Chapter 19:Chapter 19:
EukaryoticEukaryotic Genomes-Genomes-
Organization,Organization,
Regulation, & EvolutionRegulation,...
Objectives for this lecture
1. Understand how DNA is organized, and how that
organization helps us control gene expression...
Terms definitions
1. Gene expression
2. Regulation
3. Transcription
4. Translation
5. mRNA
6. Protein
A. Controls, rules
B...
for your notes…
Underlined and
colored text most
critical
HOW DNA IS
ORGANIZED
Section 1
•Eukaryotic genomes have much more DNA
than prokaryotes do
•Eukaryotic DNA must be specially organized to
maintain efficie...
Chromatin Structure is Based on
Successive Levels of DNA Packing
DNA in a eukaryotic chromosome
White center =
main axis o...
•A special problem: All prokaryotic & eukaryotic
cells must be able to express certain genes as needed
•All cells contain ...
DNA organization changes throughout the cell cycle:
•Histones are proteins that are like spools that DNA
wraps around
•A
nucleosome
is a section
of DNA
wrapped
around 2
histo...
Higher Levels of DNA Packing
•The 10nm fiber continues to coil to 30nm as linker
DNA attracts to histone tails and the H1 ...
Higher Levels of DNA Packing
•The 30nm fiber then
forms looped domains
•Protein scaffolds are
made of non-histone
proteins...
Regulation of Chromatin StructureRegulation of Chromatin Structure
•Genes in highly condensed heterochromatin are
usually ...
DNA MethylationDNA Methylation
•Genes that are not expressed are usually heavily
methylated
Acetyl groups bind to
histone tails, keep the
DNA loose so
transcription can
happen
Histone AcetylationHistone Acetylation
QUICK THINKQUICK THINK
Draw the levels
of organization
of DNA,
putting methyl
and acetyl
groups
REGULATION OF GENE EXPRESSION BY CONTROL OF
TRANSCRIPTION
Section 2
First, a review of genes & their transcripts:
promoter
1. Transcription begins when a cluster of proteins called
a transcr...
Control elements : sequences of non-coding DNA that
regulate transcription by binding to certain proteins.
*They are often...
Proximal control elements• _________________________ are close to the promoter
•__________________________ , AKA enhancers...
LE 19-6
Distal control
element Activators
Enhancer
DNA
DNA-bending
protein
TATA
box
Promoter
Gene
General
transcription
fa...
RNA Processing
The original RNA transcript can
produce various mRNAs depending
on which part of the pre-mRNA is
treated as...
mRNA DegradationmRNA Degradation
Enzymes may
remove the 5’ cap
& the poly-A tail.
This exposes the
mRNA to
nucleases that
...
microRNAs (miRNAs)
miRNAs are single-stranded RNA molecules that bind to mRNA
to either degrade the mRNA or block translat...
REGULATION AFTER TRANSCRIPTION HAS OCCURRED
Section 3
Post-Transcriptional RegulationPost-Transcriptional Regulation
Protein production
can be controlled
at other points
before...
Regulation of Translation
Regulatory proteins may bind to the 5’ end of mRNA,
which makes the ribosome unable to attach
Protein Processing & Degradation
•Proteins that are to be degraded are tagged with a ubiquitin
marker protein
•Giant prote...
LE 19-3
Signal
NUCLEUS
DNA
RNA
Chromatin
Gene available
for transcription
Gene
Exon
Intro
Transcription
Primary transcript...
QUICK THINK
Once mRNA is in the cytoplasm, describe some ways that
regulate the amount of active protein in the cell
AP Bio Ch 19.1 & 19.2
AP Bio Ch 19.1 & 19.2
AP Bio Ch 19.1 & 19.2
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AP Bio Ch 19.1 & 19.2

