John 15:4

©2000 Timothy G. Standish

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


From Sequence to From Sequence to Chromosome:Chromosome:

The Tip of the X Chromosome of The Tip of the X Chromosome of D. MelanogasterD. Melanogaster

Timothy G. Standish, Ph. D.


The Drosophila GenomeThe 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


Telomere

TelomereChromosome MorphologyChromosome Morphology

Arm

Arm Stained polytene chromosomes exhibit distinctive banding patterns

Centromere

Proximal

Distal

Proximal

Distal


Telomere

TelomereChromosome MorphologyChromosome Morphology

Arm

Arm

Centromere

During development chromosome puffs appear which are thought to be correlated with transcriptional activity


Naming Chromosome PartsNaming 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


DrosophilaDrosophila X Chromosome 2b X Chromosome 2b

Figure from http://www.helsinki.fi/~saura/EM/xdiv2.html

In division 2b of the X chromosome, a strange bulge appears in images of polytene chromosomes

Insitu hybridization using cosmid clones mapped to that region show hybridization on the outside of this structure, but not in the middle


CosmidsCosmids A cosmid is a plasmid with the page cos site included

in it The cos site signals for packaging into phage, thus the

plasmid, including a large insert can be packaged into phage particles without having to waste space on genes

A cosmid combined with a cloned insert cannot exceed the 53 kb limit on how much can be packaged into the phage head


An Inverted Repeat May Account An Inverted Repeat May Account For Strange Morphology At X2BFor Strange Morphology At X2B

350 bp

3.5 repeats of satellite like element

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

John 15:4

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