Mutations

Mutations - Mutations Importance of Mutation mutations are...

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Mutations Importance of Mutation mutations are the source of all genetic variation without variation by mutation organisms could not adapt to changing environments many mutations have detrimental effects mutations are the source of many human diseases and disorders mutations are heritable changes in the DNA Categories of Mutations Somatic Mutations: arise in the somatic tissues that do not produce gametes o through mitosis the mutation in somatic cells is passed on to the daughter cells Germ-line Mutations: arise in cells that ultimately produce gametes o can be passed to future generations Types of Gene Mutations Base Substitutions: the simplest type of gene mutation. Alters a single nucleotide in the DNA and can lead to a base-pair substitution o Transition: a purine is replaced by a different purine or a pyrimidine is replaced by a different pyrimidine o Transversion: a purine is replaced by a pyrimidine or a pyrimidine is replaced by a purine Insertions and Deletions: involves the addition of the removal of one or more nucleotide pairs and is the most commonly occurring mutation o Frameshift mutations: changing in the reading frame of the gene can be caused by insertions and deletions within sequences that encode proteins Expanding Trinucleotide Repeats: are mutations in which copies of a trinucleotide may increase greatly in number; regions of DNA that consist of repeated copies of three nucleotides such as the fragile-X chromosome Phenotypic effects of mutations: realized when the mutant is compared with the most common phenotype in natural populations of the organism (the wild-type phenotype) o Forward Mutations: a mutation that alters the wild-type phenotype o Reverse Mutation: changes a mutant back into the wild-type o Missense Mutation:alters a sense codon in mRNA resulting in a different amino acid in the protein o Nonsense Mutation: changes a sense codon (one that specifies an amino acid) into a nonsense codon (one that terminates translation) causing premature termination of translation o
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Mutations - Mutations Importance of Mutation mutations are...

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