Dna History and Structure

DNA History and Structure

From the beginning of time, it was questioned how traits were inherited. The study of DNA dates as far back as thousands of years ago. It wasn’t until the last 150 years when information about DNA began to advance and become more detailed. Thanks to the evolution of modern technology and better knowledge about the molecular world, we now know more about DNA and how traits are passed down from generation to generation. There have been many contributions to the knowledge of DNA and its structure. Gregor Mendel, Frederick Griffith, Oswald Avery, Erwin Chargaff , Rosalind Franklin, James Watson, and Francis Crick are a few known contributors to the world of molecular biology.

One of the earliest known contributors to DNA is Gregor Mendel. Gregor Mendel is known as the father of genetics because he demonstrated that the inheritance of certain traits in pea plants followed particular patterns. Mendel bred and crossbred thousands of plants and observed the characteristics of each generation. Mendel concluded that plant traits are handed down through hereditary elements in the sex cells (egg and sperm). These elements are now called genes today. He discovered that each plant receives a pair of genes for each trait, one gene from each of its parents.

Based on his experiments, he also concluded that if a plant inherits two different genes for a trait, one gene will be dominant and the other will be recessive. The trait of the dominant gene will appear in the plant while the recessive gene will be not be visible but still present. Mendel also concluded that the pairs of genes segregate randomly when a plant's sex cells are formed. This means that a parent plant hands down only one gene of each pair to its offspring.

After Mendel’s experiment, it was discovered that traits were passed down to the next generation and inherited as genes. But it was unclear where the genes were located. It wasn’t until 1928 when Frederick Griffith performed an experiment using mice and two types of bacteria, harmful and non harmful. He discovered that harmful bacteria can pass down characteristics to non harmful bacteria through an inheritance molecule. He called this process transformation. I wasn’t until another fourteen years later it was discovered what this inheritance molecule was. Oswald Avery performed an experiment where he destroyed the lipids, ribonucleic acids, carbohydrates, and proteins of the harmful bacteria but noticed transformation still happened. Next he destroyed the deoxyribonucleic acid and transformation did not occur. He then concluded that the inheritance molecule was DNA.

In 1950, Erwin Chargaff took samples of DNA from different cells and discovered that the amounts of adenine and thymine were about the same, and the amounts of guanine and cytosine were about the same also. In 1951, Rosalind Franklin was able to crystallize DNA and take an x-ray