……… Let me introduce myself…………. Watson and Crick’s double helix model of DNA
(b. April 6, 1928, Chicago, Ill., U.S.), American geneticist and biophysicist who played a crucial role in the discovery of the molecular structure of deoxyribonucleic acid (DNA), the substance that is the basis of heredity.
In my turn……… Francis H.C. Crick (b. June 8, 1916,Northampton, Northamptonshire, Eng.), British biophysicist,who,with James Watson.During World War II, Crick interrupted his education to work as a physicist,but afterward he turned to biology at the Strangeways.
Then I will describe watson’s and my DNA model………….
The DNA model contains the actual metal plates used by James Watson and Francis Crick to determine the molecular structure of DNA in 1953. Constructed out of metal plates and rods arranged helically around a retort stand, the model shows one complete turn of the famous double helix. The metal plates represent the four bases whose complementary arrangement immediately suggested a possible copying mechanism for the genetic material.
…….. Let’s talk about our discovery of DNA Drs. Watson and Crick & The Discovery of DNA's Double Helix In 1954, Dr James Watson and Dr Francis Crick identified the structure of DNA, the cellular material that carries genetic codes. They found that DNA is made up of two protein strands connected by a phosphate backbone, forming what they termed the "double helix." Watson and Crick's discovery of the double helix laid the foundation for the study of genetics and the development of biotechnology.
What are DNA and Chromosomes……Crick?? it’s easy for me to explain these,watson,first………
DNA DeoxyriboNucleic Acid is commonly known as DNA. Originally discovered by Francis Crick and James Watson, the shape of DNA is a double helix. The composition of DNA is a series of nitrogenous bases and sugar and phosphate strands. Within the ladder model of DNA, the sugar and phosphate strands compose the sides of the DNA model, or molecule, while the actual rungs of the ladder are made up of the 4 nitrogen bases.
Chromosomes Chromosomes are the package for DNA and genes. To contain the DNA within the nucleus of a cell, the genetic information is wound up into strands like coiled rope. These strands take the shape of X's. The genetic information a chromosome holds, or one piece of genetic information a chromosome can hold, is known as a gene.
The order of gene code Primarily, it had to be understood that four nucleotide bases existed: adenine (A), guanine (G), cytosine (C), and thiamine (T) .By using Chargaff’s research, restrictions were established about the nucleotide sequencing and it was proven that A—T, T—A, C—G, and G—C were the only bonds. The pairing of the bases in this fashion was advantageous as Watson and Crick noted the pairs all measured a uniform width and could all easily fit into the frame of the double helix.
Yeah!!!!!!!!In the final,there are four things I must add and you need to understand…..
Figure 1: Portion of polynucleotide chain of deoxyribonucleic acid (DNA). The inset shows the corresponding pentose sugar and pyrimidine base in ribonucleic acid(RNA).
Figure 2: The bases of one helical strand in DNA are paired with complementary bases of the other strand by hydrogen bonds: adenine (A) is paired with thymine (T) and cytosine (C) is paired with guanine (G).
Figure 3: A possible method for the replication of DNA according to Watson and Crick. The arrows indicate the direction of rotation.
Figure 4:DNA base’s molecular structure is a small amount of negative electrical charge on nitrogen and oxygen atoms that are not attached to a hydrogen atom, a positive charge exists on those atoms that are attached to hydrogen.Adenine has surplus negative charge, thiamine has surplus positive charge.
bye This is the end of our presentation,bye