Mutations
Carcinogens are mutagens in which they induce mutations by modifying DNA or causing chromosomal damage. Genetic mutations have an important role due to genetic changes altering the way that genes control cells function. These genes that are altered typically regulate the way a cell divides and DNA repair mechanisms. Genetic changes that increase cancer risk can be inherited from parents because these changes are present in germ cells, which are reproductive cells in the body. These germline changes are found in every cell of the offspring the parent cells produce. Genetic changes also develop overtime throughout one’s lifetime as a persona ages. The older the cells get, the more prone to mutations they become. Exposures to carcinogens such as exposure to substances like radiation, UV light, or smoke, can damage DNA. Cancer cells have more genetic changes than normal cells. Most mutations that occur within the genome to develop cancer are point mutation.
Types of mutations
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Point mutations- the replacement of a single nucleotide base with another nucleotide.
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Frameshift mutations- addition or deletion of a nucleotide such that the protein sequence from that point onward is altered.
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Chromosomal aberrations- any change in the normal structure or number of chromosomes
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Aneuploidy- chromosome number is not a multiple of the normal haploid (23)
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Polyploidy- more than twice the haploid number of chromosomes
Types of point mutations
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Substitution – occurs when one or more bases in DNA is replaced by the same number of bases
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Missense mutation- occurs when a DNA base pair is substituted from one amino acid for another in the protein made by a gene.
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Nonsense mutation- change in one DNA base pair.
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Frameshift mutation -occurs when the addition or loss of DNA bases changes a gene's reading frame.
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Silent mutation- occurs when the change of a single DNA nucleotide within a protein-coding portion of a one does not affect the sequence of amino acids.
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Insertion- changes the number of DNA bases in a gene by adding piece of DNA.
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Deletion- changed the number of DNA bases by removing a piece of DNA
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Duplication- occurs when a piece of DNA is abnormally copied one or more times.
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Repeat Expansion- is a mutation that increases the number of times that a short DNA sequence is repeated.
The DNA damage caused by mutations is crucial for the development of cancer. Point mutations in the DNA result in the deletion, insertion, or base substitutions the nucleotides. These nucleotides within DNA make up the genetic code which provides specific triplet codes for proteins and enzymes. These enzymes that the DNA codes for control and regulate cell division, proliferation, and DNA repair mechanisms. When these mutations occur within the DNA strand, it can cause a miss read of these codes, ultimately changing their initial function. With the alterations to the functions of these genes, they can no long protect, fix, and regulate the cell cycle. Important genes that are responsible for regulating cell growth, proliferation, and growth factors are oncogenes and tumor suppressor genes