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AP Bio Ch 19.1 & 19.2

  1. 1. Chapter 19:Chapter 19: EukaryoticEukaryotic Genomes-Genomes- Organization,Organization, Regulation, & EvolutionRegulation, & Evolution
  2. 2. Objectives for this lecture 1. Understand how DNA is organized, and how that organization helps us control gene expression 2. Understand how regulation of transcription helps us control gene expression 3. Understand how regulation of translation helps us control gene expression
  3. 3. Terms definitions 1. Gene expression 2. Regulation 3. Transcription 4. Translation 5. mRNA 6. Protein A. Controls, rules B. Produced during transcription C. DNA  RNA  protein  cell product D. The product of translation E. DNA  mRNA F. mRNA  protein Warm up, matching
  4. 4. for your notes… Underlined and colored text most critical
  5. 5. HOW DNA IS ORGANIZED Section 1
  6. 6. •Eukaryotic genomes have much more DNA than prokaryotes do •Eukaryotic DNA must be specially organized to maintain efficiency Chromatin: DNA wrapped around protein
  7. 7. Chromatin Structure is Based on Successive Levels of DNA Packing DNA in a eukaryotic chromosome White center = main axis of the chromosome Red loops = DNA that is being actively transcribed
  8. 8. •A special problem: All prokaryotic & eukaryotic cells must be able to express certain genes as needed •All cells contain the same, complete set of DNA •Cells are different because they express different genes
  9. 9. DNA organization changes throughout the cell cycle:
  10. 10. •Histones are proteins that are like spools that DNA wraps around •A nucleosome is a section of DNA wrapped around 2 histones.
  11. 11. Higher Levels of DNA Packing •The 10nm fiber continues to coil to 30nm as linker DNA attracts to histone tails and the H1 histone
  12. 12. Higher Levels of DNA Packing •The 30nm fiber then forms looped domains •Protein scaffolds are made of non-histone proteins •Looped domains compact further to form the characteristic metaphase chromosome
  13. 13. Regulation of Chromatin StructureRegulation of Chromatin Structure •Genes in highly condensed heterochromatin are usually not expressed •Genes in the looser packing of euchromatin usually are expressed
  14. 14. DNA MethylationDNA Methylation •Genes that are not expressed are usually heavily methylated
  15. 15. Acetyl groups bind to histone tails, keep the DNA loose so transcription can happen Histone AcetylationHistone Acetylation
  16. 16. QUICK THINKQUICK THINK Draw the levels of organization of DNA, putting methyl and acetyl groups
  17. 17. REGULATION OF GENE EXPRESSION BY CONTROL OF TRANSCRIPTION Section 2
  18. 18. First, a review of genes & their transcripts: promoter 1. Transcription begins when a cluster of proteins called a transcription initiation complex binds to the of the gene RNA pol II2. The enzyme transcribes the gene into a molecule of pre-mRNA a 5’ cap & poly-A tail3. RNA processing includes the addition of as well as cutting out the introns
  19. 19. Control elements : sequences of non-coding DNA that regulate transcription by binding to certain proteins. *They are often found upstream of eukaryotic genes
  20. 20. Proximal control elements• _________________________ are close to the promoter •__________________________ , AKA enhancers, are farther away and can even be within introns Distal control elements
  21. 21. LE 19-6 Distal control element Activators Enhancer DNA DNA-bending protein TATA box Promoter Gene General transcription factors Group of mediator proteins RNA polymerase II RNA polymerase II RNA synthesis Transcription Initiation complex
  22. 22. RNA Processing The original RNA transcript can produce various mRNAs depending on which part of the pre-mRNA is treated as introns & which are treated as exons
  23. 23. mRNA DegradationmRNA Degradation Enzymes may remove the 5’ cap & the poly-A tail. This exposes the mRNA to nucleases that break it down.
  24. 24. microRNAs (miRNAs) miRNAs are single-stranded RNA molecules that bind to mRNA to either degrade the mRNA or block translation miRNA starts off as a segment of RNA that is H-bonded to itself, then it gets chopped into smaller pieces by an enzyme called dicer
  25. 25. REGULATION AFTER TRANSCRIPTION HAS OCCURRED Section 3
  26. 26. Post-Transcriptional RegulationPost-Transcriptional Regulation Protein production can be controlled at other points before the protein becomes fully functional
  27. 27. Regulation of Translation Regulatory proteins may bind to the 5’ end of mRNA, which makes the ribosome unable to attach
  28. 28. Protein Processing & Degradation •Proteins that are to be degraded are tagged with a ubiquitin marker protein •Giant protein complexes called proteasomes recognize and break down the tagged proteins
  29. 29. LE 19-3 Signal NUCLEUS DNA RNA Chromatin Gene available for transcription Gene Exon Intro Transcription Primary transcript RNA processing Cap Tail mRNA in nucleus Transport to cytoplasm CYTOPLASM mRNA in cytoplasm Translation Degradation of mRNA Polypeptide Cleavage Chemical modification Transport to cellular destination Degradation of protein Active protein Degraded protein Eukaryotic gene expression can be controlled at multiple steps 1. 2. 3. 4. 5. 6.
  30. 30. QUICK THINK Once mRNA is in the cytoplasm, describe some ways that regulate the amount of active protein in the cell

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