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The significance of Discoveries in Genetics and DNA
Our understanding of genetic inheritance and the function of DNA in producing the characteristics of the individual have been developing for more than 150 years. Consider our current state of knowledge. Link genetic characteristics to DNA structure. Explain how DNA through the process of protein synthesis is responsible for the ultimate expression of the characteristics in the organism. Describe how interference in protein synthesis can result in disruption of cellular and bodily processes? How does the significance of one class of proteins, the enzymes, relate to the importance of proper nutrition throughout life?
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Quality of initial posting. 20
Connections and higher order thinking. 10
Reference to supporting readings. 10
Language and Grammar. 10
Total: 50
The significance of Discoveries of Genetics and DNA Sample Answer
The significance of Discoveries of Genetics and DNA
Living things have numerous different expressed traits. However, long before the discovery of the DNA structure by James Watson and Francis Crick in 1953 (Berg, Tymoczko, & Stryer, 2012), the scientific community assumed that the genetics of living things was controlled by proteins, and not by DNA. This essay will discuss the link between genetic traits and DNA. The process of converting a DNA chain into a protein and the result of errors in the fineness of this process will also be described briefly. A special focus will be given to types of proteins called enzymes and their role in nutrition.
DNA as the Hereditary Material
Heredity is the transfer of genetic traits from the parent to the offspring. Genetics is the study of heredity, pioneered in the 1860s by an Austrian monk called Gregor Mendel. He developed the fundamental principles of genetics referred to today as Mendel’s laws of inheritance by cross-breeding garden peas. The Austrian monk deduced that factors that existed in pairs called alleles were accountable for the traits of a living organism. Mendel observed that some traits in the parent plants were expressed in the offspring. He also witnessed that some traits were dominant over others (Mneimneh, 2012; Singh, 2016). Biologist later understood that Mendel’s “factors” were indeed the basic units of DNA called genes that are used as the raw material for synthesizing proteins.
In 1952, a scientist called Chase showed that it was DNA, and not proteins, that controlled the genetic inheritance of individual traits. Chase conducted experiments in which he radiolabelled DNA with phosphorous and proteins with sulfur. A year later, Watson and Crick provided the convincing evidence that DNA, and not proteins, was the genetic material. These two brilliant scientists observed that bacteriophages passed radiolabeled DNA from the parents to the offspring and not radiolabelled proteins (Berg et al., 2012).
The Structure of DNA
DNA (deoxyribonucleic acid) is a linear polymer composed of four different monomers. It has a fixed backbone composed of repeating sugar phosphate units called nucleotides. The sugars are compounds of deoxyribose from which DNA derives its name. Each deoxyribose is joined to one of the four available bases: adenine (A), cytosine (C), thymine (T), and guanine (G). These bases are arranged randomly within a DNA strand.
The structure of DNA proposed by Watson and Crick in the year 1953 supports the role of DNA as the hereditary material. The sequence of bases along a strand of DNA constitutes the genetic information, which is used to make proteins. Watson and Crick deduced that DNA molecules have a three-dimensional structure, which is a double helix made up intertwined strands. The sugar-phosphate backbone lies on the outside of the strands while the bases on the inside allowing the bases to pair to each other using hydrogen bonds. Adenine pairs with thymine (A-T) while guanine pairs with cytosine (G-C). If the double helix is separated into two single strands, then each DNA strand can act as a template for copying its partner by specific base pairing. This is the rationale behind DNA as the hereditary material (Berg et al., 2012).
Gene Expression
As pointed out earlier, a gene is a basic component of DNA that can be converted into a functional unit, either RNA (ribonucleic acid) or a protein. RNA is a nucleic acid that is a bit similar to DNA. It is a linear polymer made up of monomers composed of a sugar, a phosphate, and a nucleic base. However, the sugar in RNA is ribose and not deoxyribose and uracil replaces thymine. In addition, unlike DNA, RNA is a single-stranded molecule. In some viruses, RNA is the hereditary material (Berg et al., 2012).
Gene expression is simply the conversion of DNA into a protein and involves two processes: transcription and translation. Transcription is the conversion of DNA into messenger RNA (mRNA) and is a complex, highly regulated process catalyzed by an enzyme called RNA polymerase. On the other hand, translation is the conversion of mRNA into a functional protein and is affected by the ribosomal machinery. Just like nucleic acids, proteins are also polymers made up of a repertoire of building blocks called amino acids. Protein synthesis is a complex process but the key concept is that a set of three DNA bases encode a single amino acid. A specific correspondence between a set of three bases (referred to as codon) and any one of the twenty amino acids is called genetic code. Several amino acids are joined by peptide bonds to yield a polypeptide or a protein (Berg et al., 2012; Nelson & Cox, 2013).
