Genome size increases as organisms become more complex. Amphibians and plants have genomes which are bigger than those of more recently evolved eucaryotes

Genome size increases as organisms become more complex.

Amphibians and plants have genomes which are bigger than those of more recently evolved eucaryotes.

BSL 2016 - Lecture 1 – Procaryotic and eucaryotic genomes

Chromosome is ONE continuous strand of DNA without ends

Human diploid DNA = 2meters Nucleus is 0.006 mm.

It is efficiently packaged!


DNA packaging is studied by cleaving DNA withnucleases (DNAase1, micrococcocal nuclease)

A ladder of fragments is seen, indicating thatthe DNA is being cut at discrete, regular intervals of about 200bp

Nuclease cuts DNA at unprotected regionsi.e. – those that are “naked” and do not have proteins associated with them


EM of chromatin show the “beadsOn a string structure”

Each bead is a barrel shaped nucleosome made up of 8 histone protein subunits H3,4,2A,2B.

Linker histones may prevent coiledDNA from detaching from thenucleosome.

1st Level of packing


2nd level of packing in which the nucleosomescondense into a helix with 6 nucleosomes perturn – the 30nm solenoid


DNA+Histones=Nucleosome

6 nucleosomes=Solenoid

Chromatin fibre

Chromosomes.


Chromatin structure has to be “opened up” to allowgene transcription, so that controlling proteinsrepressors / activators can bind to the gene promoterand modulate transcription

Gene transcription relies on controlling proteinsrecognising specific sequences on the promotersand binding to them

These controlling proteins cannot bind when DNA is in the chromatin form i.e. already associatedwith proteins which mask binding sites.


Chicken erythroblastsat 14 days synthesiseglobin, cultured MSBcells do not.

Nuclei from both typesOf cell were treatedWith DNase1 and DNA cleaved with BamH1


The Borg link their brains to a collective consciousness via a unique subspace frequency emitted by each drone. This collective consciousness is experienced by the Borg as "thousands“ of voices — they are collectively aware, but not aware of themselves as separate individuals.


Cultured cells are analogous to a borg drone which has been separated from the collective… they lack essential factors…

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Genome size increases as organisms become more complex. Amphibians and plants have genomes which are bigger than those of more recently evolved eucaryotes