Biological Anthropology Study Set 1
Quiz 3 :
Introduction to Genetics and Genomics
All animals are made up of cells, with each cell containing various components that attribute to cellular functions. For example, the mitochondria are one of many organelles located within the cell's structure and functions as the cell's powerhouse, generating fuel for cellular activities. The most important organelle is the cell's nucleus, which contains deoxyribonucleic acid (DNA). DNA is the core part of the biology of the cell and is the main component in heredity as it functions to replicate, synthesize protein and regulate itself during the process of replication. The fact that most living forms use DNA and the same code to form the basis of their structures implicates that: • Most life forms on earth may have originated from a common cell. • Throughout the history of earth, through its environmental changes and stresses, cellular DNA is the most successful molecular structure to survive and adapt. From an evolutionary perspective, consider that through time and environmental stresses, the cell was able to survive and adapt to various environmental stresses and subsequently, evolve. Cells that were not able to adapt and survive environmental stresses were not able to pass on its genetic material, while cells with the traits or organelles that allowed it to survive and flourish in changing environmental conditions were able to pass on its genetic material. Time and environment were able to shape the cell into what it is today, containing the necessary organelles that it possesses and ensuring that DNA, with its double-helix structure, 4-nucleotide bases, super-coiled into chromosomes was the best arrangement and structure in ensuring that genetic materials are successfully passed from generation to generation.
DNA, or deoxyribonucleic acid, has three main functions including: • Replication (making copies of itself) • Protein synthesis (creating molecules that make-up the organism) • Regulation (regulating the processes of replication and protein synthesis) Protein synthesis is the process by which DNA sequences are coded to produce proteins. Proteins are the basic building blocks for the organic structures that make up the organism and are composed of folded strings of compounds called amino acids. A string of amino acids are called polypeptides. In a DNA strand, there are nucleotide base sequences that are to be coded and read by machinery in the cytoplasm in three nucleotide base sequences, called triplets. These three nucleotide base sequences translate to mean a specific amino acid, which is subsequently translated into a string of amino acids that unfolds and becomes a protein. It is the proteins that form alleles, a specified unit of heredity that causes a specified observable trait. However, of all the triplets and sequences of nucleotide bases that correlate to form specific amino acids, to proteins to alleles, there are only 20 amino acids in the human body. Therefore, approximately 2% of DNA codes for proteins, while a vast 98% of DNA are inactive. The inactivity of 98% of DNA means that not only does DNA not have any active genes, much of the genetic material in the gene may not code for anything at all. It is inferred that the inactive DNA is essential as a reservoir of variation and is tied with the idea of evolvability. Evolvability is theorized by biologists that the human genome be vast enough for genetic variations to occur as a response to natural selection. In other words, it may not be unreasonable to speculate that noncoding, inactive DNA serves as a hedge, or protection, against future selection. The human genome is similar to the chimpanzee genome in that approximately 2% of DNA codes for protein, while approximately 98% of DNA is non-protein coding DNA. However, keeping in mind that for both humans and chimpanzees, 98% of DNA is considered inactive, when it is said that human and chimpanzees share 98% of their DNA, that 98% refers only to the 2% DNA that codes for proteins. The statement that humans and chimpanzees are 98% identical is true, because chimpanzees share 98% (a vast majority) of the 2% of human DNA that codes for proteins. Thus, a majority of our body parts from organs and tissues, to hair and eyes are similar. Conversely, it can be inferred that humans differ from chimpanzees by roughly 2% because of variations in human beings from skin color, eyes, nose variations to hair color and height.
DNA, or deoxyribonucleic acid, has three main functions including: • Replication (making copies of itself) • Protein synthesis (creating molecules that make-up the organism) • Regulation (regulating the processes of replication and protein synthesis) As DNA regulates the replication and protein synthesis processes, it has several repair mechanisms that ensure accurate DNA replication: • The first repair mechanism is a monitoring system that examines the appropriate enzymes and nucleotide bases. • The second repair mechanism is a proofreading system that ensures that the correct nucleotide bases are paired (adenine to thymine, cytosine to guanine). • If there are errors detected in the replicated DNA segment, the third repair mechanism will make the necessary corrections or completely void the DNA segment altogether. • The fourth repair mechanism removes damaged DNA segments and creates replacement DNA segments as a result of external causes, such as radiation. When DNA regulation and self-correction breaks down and is no longer effective, genetic mutations occur. A genetic mutation means that there is a change in the nucleotides of the DNA. When DNA self-correction is no longer effective, the nucleotides may be switched (adenine for a cytosine, for example). The results can be a triplet coding combination that either reads for the same amino acid (and subsequent protein), or render the protein non-functional. However, the triplet coding due to switched nucleotides can translate into a whole new protein that is expressed as a physical trait that benefits the organism in an environment. The physical trait may aid the organism in surviving a harsh environmental stress. In such cases, the breakdown of DNA self-correction is beneficial.