of this union is very highly predictable: an embryo with all of its 35,000 genes, constructed of 3 billion nucleotide pairs, intact. An amazing chemical feat.

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مواضيع ذات صلة

Genetic Foundations-: The Structure of DNA Allows for Its Replication and Repair with Near-Perfect Fidelity

Genetic Foundations

Physical Foundations-: Metabolism Is Regulated to Achieve Balance and Economy

Physical Foundations-: Enzymes Promote Sequences of Chemical Reactions

Physical Foundations:- Keq and ΔG Are Measures of a Reaction’s Tendency to Proceed Spontaneously

Physical Foundations:- Energy Coupling Links Reactions in Biology

Physical Foundations:- Creating and Maintaining Order Requires Work and Energy

Physical Foundations:- The Flow of Electrons Provides Energy for Organisms

Physical Foundations:- Organisms Transform Energy and Matter from Their Surroundings

Chemical Foundations

Cellular Foundations

Nucleic acids exist in a double helix