essential knowledge 3.b.1:
DESCRIPTION
Essential knowledge 3.B.1:. Gene regulation results in differential gene expression, leading to cell specialization. Both DNA regulatory sequences, regulatory genes, and small regulatory RNAs are involved in gene expression. - PowerPoint PPT PresentationTRANSCRIPT
ESSENTIAL KNOWLEDGE
3.B.1:Gene regulation results in differential gene
expression, leading to cell specialization.
BOTH DNA REGULATORY SEQUENCES, REGULATORY GENES, AND SMALL REGULATORY RNAS ARE INVOLVED IN GENE EXPRESSION.
Regulatory sequences are stretches of DNA that interact with regulatory proteins to control transcription.
• Promoters• Terminators• Enhancers A regulatory gene is a sequence of DNA
encoding a regulatory protein or RNA. Find the regulator gene on the next
slide. What does it do?
Fig. 18-3
Polypeptide subunits that make up
enzymes for tryptophan synthesis
(b) Tryptophan present, repressor active, operon off
Tryptophan(corepressor)
(a) Tryptophan absent, repressor inactive, operon on
No RNA made
Activerepressor
mRNA
Protein
DNA
DNA
mRNA 5
Protein
Inactiverepressor
RNApolymerase
Regulatorygene
Promoter
Promoter
trp operonGenes of operon
Operator Stop
codonStart codonmRN
A
trpA
5
3
trpR trpE trpD
trpC trpB
ABCDE
BOTH POSITIVE AND NEGATIVE CONTROL MECHANISMS REGULATE GENE EXPRESSION IN BACTERIA AND VIRUSES.
The expression of specific genes can be turned on by the presence of an inducer.
The expression of specific genes can be inhibited by the presence of a repressor.
Inducers and repressors are small molecules that interact with regulatory proteins and/or regulatory sequences
Regulatory proteins inhibit gene expression by binding to DNA and blocking transcription (negative control).
Regulatory proteins stimulate gene expression by binding to DNA and stimulating transcription (positive control) or binding to repressors to inactivate repressor function.
Certain genes are continuously expressed; that is, they are always turned “on,” e.g., the ribosomal genes.
Fig. 18-3
Polypeptide subunits that make up
enzymes for tryptophan synthesis
(b) Tryptophan present, repressor active, operon off
Tryptophan(corepressor)
(a) Tryptophan absent, repressor inactive, operon on
No RNA made
Activerepressor
mRNA
Protein
DNA
DNA
mRNA 5
Protein
Inactiverepressor
RNApolymerase
Regulatorygene
Promoter
Promoter
trp operonGenes of operon
Operator Stop
codonStart codonmRN
A
trpA
5
3
trpR trpE trpD
trpC trpB
ABCDE
Is this negative or positive control?
Fig. 18-4a
(a) Lactose absent, repressor active, operon off
DNA
Protein
Activerepressor
RNApolymerase
Regulatorygene
Promoter Operat
or
mRNA 5
3
NoRNAmade
lacI
lacZ
Is this positive or negative control?
NEGATIVE AND POSITIVE CONTROL MECHANISMS http://highered.mcgraw-hill.com/sites/98
34092339/student_view0/chapter16/regulatory_proteins__regulation_by_repression.html
IN EUKARYOTES, GENE EXPRESSION IS COMPLEX AND CONTROL INVOLVES REGULATORY GENES, REGULATORY ELEMENTS AND TRANSCRIPTION FACTORS THAT ACT IN CONCERT.1. Transcription factors bind to specific
DNA sequences and/or other regulatory proteins.
2. Some of these transcription factors are activators (increase expression), while others are repressors (decrease expression).
3. The combination of transcription factors binding to the regulatory regions at any one time determines how much, if any, of the gene product will be produced.
Fig. 18-9-3
Enhancer
TATAbox
PromoterActivator
sDNA
Gene
Distal control
element
Group ofmediator
proteins
DNA-bending
protein
Generaltranscripti
onfactors
RNApolymerase
II
RNApolymerase
II
Transcriptioninitiation
complexRNA
synthesis
ENHANCERS AND REPRESSORS http://highered.mcgraw-hill.com/sites/98
34092339/student_view0/chapter16/transcription_complex_and_enhancers.html
Gene regulation accounts for some of the phenotypic differences between organisms with similar genes.
ESSENTIAL KNOWLEDGE
3.B.2:A variety of intercellular and intracellular signal transmissions mediate
gene expression
SIGNAL TRANSMISSION WITHIN AND BETWEEN CELLS MEDIATES GENE EXPRESSION Cytokines
regulate gene expression to allow for cell replication and division.
SIGNAL TRANSMISSION WITHIN AND BETWEEN CELLS MEDIATES GENE EXPRESSION Mating pheromones in
yeast trigger mating gene expression.
Two haploid yeast of opposite mating types secrete pheromones, grow projections and mate.
SIGNAL TRANSMISSION WITHIN AND BETWEEN CELLS MEDIATES GENE EXPRESSION Ethylene levels cause changes in the
production of different enzymes, allowing fruits to ripen.
SIGNAL TRANSMISSION WITHIN AND BETWEEN CELLS MEDIATES GENE EXPRESSION Seed germination and gibberellin Gibberellins (GAs) are plant hormones
that regulate growth and influence various developmental processes, including stem elongation, and germination
SIGNAL TRANSMISSION WITHIN AND BETWEEN CELLS MEDIATES CELL FUNCTION.Ex 1: HOX genes and their role in
development. Hox genes are a group of related genes
that control the body plan of the embryo along the anterior-posterior (head-tail) axis.
SIGNAL TRANSMISSION WITHIN AND BETWEEN CELLS MEDIATES CELL FUNCTION. Ex 2: P53 is a tumor suppressor
protein p53 is crucial in multicellular
organisms, where it regulates the cell cycle and, thus, functions as a tumor suppressor that is involved in preventing cancer.
As such, p53 has been described as "the guardian of the genome because of its role in conserving stability by preventing genome mutation
SIGNAL TRANSMISSION WITHIN AND BETWEEN CELLS MEDIATES CELL FUNCTION. Morphogenesis “shape” and beginnign--is
the biological process that causes an organism to develop its shape
Example 3: morphogen is a substance governing the pattern of tissue development in the process of morphogenesis, and the positions of the various specialized cell types within a tissue.
More precisely, a morphogen is a signaling molecule that acts directly on cells to produce specific cellular responses depending on its local concentration.
