John 15 4 4 Abide in me and

John 15: 4 4 Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me © 2000 Timothy G. Standish

From Sequence to Chromosome: The Tip of the X Chromosome of D. Melanogaster Timothy G. Standish, Ph. D. © 2000 Timothy G. Standish

The Drosophila Genome � 180 million base pairs � 120 Mbp has been sequenced � The sequenced portion is euchromatin thought to be richer in gene sequences than the remaining heterochromatin � Drosophila has a haploid number of 4: 3 autosomes plus 1 sex chromosome � Polytene chromosomes can be easily observed in the salivary glands of larvae © 2000 Timothy G. Standish

Chromosome Morphology Telomere Distal Arm Proximal Centromere Proximal Stained polytene chromosomes exhibit distinctive banding patterns Arm Distal Telomere © 2000 Timothy G. Standish

Chromosome Morphology Telomere Arm Centromere Arm During development chromosome puffs appear which are thought to be correlated with transcriptional activity Telomere © 2000 Timothy G. Standish

Naming Chromosome Parts � Chromosomes are numbered 1 - 3 X and Y � Each chromosome is divided into left (L) and Right (R) arms � Arms are divided into numbered divisions going left to right starting with the X chromosome distal left arm and ending with division 100 on the distal right arm of chromosome 3. � Divisions are divided into lettered subdivisions going left to right © 2000 Timothy G. Standish

Drosophila X Chromosome 2 b In division 2 b of the X chromosome, a strange bulge appears in images of polytene chromosomes � In situ hybridization using cosmid clones mapped to that region show hybridization on the outside of this structure, but not in the middle � Figure from http: //www. helsinki. fi/~saura/EM/xdiv 2. html © 2000 Timothy G. Standish

Cosmids cosmid is a plasmid with the l phage cos site included in it �The cos site signals for packaging into l phage, thus the plasmid, including a large insert can be packaged into phage particles without having to waste space on l genes �A cosmid combined with a cloned insert cannot exceed the 53 kb limit on how much can be packaged into the l phage head �A © 2000 Timothy G. Standish

An Inverted Repeat May Account For Strange Morphology At X 2 B 3. 5 repeats of satellite-like element 350 bp l l These repeated elements resemble the 1. 688 satellite found in units of 1 - 4 on the X chromosome Results indicate that inverted repeats can influence chromosome architecture even when separated by significant distances © 2000 Timothy G. Standish

© 2000 Timothy G. Standish

© 2000 Timothy G. Standish