Title: Regulation of Gene Expression
1Regulation of Gene Expression
2Activity
- Watch video and listen.
- After video, complete worksheet.
3REGULATION
- What is Regulation?
- Every cell in your body has the exact same
genetic code sequence - Each cell will not use all of its genes
- Cells will only turn on the genes that relate to
its function!
4Regulation of Gene Expression by Bacteria
5Bacterial Genomes
- DNA-most is found in the nucleoid region
- Most bacteria have plasmids
- much smaller circles of DNA, each with only a few
genes
6Regulation of metabolic pathways
7(No Transcript)
8Bacterial control of gene expression
- Operon cluster of related genes with on/off
switch - Four Parts
- Promoter where RNA polymerase attaches
- Repressor-blocks polymerase
- Operator on/off, controls access of RNA poly
- Genes code for related enzymes in a pathway
9- Regulatory gene produces repressor protein that
binds to operator to block RNA poly
10Repressible Operon (ON ? OFF)
Inducible Operon (OFF ? ON)
11trp operon
12http//highered.mheducation.com/sites/0072995246/s
tudent_view0/chapter7/the_trp_operon.html
13lac operon
14https//highered.mheducation.com/sites/9834092339/
student_view0/chapter15/the_lac_operon.html
15Answer the following
- What is the difference between inducible and
repressible operons?
16Positive Gene Regulation
- Protein or enzyme can enhance the operon function
- Ex. Occurs in the lac operon
17Fig. 18-5
Promoter
Operator
DNA
lacI
lacZ
RNA polymerase binds and transcribes
CAP-binding site
Active CAP
cAMP
Inactive lac repressor
Inactive CAP
Allolactose
(a) Lactose present, glucose scarce (cAMP level
high) abundant lac mRNA synthesized
Promoter
Operator
DNA
lacI
lacZ
CAP-binding site
RNA polymerase less likely to bind
Inactive CAP
Inactive lac repressor
(b) Lactose present, glucose present (cAMP level
low) little lac mRNA synthesized
18Answer the following
- What is the role of cAMP and CAP? When do we see
these molecules?
19Regulation of Gene Expression in Eukaryotes
20Human Genome
- 3 billion base pairs of DNA
- Only 24,000 genes
- Not all DNA will code for proteins
- Noncoding DNA (Ex. telomeres)
211) Regulation of Chromatin Structure
- chromatin-DNA and proteins
- histones-proteins
- nucleosome-beads that contain DNA and histones
22Regulation of Chromatin Structure
- More transcription acetyl group (-COCH3) is
added to histones and loosens chromatin - Less transcription methyl group (CH3) is added
and chromatin tightly packed
23Genomic Imprinting
- Example of methylation
- involves autosomes
- one allele is silenced
- inherit only one working copy (could come from
mom or dad) - gene is silenced during egg or sperm formation
24Barr Body
- Example of methylation
- One X is turned off in each cell of a female
252) Regulation of Transcription
- Enhancers-increase transcription by binding to
activators - Transcription factors-proteins that help RNA
poly. to bind - Very specific to each cell in the body
26Fig. 18-10
Enhancer
Promoter
Albumin gene
Control elements
Crystallin gene
LENS CELL NUCLEUS
LIVER CELL NUCLEUS
Available activators
Available activators
Albumin gene not expressed
Albumin gene expressed
Crystallin gene not expressed
Crystallin gene expressed
(b) Lens cell
(a) Liver cell
273) Regulation of mRNA
- Alternative RNA splicing-different mRNA can be
made from one gene - Pre-mRNA turns into functional mRNA
- Every mRNA has its own lifespan
- mRNA can translate protein for hours or weeks
284) Regulation of Translation
- microRNAs and small interfering RNAs can either
degrade the mRNA or block the mRNA from being
translated - RNA interference- blocking of gene expression by
noncoding RNAs (miRNA siRNA)
295) Regulation of Proteins
- New protein made must be folded
- Some need to be activated by enzymes
- Proteins may not need to remain in the cells
forever and can be degraded
30(No Transcript)
31Epigenetic Inheritance and the affect of
