Two scientists, Max and Gunther, proposed a paper with three different methods of DNA replication. First they explained semi-conservative replication, which is a daughter strand that contains one strand from the parent and the other is newly formed. The second was conservative replication which theorized a new double helix strand being created in the first generation. Third they described dispersive DNA replication where both a new and old strand break and separate. It was known that DNA can be copied; but scientists could not understand which of these methods took place. Watson and Crick wrote an article about DNA replication and how it would separate forming two chains as semi-conservative replication. The two scientists, Matthew Meselson and Franklin Stahl, discussed a method to test this theory of semi-conservative replication.
DNA is a three dimensional structure that carries hereditary information, each strand has nucleotides containing a base, sugar, and phosphate. The four chemical bases always pair in the same way; adenine joins to thymine (A&T) and cytosine joins guanine (C&G). The Meselsen-Stahl experiment was based on reactions with heavy isotopes of nitrogen in order to identify the new and old DNA strand. Nitrogen’s atomic mass number is 14 which means that it contains 7 protons and 7 neutrons. Heavy isotopes have an extra neutron which makes it heavier and it’s called 15N.
In their experiment they grew E. coli (bacteria) on a medium containing heavy
Understanding DNA can take a lot of studying and confusion to even get the general idea of the concept. The structure of DNA is very complicated and complex to understand, but researchers James Watson, Francis Crick, Maurice Wilkins, and Rosalind Franklin all developed the idea of the DNA structure in 1953. Deoxyribonucleic Acid is found in the nucleus of the cell. It is a double stranded molecule that contains the genetic code and is the main component of chromosomes. DNA is the blueprint of organisms. Nucleotides are the basic unit of DNA and they are made up of sugar, phosphate, and one of the four basis including adenine,
In the early 1950s, the race to find the structure of DNA was in full swing. The search was being conducted at three different colleges. At the California Institute of Technology, Linus Pauling,
Over the course of the modern age, the human body was still a mystery waiting to be solved. The body contains secrets one can only hope to discover. Over the twentieth century, scientists tried to understand one of the most complex concepts in the biological field. DNA (Deoxyribonucleic acid) was at the forefront of research. Several theories claimed to have solved the structural concept of DNA. However, it was not until Francis Crick and James D. Watson discovered the true structure, the double helix. However, many potential models of DNA had passed through the biology field until eventual lose of credibility. The past models would contain a fixed detail that would make the entire concept invalid. In James D. Watson book, The Double Helix, he illustrates his path amid incorrect theories until he reaches the model that is taught around the world today.
When Pauling and Cory attempted to come up with the structure of DNA, they thought that the DNA helix was a triple helix. This was because they misinterpreted DNA A structure and concluded that the phosphate and sugars were on the inside and the nucleotide bases were on the outside. Watson and Crick said this was not possible because phosphates can’t fit together inside the helix without breaking their molecular bonds. The studies Watson and Crick made were based off of DNA B molecule from the X-ray of DNA B taken by Rosalind Franklin that had low concentration, rather than A DNA which was high in salt concentration that gave Pauling an improper representation of the DNA helix. Pauling and Cory stated that the helix was made of three helices, Watson and Crick disapproved of this concept because phosphate backbones are negatively charged, it was impossible to put three negatively charged strands with each
Chapter 1: Genes can be demonstrated as “instruction books for making functional markers such as ribonucleic acid(RNA) and proteins”(Chapter 1, page 4). Distinctively, the four nitrogenous bases to code the gene of DNA is adenine, thymine, guanine, and cytosine. In addition, Rosalind Franklin was among the primitive people to experiment with X rays as a form of molecular photography in order to learn more about DNA and its structure. The structure of DNA taught a constitutional fact about genetics; it stated that the two strands of DNA were complementary to each other. Moreover, DNA replicates in order to make new sets of
In Time Magazine an article states On February 28 1953, James Watson and Francis Crick broke the DNA code and discovered that the DNA strand is double helix and forms like a ladder. They found that cytosine and guanine were paired together and that adenine and thymine were paired. They discovered the building block of life (Wright, 1999). DNA is found in all living organisms.
