The evolutionary relationship between organisms has been measured and monitored using DNA and proteins from these organisms. This is because, members of the same species have the larger fraction of their genes (DNA) and proteins being common. Genes and products of genes (proteins) can be considered as historical documents passed from parents to offspring and similarity between genes and proteins of members of different species therefore acts as prove of evolution. However, the validity of using DNA and proteins as evolutionary tape measures depend on the accessibility of this evolutionary information. How can biologists therefore access hereditary information of organisms? It is through application of the concepts of linear sequence of nucleotides and testable hypotheses. Without these concepts, it would be difficult and inefficient to compare the evolutionary information of various organisms.
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This concept of linear sequence of nucleotides provides a deeper understanding of inheritance and therefore makes it possible to use DNA and protein as evolutionary tape measures. It is based on several facts. The synthesis of each protein in an organism depends on the sequence of amino acids in the polypeptides making up the protein. A unit of inheritance known as the gene determines this sequence of amino acids. Each gene is a sequence of nucleotides along a DNA strand. It is made up of four components: a pentose sugar, a nitrogenous base and a phosphate group. “The nitrogenous bases are (Thymine (T), Adenine (A), Guanine (G), and Cytosine (C),” (“How genes work,” 2006, para.2). All genetic information is written using the four-letter alphabet representing the nucleotides since each nucleotide has only one base. The linear sequence of three nucleotides forms a three-letter codon, for example AAA or CAG that will determine the protein to be formed. The code is universal; this means that except for a few minor exceptions, all animals on Earth use the same code (Sengbusch, 2003). The code is also degenerate meaning that an amino acid can also be coded by several codes (“DNA,” 2009, para.6). What this implies is that, by determining the nucleotide sequence in DNA and proteins of members of a species, hereditary relationship between these species can be measured. Through this concept, genetic information through out a generation is measured and thereby, the evolution.
In scientific work like monitoring evolution, testable hypotheses are of great importance. A testable hypothesis means that the hypothesis must be scientifically testable, repeatable and must provide clear results that can be used to disapprove or approve the hypothesis. This concept of testable hypothesis is important in monitoring evolution since the hypotheses put forward by the biologists can be tested and proved or disapproved depending on the results. For example, biologists can hypothesis that if two species are closely related, they share a common nucleotide sequence in their DNA. However, this hypothesis does not provide useful information until the DNA and protein sequences from the species are analyzed.
In conclusion, DNA and proteins can be used to as tape measures of evolution but their usage depends on the concept of linear sequence of nucleotides. The concept allows for a molecular analysis of the DNA and protein molecules thereby simplifying the process of comparison. Testable hypotheses play an important role in this analysis in that the hypotheses put forward by the biologists can be proved or disapproved using actual results obtained.
Sengbusch, P. V. (2003). The genetic code. University of Hamburg. Web.
“How genes work,” (2006). The new genetics. National Institute of General Medical Sciences. Web.
“DNA”. DNA, genes and chromosomes. University of Leicester. 2010, Web.
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