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Lecture

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


Department
Human Biology
Course Code
HMB265H1
Professor
Stephen Wright

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LECTUREMarch 24, 2011
4 major classes of chromosomal rearrangementsdeletions, duplications, inversions, translocations
Most are caused by double-stranded DNA breakerscausing 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?
oSalivary 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
oTo 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-r ays are major c a use
If pie c e of chromosome is n ot religated in the p o sition, d eletion
Intragenic d eletion o nly on e g ene is affe c ted
Multigenic when man y g enes are d eleted
oPro d u c e more severe p h en o ty p e than intragenic
Df = d eficiency
Usually inviable
Homozyg o tes u sually inviable
Unmasking of re c e s sive
Heterozyg o tes d epen d
Gene inb alanc e
Haploinsufficiency occ urring
Deletion visualiz e d
Deletion loop forming
When p airing d uring meiosis, CDE h as n o p airing p artner, so loop cre a ted
Deletion s are imp ortant
oPhen o men o n of p seu d o d o minanc e allows this
oNormal co n tains rec e s sive all ele of sc a rlet g ene
oDeleted regio n encompas s es sc a rlet g ene
oPhen o ty p e = sc a rlet eyes
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