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Define Mutation
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Mutation occurs when new genes and new alleles originate, which are hanges in the nucleotide sequece of DNA
-occur in somatic cells and are lost when the individual dies |
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Define Point Mutation
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A change as little as one base in a gene can have a significant imapct ona phenotype
ie) sickle-cell disease Harmless because much of the DNA in eukaryote genomes does not code for protein products. And because the genetic code is redundant, point mutations in genes that code for protein may have little effect because they do not alter the proteins amino acid composition ;However some noncoding regions of DNA do regulate the expression of genes. Changes in these regulatory regions of DNA can have profound effects |
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Name one disadvantage and advantage for Mutations that alter gene number or sequence
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-chromosomal mutations that delete, disrupt or rearrange many loci at once are almost certain to be harmful
-however when such mutations leave genes intact, their effects on organisms may be neutral - it may be beneficial ie) trans-location of part of one chromosome to a different chromosome could link genes that together have some heightened positive effect |
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Gene Duplication. Explain.
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Is an important source of variation - harmful
-if such a duplicated segment does not have severe effects, it can persists over generations, providing an expanded genome with new loci that may take on new functions by further mutations and subsequent selection |
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Sexual recombination. Explain
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-sexual reprodution rearragnes alleles into fresh combinations every generation
-sexual recombination is far more important than mutation on a generation to generation to scale in producing the variation that make adaptation possible (phenotypic variation - gene differences resulting from recombination shuffling |
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Of all the mutations that occur, why do only a small fraction become widespread in a gene pool?
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Most mutations occur in somatic cells that do not produce gametes and so are lost when organism dies. Of mutations that do occur in cell lines that produce gametes, many do not have a phenotypic effect on which natural selection can act. Others have a harmful effect and are thus unlikely to spread in a populations from generation to generation becasue they decrease the reproductive success of their bearers
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How does sexual recombination produce variation?
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A population contains a vast number of possible mating combinations and fertilization brings together the gametes of individuals with different genetic backgrounds. Sexual reproduction reshuffles alleles into fresh combinations every generation.
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