Eukaryotic Gene control

No OPERONS!!!!

Some Key Points….. Gene control in

eukaryotes is important for development into a multicellular organism

Changing environmental conditions not as important (why?)

Eukaryotes show gene control at all levels, and all seem to be equally important

Eukaryotic Genome Structure

Linear DNA, folded into several chromosomes (approx. 200,000,000 bps) Histone proteins

(tails) 97% of DNA DOES

NOT code for proteins Tandemly repetitive

(satellite) DNA Telomeres &

centromeres

Genome Structure cont…..

Multi gene families Genes that code for

proteins w/ similar functions

May not all be near each other

May be controlled by the same regulatory elements

Gene amplification Multiple copies of a gene Temporary?

Selective gene loss Insect metamorphosis

Gene rearrangements B cell antibodies T cell antigen receptors

Typical Structure of Eukaryotic GenesNO OPERONS!!!

Transcriptional controlChromatin Structure DNA folding/unfolding

Heterochromatin(inactive)

Euchromatin (active)

Transcriptional control

Histone modification Attachment of

acetyl groups (COCH3) to histone tails loosens their hold(active)

Methylation of tails(inactive)

Transcriptional Control cont….

DNA methylation of specific bases(inhibitory) Usually long

term Methylases Demethylases? X-inactivation Development

Patterns passed on to daughter cells

Even more transcriptional control….. enhancers

Sequences of bases

Same sequences used over & over

Distal vs proximal

One enhancer sequence may affect several related genes

Silencer sequences

Cont… Transcription

factors (PROTEINS) Activators vs

repressors Bind to enhancers 100s Gene

Expression/specialization may be due to unique combo of available transcription factors

Post-transcriptional control

mRNA editing Alternative splicing

Transport (or not) to cytoplasm 5’ cap

mRNA degradation-life span of mRNA Poly A tail impt. RNAi ? (Dicer)

DICER

Plus, all the stuff that prokaryotes do!!!

Translational control Initiation complex

Post translational control Protein modification Protein degradation Protein targeting