expression of genes
- changes to the genome that does not directly
involved DNA bases - can be reversed
- environment-stress, diet, nutrition, temperature
can alter expression of genes
32(No Transcript)
33- http//highered.mcgraw-hill.com/olcweb/cgi/pluginp
op.cgi?itswf535535/sites/dl/free/0072437316
/120080/bio31.swfControl20of20Gene20Expressio
n20in20Eukaryotes
34(No Transcript)
35mRNA Alternative Splicing and mRNA processing
- Different mRNA can be produced depending on which
sections are introns or exons - Adding the cap and tail
36mRNA Degradation
- mRNA has a life span
- The mRNA life span is determined by sequences in
the leader and trailer regions (UTR sections)
37Regulation of Translation
- The initiation of translation can be blocked by
regulatory proteins that bind to sequences or
structures of the mRNA
- Proteasomes-giant protein complexes that bind
protein molecules and degrade them
Proteasome and ubiquitin to be recycled
Ubiquitin
Proteasome
Ubiquitinated protein
Protein to be degraded
Protein fragments (peptides)
Protein entering a proteasome
38- Regulation of mRNA
- micro RNAs (miRNAs) and small interfering RNAs
(siRNAs) can bind to mRNA and degrade it or block
translation
39(No Transcript)
40Summary of Eukaryotic Gene Expression
41Embryonic Development of Multicellular Organisms
42Embryonic DevelopmentZygote ? Organism
- Cell Division large identical cells through
mitosis - Cell Differentiation cells become specialized in
structure function - Morphogenesis creation of form organisms
shape
43Determination irreversible series of events that
lead to cell differentiation
44- Cytoplasmic determinants maternal substances in
egg distributed unevenly in early cells of embryo
45- Induction cells triggered to differentiate from
neighboring cells - Cell-Cell Signals molecules produced by one cell
influences neighboring cells - Ex. Growth factors
46(No Transcript)
47Pattern formation setting up the body plan
(head, tail, L/R, back, front)
48Morphogens substances that establish an embryos
axes
49Homeotic genes master control genes that control
pattern formation (ex. Hox genes)
50Cancer results from genetic changes that affect
cell cycle control
51Control of Cell Cycle
- Proto-oncogene stimulates cell division
- Tumor-suppressor gene inhibits cell division
- Mutations in these genes can lead to cancer
52- Gene that stimulates normal cell growth division
- Mutation in proto-oncogene
- Cancer-causing gene
- Effects
- Increase product of proto-oncogene
- Increase activity of each protein molecule
produced by gene
53Proto-oncogene ? Oncogene
54Genes involved in cancer
- Ras gene stimulates cell cycle (proto-oncogene)
- Mutations of ras occurs in 30 of cancers
- p53 gene tumor-suppresor gene
- Functions halt cell cycle for DNA repair, turn
on DNA repair, activate apoptosis (cell death) - Mutations of p53 in 50 of cancers
55- Cancer results when mutations accumulate (5-7
changes in DNA) - Active oncogenes loss of tumor-suppressor genes
- The longer we live, the more likely that cancer
might develop
56Fig. 19.12
Growth factor
MUTATION
1
Hyperactive Ras protein (product
of oncogene) issues signals on its own
Ras
G protein
GTP
3
Ras
GTP
Receptor
Protein kinases (phosphorylation cascade)
2
4
NUCLEUS
Transcription factor (activator)
5
DNA
Gene expression
Protein that stimulates the cell cycle
(a) Cell cyclestimulating pathway
Protein kinases
2
MUTATION
Defective or missing transcription factor,
such as p53, cannot activate transcription
Active form of p53
3
UV light
DNA damage in genome
1
DNA
Protein that inhibits the cell cycle
(b) Cell cycleinhibiting pathway
EFFECTS OF MUTATIONS
Protein overexpressed
Protein absent
Cell cycle not inhibited
Cell cycle overstimulated
Increased cell division
(c) Effects of mutations
57Summary
- Embryonic development occurs when gene regulation
proceeds correctly - Cancer occurs when gene regulation goes awry