History of dna
Discovery of DNA
In 1869, proteins were believed to be the hereditary material because there was an abundance of them and they had several different types. Friedrich Miescher investigated the chemical composition of DNA using pus cells. He used pus because he could easily obtain it by collecting used bandages from nearby clinics. Through his experiments, he found and isolated a new molecule. It was found inside the nucleus, so Miescher named it nuclein.
Later in the 1930s, Joachim Hammerling experimented with Acetabularia, a unicellular green alga. This alga is five cms long and has three parts to it, a stalk, cap region and the food which contains the nucleus. In these experiments, Hammerling removed the caps from some and the foot from others. He noticed that the alga without the caps would regrow their caps, but those without feet could not regenerate anything. The theory that Hammerling came up with was that the hereditary information was located in the foot of the alga, possible in the nucleus. He conducted more experiments with different plants and concluded that the hereditary information was in the nucleus.
Then in the 1920s, scientists found that DNA had three main components; a deoxyribose sugar, a phosphate group that is negatively charged and a nitrogenous base. Rosalind Franklin and Maurice Wilkins were each using X-ray diffraction analysis of DNA to determine its structure. James Watson and Francis Crick were also looking for the structure of DNA. Wilkins showed Watson and Crick the data that Franklin had found during her diffraction experiments. Watson and Crick now had the last piece of information they needed and discovered that the structure was a double helix. Then in 1952 it was accepted that DNA is the source of the hereditary information and not protein.
In DNA, there are four nitrogenous bases found in DNA. Adenine and guanine are two double-ringed structures called purines. Thymine and cytosine are single-ringed structures called pyrimidines. These nucleotides are on two anti-parallel strands. Adenine always pairs with thymine and guanine always pairs with cytosine. The sugar and phosphate act as the backbone on the DNA.
In 1869, proteins were believed to be the hereditary material because there was an abundance of them and they had several different types. Friedrich Miescher investigated the chemical composition of DNA using pus cells. He used pus because he could easily obtain it by collecting used bandages from nearby clinics. Through his experiments, he found and isolated a new molecule. It was found inside the nucleus, so Miescher named it nuclein.
Later in the 1930s, Joachim Hammerling experimented with Acetabularia, a unicellular green alga. This alga is five cms long and has three parts to it, a stalk, cap region and the food which contains the nucleus. In these experiments, Hammerling removed the caps from some and the foot from others. He noticed that the alga without the caps would regrow their caps, but those without feet could not regenerate anything. The theory that Hammerling came up with was that the hereditary information was located in the foot of the alga, possible in the nucleus. He conducted more experiments with different plants and concluded that the hereditary information was in the nucleus.
Then in the 1920s, scientists found that DNA had three main components; a deoxyribose sugar, a phosphate group that is negatively charged and a nitrogenous base. Rosalind Franklin and Maurice Wilkins were each using X-ray diffraction analysis of DNA to determine its structure. James Watson and Francis Crick were also looking for the structure of DNA. Wilkins showed Watson and Crick the data that Franklin had found during her diffraction experiments. Watson and Crick now had the last piece of information they needed and discovered that the structure was a double helix. Then in 1952 it was accepted that DNA is the source of the hereditary information and not protein.
In DNA, there are four nitrogenous bases found in DNA. Adenine and guanine are two double-ringed structures called purines. Thymine and cytosine are single-ringed structures called pyrimidines. These nucleotides are on two anti-parallel strands. Adenine always pairs with thymine and guanine always pairs with cytosine. The sugar and phosphate act as the backbone on the DNA.
DNA Replication
DNA is made through a replication process. This replication process is called semi-conservative replication, the DNA splits into two strands, called RNA, and rebuilds the missing half on each strand. These nucleotides are paired in groups of three, and these groups are called codons. When RNA goes through protein synthesis, the codons code for a specific protein to add to a polypeptide chain.
During the replication process, mistakes can happen if the wrong nucleotide is read and coded for, this causes mutations. There are three types of mistakes that can happen, which causes three types of mutations.
Substitution - is when one base in a DNA sequence is replaced by another base.
Deletion - is when a single, pair or group of bases is eliminated from the sequence
Insertion - is when a new nucleotide is added to the sequence
Silent mutations - are when a single nucleotide is changed but the new codon still codes for the same amino acid
Missense mutations - are when one of the nucleotides is changed and the new codon codes for a new amino acid
Nonsense mutations - are when one nucleotide is changed and the new codon is a STOP codon
DNA is made through a replication process. This replication process is called semi-conservative replication, the DNA splits into two strands, called RNA, and rebuilds the missing half on each strand. These nucleotides are paired in groups of three, and these groups are called codons. When RNA goes through protein synthesis, the codons code for a specific protein to add to a polypeptide chain.
During the replication process, mistakes can happen if the wrong nucleotide is read and coded for, this causes mutations. There are three types of mistakes that can happen, which causes three types of mutations.
Substitution - is when one base in a DNA sequence is replaced by another base.
Deletion - is when a single, pair or group of bases is eliminated from the sequence
Insertion - is when a new nucleotide is added to the sequence
Silent mutations - are when a single nucleotide is changed but the new codon still codes for the same amino acid
Missense mutations - are when one of the nucleotides is changed and the new codon codes for a new amino acid
Nonsense mutations - are when one nucleotide is changed and the new codon is a STOP codon