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Mutations https://www.youtube.com/watch? v=HEyCmXL_IM0 Being Brenden Mutations Point mutations single base change base-pair substitution silent mutation no amino acid change redundancy in code missense change amino acid nonsense change to stop codon When do mutations affect the next generation? Point mutation leads to Sickle cell anemia What kind of mutation? Sickle cell anemia Mutations Frameshift shift in the reading frame insertions changes everything “downstream” adding base(s) deletions losing base(s) What’s the value of mutations? Errors of Meiosis Chromosomal Abnormalities AP Biology 2006-2007 Chromosomal abnormalities Incorrect number of chromosomes nondisjunction chromosomes don’t separate properly during meiosis parts of chromosomes are broken off and/or lost during meiosis. or may break and rejoin incorrectly AP Biology Chromosomal abnormalities breakage of chromosomes Deletion: piece of chromosome breaks off and is AP Biology lost. Duplication: chromatid breaks off and attaches to its sister chromatid Chromosomal abnormalities breakage of chromosomes Inversion: chromosome breaks off and is reinserted backwards-or not in the right order Translocation: chromosome breaks off and is added to a nonhomologous chrosomosome AP Biology replication error of Changes in chromosome structure deletion duplication crossing over error of loss of a chromosomal segment repeat a segment inversion reverses a segment translocation AP Biology move segment from one chromosome to another Nondisjunction Baby has wrong chromosome number trisomy cells have 3 copies of a chromosome n+1 AP Biology monosomy cells have only 1 copy of a chromosome n-1 n n trisomy monosomy 2n+1 2n-1 Karyotype A karyotype is a standardized arrangement of all the chromosomes of a cell Homologous chromosomes are paired up, then they are put in order from the LARGEST chromosome pair to the smallest. AP Biology Karyotypes AP Biology Karyotypes AP Biology 2 different sized sex chromosomes = male Down syndrome Trisomy 21 3 copies of chromosome 21 1 in 700 children born in U.S. Chromosome 21 is the smallest human chromosome but still severe effects Frequency of Down syndrome correlates with the age of the mother AP Biology Down’s syndrome •decreased muscle tone at birth •asymmetrical or odd-shaped skull •round head with flat area at the back of the head •slanting eyes •small mouth with protruding tongue •single crease on the palm •slowed growth and development •delayed mental and social skills AP Biology