![]() ![]() They typically occur due to chromosomal abnormalities, such as translocation, duplication, inversion, or deletions of parts of chromosomes or entire chromosomes. In contrast to small-scale changes, large-scale genetic changes are not due to mutations. Įxogenous causes of mutations include ionization radiation, ultraviolet radiation, alkylating agents (mustard gas), polycyclic aromatic hydrocarbons (found in tobacco smoke, charred food, combustion products), crosslinking agents (cyclophosphamide), insertional mutagenesis (integration of viral genome), and other toxins. Small-scale changes are due to mutations, which occur due to several factors, either endogenous or exogenous. Endogenous mechanisms include DNA replication errors (insertion of the incorrect nucleotide), DNA repair errors (failure to remove the incorrect or damaged nucleotide), spontaneous base deamination (loss of the nucleotide’s amine group), base methylation, reactive oxygen species (byproducts of metabolism), and spontaneous hydrolysis of nitrogenous bases. Genomes are unique entities that acquire changes over time and generations due to the cumulative results of both small- and large-scale changes. Mutations can reduce functionality or limit the expression of the gene product, potentially damaging or even killing the cell. Genetic mutations, whether acquired or inherited, form the basis for many disease states, cancer, and aging. However, genetic sequence mutation can occur, which refers to an unintended alteration in a gene’s coding. The cell relies on genes to be accurately and fully copied, transcribed, and translated to create a functioning product, often a specific protein but occasionally RNA as well. Genes, in turn, are a sequence of nucleotides that serve as the basic unit of heredity and code for a specific product, either protein or RNA. One strand goes from 5’ to 3’ and the other from 3’ to 5’, defined by numbering from deoxyribose’s carbon atoms. The two strands are joined together via hydrogen bonds between nucleotides, and they run antiparallel to one another. ![]() This information is derived from the precise order of these base pairs, and as two strands compose every DNA molecule, each strand contains the same coding information. They always pair together with the same partner adenine pairs with thymine (A-T), and cytosine pairs with guanine (C-G). This allows base pairs to be replaced, repaired, or replicated and not ruin DNA’s backbone and subsequent information. These four nucleotides include adenine (A), thymine (T), cytosine (C), and guanine (G). Each nucleotide consists of the sugar deoxyribose, a nitrogenous base, and a phosphate group. Deoxyribonucleic acid (DNA) is a double helix composed of two strands of four types of nucleotides. ![]()
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