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Notes taken during lecture. My laptop battery ran out around ten minutes before lecture ended, so the notes are incomplete. Apologies.

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University of Toronto St. George
Human Biology
Stephen Wright

LECTURE March 24, 2011 4 major classes of chromosomal rearrangements deletions, duplications, inversions, translocations Most are caused by double-stranded DNA breakers causing these chromosomal rearrangements Deletions = specific segment of chromosome is broken in two separate locations, this piece leaves Duplication = segment of DNA duplicated and inserted in another area Inversion = piece of chromosome that is broken, excised, inverted 180 degrees, and reinserted Translocation = piece of chromosome has shifted to another position How can these changes in chromosome structure studied? o Salivary gland chromosomes Very large because they undergo endoreplication Replication of DNA without nuclear division, without cell division Homologous chromosomes stacked on top of each other Many of these chromosomes are actually bound to each other at chromosomal centre Very easily visualized under microscope Charactiersic banding pattern o To show areas of transcipritonal activity and non-activity Stain and look under microscope Locations of bands are same from animal to animal unless there are chromosomal rearrangements Banding patterns have been mapped Deletions X-rays are major cause If piece of chromosome is not religated in the position, deletion Intragenic deletion only one gene is affected Multigenic when many genes are deleted o Produce more severe phenotype than intragenic Df = deficiency Usually inviable Homozygotes usually inviable Unmasking of recessive Heterozygotes depend Gene inbalance Haploinsufficiency occurring Deletion visualized Deletion loop forming When pairing during meiosis, CDE has no pairing partner, so loop created Deletions are important o Phenomenon of pseudodominance allows this o Normal contains recessive allele of scarlet gene o Deleted region encompasses scarlet gene o Phenotype = scarlet eyes
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