Proteins are the cellular worker bees, participating in essentially all processes. Some proteins such as keratin and collagen are key structural components, while others called enzymes function as catalysts that accelerate biochemical reactions. Special proteins called receptors bind to ligands such as hormones, neurotransmitters, and drugs to initiate signal cascades that affect other processes within the cell. Even the majority of hormones are proteins. Substrate transporters and ion channels are proteins that facilitate the exchange of molecules between a cell and its environment (Nelson & Cox, 2013).
Genetic Disorders
Occasionally, genetic errors called mutations do occur in the genome and this negatively affects protein synthesis. These gene mutations result in the inability to code the correct order of amino acids to form a protein. Mutations lead to coding of a defective protein that works falsely or the formation of a non-functional one. This interference of protein synthesis disrupts cellular and bodily processes. For instance, the loss of three thymine nucleotides in the gene that encodes for a transport protein called cystic fibrosis transmembrane conductance regulator (CFTR) results in the loss of single amino acid and the subsequent formation of a defective CFTR. This creates a life-threatening condition called cystic fibrosis characterized by a decrease in the secretion of fluids and salts by CFTR. Because of this genetic defect, pancreatic secretion is blocked, and a heavy dehydrated mucus accumulates in the lungs making one susceptible to chronic lung infections (Berg et al., 2012).
Hemoglobin is a protein found in the erythrocytes and plays role in the transport of oxygen in the body. In sickle cell anemia, a single nucleotide mutation results in the synthesis of a defective form of hemoglobin that cannot transport oxygen effectively. Metabolic disorders such as Tay-Sach disease, phenylketonuria, and glucose 6-phosphate dehydrogenase deficiency as well as a good number of autoimmune disorders are all caused by errors in the genetic material that result in the synthesis of non-functional or defective proteins (Berg et al., 2012; Nelson & Cox, 2013).
The Role of Enzymes in Nutrition
Enzymes are proteins that accelerate biological reactions in the body by facilitating the formation of the high-energy transition states. They have pockets called active sites and some are bound to either an organic or an inorganic prosthetic group. Nutrition is the process by which a living organism breaks down food and uses it for growth and development. Nutritionally, enzymes are categorized into two: digestive enzymes and metabolic enzymes (Voet, 2012).
Digestive enzymes are secreted into the gut by body organs such as the salivary glands, the stomach, the pancreas, and the small intestines. Digestive enzymes are secreted when there are substrates (food) in the gut and are thus inducible enzymes. Uncooked food also contains enzymes that help in digestion of food macromolecules. In addition, the gut contains microbial commensals that secrete enzymes that help in digestion. For example, ruminants can digest cellulose, thanks to a microbial cellulose enzyme. Digestive enzymes breakdown proteins, carbohydrates, and lipids into amino acids, monosaccharides, and fatty acids respectively. The building blocks are absorbed through the intestinal wall into the bloodstream (Voet & Voet, 2011).
Metabolic enzymes are present in the cells and are grouped into catabolic and anabolic enzymes. A few are inducible, but a majority are expressed constitutively. Catabolic enzymes further degrade the absorbed building blocks (sugars, amino acids, and fatty acids) to yield energy for use in biosynthetic pathways, muscle contraction, and active transport. Anabolic enzymes catalyse the assembling of the absorbed building blocks to form larger biomolecules such as polysaccharides (glycogen), proteins, lipids (fats and oils), nucleic acids, porphyrins among others (Nelson & Cox, 2013; Voet & Voet, 2011).
Significance of Discoveries of Genetics and DNA Conclusion
DNA is the conventional hereditary material in all cells while RNA is a hereditary material in some viruses. DNA is composed of genes that are transcribed to mRNA, which is then translated to produce a functional protein. These proteins range from transporters, enzymes, receptors, ligands, ion channels, and structural proteins. Errors in the genetic material result in the synthesis of non-functional or defective proteins, which leads to genetic diseases. Enzymes are proteins that play central roles in food nutrition, particularly digestion and metabolism.
Significance of Discoveries of Genetics and DNA References
Berg, J. M., Tymoczko, J. L., & Stryer, L. (2012). Biochemistry (7 ed.): W. H. Freeman and Company.
Mneimneh, S. (2012). Crossing Over…Markov Meets Mendel. Plos Comput Biol, 8(5), e1002462. doi: 10.1371/journal.pcbi.1002462
Nelson, D. L., & Cox, M. M. (2013). Lehninger Principles of Biochemistry (6 ed.): W. H. Freeman and Company.
Singh, R. S. (2016). Science beyond boundary: are premature discoveries things of the past. Genome, 59, 433-437.
Voet, D. (2012). Fundamentals of Biochemistry: Life at the molecular level: Wiley.
Voet, D., & Voet, J. G. (2011). Biochemistry (4th ed.): Wiley.
