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BIOL 2P02 (103)

November 27.docx

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Adonis Skandalis

November 27  How different genetically are humans from each other? What is the source of variability  Genetic variations underlie phenotypic differences  What we are is described as genes  Genetic variations cause inherited disease o Genetic diseases, complex diseases, environmental diseases  In genetic diseases and complex diseases mostly genes but for environmental it is mostly environmental  Variable allows people to associate genetic variations with different diseases  Locus – abstract reference to a gene/maker location on the chromosome  Allele – a specific variant from of a gene/marker at a particular locus  We are different because we carry different alleles  The reason why females are susceptible for breast cancer is because they have a specific allele that exposes them to breast caner  Single nucleotide differences is what makes us different from each other Forms of genetic variations  Single nucleotide substitution: replacement of one nucleotide with another  Microsatellites or minisatellites: these tandem repeats often present high levels of inter- and intra-specifif polymorphism  Iif repeats are in the gene, too many repeats. Once you get above a certain amount of repeats, you develop a disease. Very important  Deletions or insertions: loss or addition of one or more nucleotides  Changes in chromosome number, segmental rearrangements and deletions  Most abundant change is single nucleotide polymorphisms (SNP)…. Called a variant o Can be a polymorphisms under certain conditions  We assume that person has the change throughout their body  If person carries change, have to compare to the population  If the change that one has is very rare, is a recent mutation.  About 90% of all human genetic variations are SNP  Can casue an entire amino acid change is they are coding, they do not have to express genes, don’t have to have a phenotype  Mostly found in single nucleotide changes  Single base changes o Transitions: purine to purine or pyrimidine to pyrimidine  A to g or vice versa and T to C and C to T o Transversions: purine  What is the difference between SNP and mutation?  Sickle cell anemia is SNP  For a variation to be considered a SNP. It must occur in at least 1% of the population  Polymorphism: variations in DNA sequence (substitutions, deletions, insertion) that are present at a frequency greater than 1% population  Mutation
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