1. Thursday, March 2, 2017 GOALS: Finish Ghost in your Genes
Explain regulation of transcription and translation for eukaryotes
RNAi
HOMEWORK:
Watch the RNAi video and answer the questions. You must have this done on Monday for discussion.
Get ready for the Tuesday/Wednesday Exam

2. Chapter 18: DNA Packaging and Eukaryotic Gene Regulation
Eukaryotic DNA is linear
Chromosomes of DNA packaged during interphase as chromatin
Chromatin condenses (further coils and folds) into chromosomes before mitosis
On average, chromosomes contain 2 x 108 nucleotide pairs
An ‘unpackaged’ chromosome of this size would be 6cm long!
Detailed packaging info: see figure 19.1
Compare/contrast DNA packaging for eukaryotes vs. prokaryotes!

3. Histone proteins contain large amounts of positively- charged amino acids. Why?
+ DNA called a
nucleosome!
Distinguish between heterochromatin & euchromatin

4. DNA: Make a protein or not!
97% of DNA in humans does NOT code for proteins
What does non-protein coding DNA do?
Introns
Tandem Repeats: may cause disorders such as Fragile X Syndrome and Huntington’s Chorea
Regulatory: enhance or prevent transcription
Make rRNA or tRNA or microRNA for RNAi!!!
Interspersed, Repetitive DNA: Alu elements
Interspersed, Repetitive DNA segments occur throughout the genome. Caused by transposons - moveable genetic elements. Each repeat is 100’s to 1,000’s of base pairs long. Copies are not completely identical to each other. In humans, 5% of DNA composed of repeats called Alu elements (300 bp long). Alu elements ARE transcribed, but function of RNA is unknown.

5. Regulation of Eukaryotic Gene Expression
Not all genes are transcribed & translated in every cell
The genes that are active at one time in the life of a cell will NOT be active during a different developmental time!

6. There are several places where regulation occurs in the process of gene expression: (figure 19.7)
DNA packaging: methylation and acetylation
Transcription: transcription factors, lipid hormones,
RNA editing: alternative splicing
Translation: RNAi (post-transcriptional silencing)
Post-Translational Modification of Protein: protein cleavage, protein modification in ER or golgi apparatus (add lipids or oligosaccharides)

7. Opportunities for control of gene expression in eukaryotic cells
Figure 18.6:
Opportunities for control
of gene expression in
eukaryotic cells
KNOW THIS

8. DNA Packaging Affects Expression
Heterochromatin (highly condensed) DNA is usually NOT expressed because transcription proteins cannot access DNA.
Genes around histones or attached to internal nuclear scaffolds are also NOT expressed
Some nucleotides, specifically cytosine, are methylated (add -CH3 group). If DNA is methylated, it is usually NOT expressed.

9. Histone acetylation: add -COCH3 group to amino acids of histone proteins. Addition of group changes shape of histone, so they grip DNA less tightly, therefore DNA is expressed

10. Epigenetics What kind of rat mother are you?
Go back to the Ghost in Your Genes Worksheet or the Lick your Rat website

11. Structure of a Eukaryotic Gene
Control Elements: Upstream of gene (on DNA) that bind to transcription factors and therefore facilitate transcription
Transcription factors are ESSENTIAL for RNA polymerase to bind DNA and begin transcription of gene sequence
Proximal Control Elements: Near gene/promoter
Distal Control Elements: far from promoter, upstream OR downstream

12. Promoter: Sequence of DNA where transcription begins; TATA box sequence
Exon: sequence of nucleotides used to make a protein
Intron: sequence of nucleotides not used to make protein; excised by spliceosomes
Terminator: sequence of nucleotides downstream from last exon (signals RNA polymerase to cease transcription)

13. Eukaryotic Gene Structure and Primary Transcript

14. 1. Activators bind to enhancers on DNA
Model for enhancer action
1. Activators bind to enhancers on DNA
2. DNA bends
3. Other transcription factors bind to both activator & promoter for complete transcription initiation complex