Two scientists from Cambridge University named James Watson and Francis Crick were the first ones to actually build the actual structure of the DNA molecule. In building their DNA molecule, they discovered that there were two different types of bases, purines and pyrimidines. Purines were the larger of the two types of bases, and are the double ringed structures [example of nucleotides that fit in this category are adenine (A) and guanine (G)]. Pyrimidines were the smaller of the two types of bases, and are the only single ringed structures [example of nucleotides that fit in this category are cytosine (C) and thymine (T)]. The two scientists also discovered that in the DNA molecule, only two base pairings of nucleotides are possible, adenine (A) with guanine (G) and thymine (T) with cytosine (C). This is because of the improper forming of hydrogen bonds. In a G-C pairing, three hydrogen bonds are formed whereas in an A-T pairing, only two hydrogen bonds are formed.
Rosalind Franklin was able to take an x-ray image of the DNA strand and see how it was shaped. After seeing her work James Watson and Francis Crick took her image and began researching into it. This led them to discover the double helix.
DNA, Deoxyribonucleic Acid, is the basic structure for all life, it is the blueprint, the instruction manual, on how to build a living organism. DNA is made up of four nitrogen bases, adenine, thymine, cytosine, and guanine which are connected by sugar-phosphate bonds. Through a process called Protein Synthesis, the nitrogen bases are the code for the creation of amino acids. Essentially, DNA makes amino acids, amino acids make proteins, proteins make organisms. This process has been taking place for much longer than scientists have been able to document. Those scientists are called geneticists and their field is genetics.
The work of these four people led to a complete restructuring of the beliefs of the scientific community regarding genetic information. Their initial word led to further work which encompassed their hypothesis of how DNA replicates itself. From this work came the modern technologies of DNA fingerprinting and sequencing.
DNA replication is described as semi-conservative. It is semi-conservative because the replication of one helix results in two daughter helices each of which contains one of the original parental helical strands. Furthermore, it is semi-conservative because the two new daughter DNA molecules are “half old” and “half new”; this means that half the original DNA molecule is saved, or conserved in the daughter DNA molecules.
Crick and Watson used X-ray diffraction data, which Rosalind Franklin developed which was then used to develop the ‘double
Rosalind Franklin’s work on DNA was crucial in discovering the composition of the human body as a whole. Her x-ray photo revealed a double helix structure and she also discovered the A and B form of DNA. She worked through the adversity of being a female in a predominately male dominated realm and made remarkable findings that were eventually stolen. She adapted to a new lab with antiquated technology. Before this discovery, the structure of DNA was thought to be simple. Scientist, Watson and Crick, started with the wrong structure of DNA from a misinterpretation of notes from one of Franklin’s presentations. Unlike Watson and Crick, Rosalind Franklin could explain DNA and how it worked.
The process of DNA replication plays a crucial role in providing genetic continuity from one generation to the next. Knowledge of the structure of DNA began with the discovery of nucleic acids in 1869. In 1952, an accurate model of the DNA molecule was presented, thanks to the work of Rosalind Franklin, James Watson, and Francis Crick. To reproduce, a cell must copy and transmit its genetic information (DNA) to all of its progeny. To do so, DNA replicates following the process of semi-conservative replication. Two strands of DNA are obtained from one, having produced two daughter molecules that are identical to one another and to the parent molecule. This essay reviews the three stages
Due to the DNA’s specificity, samples can be utilised for identification. DNA is a nucleic acid composed of deoxyribose sugar bound to a phosphate group and one of four nitrogenous bases (adenine, guanine, cytosine and thymine). Each section of these three components are referred to as nucleotides, which are joined to the phosphate or sugar of another nucleotide by strong covalent bonds to form a backbone. The nitrogenous bases are joined to complimentary bases of another nucleotide (adenine with thymine, guanine with cytosine) to create a double stranded molecule (Figure 2). To complete the double helical structure, the molecule coils to compact it’s contents. DNA molecules can contain up to two million base pairs, with a human genome containing approximately 3 million base pairs. The random assortment of nitrogenous bases as well as the numerous mutations within certain DNA sequences, results in genetically diverese DNA molecules and genomes between individials.