KEY CONCEPTS
18.1 Bacteria often respond to environmental change by
regulating transcription
18.2 Eukaryotic gene expression is regulated at many stages
18.3 Noncoding RNAs play multiple roles in controlling gene
expression
18.4 A program of differential gene expression leads to the different cell types in a multicellular organism
18.5 Cancer results from genetic changes that affect cell cycle control
KEY CONCEPTS
48.1 Neuron structure and organization reflect function in information transfer
48.2 Ion pumps and ion channels establish the resting potential of a neuron
48.3 Action potentials are the signals conducted by axons
48.4 Neurons communicate with other cells at synapses
Chapter 50: Sensory and Motor MechansimsAngel Vega
KEY CONCEPTS
50.1 Sensory receptors transduce stimulus energy and transmit signals to the central nervous system
50.2 The mechanoreceptors responsible for hearing and
equilibrium detect moving fluid or settling particles
50.3 The diverse visual receptors of animals depend on light-
absorbing pigments
50.4 The senses of taste and smell rely on similar sets of sensory receptors
50.5 The physical interaction of protein filaments is required for muscle function
50.6 Skeletal systems transform muscle contraction into
locomotion
KEY CONCEPTS
12.1 Most cell division results in genetically identical daughter cells
12.2 The mitotic phase alternates with interphase in the cell cycle
12.3 The eukaryotic cell cycle is regulated by a molecular
control system
KEY CONCEPTS
48.1 Neuron structure and organization reflect function in information transfer
48.2 Ion pumps and ion channels establish the resting potential of a neuron
48.3 Action potentials are the signals conducted by axons
48.4 Neurons communicate with other cells at synapses
Chapter 50: Sensory and Motor MechansimsAngel Vega
KEY CONCEPTS
50.1 Sensory receptors transduce stimulus energy and transmit signals to the central nervous system
50.2 The mechanoreceptors responsible for hearing and
equilibrium detect moving fluid or settling particles
50.3 The diverse visual receptors of animals depend on light-
absorbing pigments
50.4 The senses of taste and smell rely on similar sets of sensory receptors
50.5 The physical interaction of protein filaments is required for muscle function
50.6 Skeletal systems transform muscle contraction into
locomotion
KEY CONCEPTS
12.1 Most cell division results in genetically identical daughter cells
12.2 The mitotic phase alternates with interphase in the cell cycle
12.3 The eukaryotic cell cycle is regulated by a molecular
control system
KEY CONCEPTS
10.1 Photosynthesis converts light energy to the chemical energy of food
10.2 The light reactions convert solar energy to the chemical energy of ATP and NADPH
10.3 The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar
10.4 Alternative mechanisms of carbon fixation have evolved in hot, arid climates
Chapter 16: Molecular Basis of InheritanceAngel Vega
KEY CONCEPTS
16.1 DNA is the genetic material
16.2 Many proteins work together in
DNA replication and repair
16.3 A chromosome consists of a DNA molecule packed together with proteins
KEY CONCEPTS
45.1 Hormones and other signaling molecules bind to target
receptors, triggering specific response pathways
45.2 Feedback regulation and coordination with the nervous system are common in endocrine signaling
45.3 Endocrine glands respond to diverse stimuli in regulating homeostasis, development,
and behavior
Bio chapter 2: A Chemical Connection to BiologyAngel Vega
KEY CONCEPTS
2.1 Matter consists of chemical elements in pure form and
in combinations called compounds
2.2 An element’s properties depend on the structure of its atoms
2.3 The formation and function of molecules depend on chemical bonding between atoms
2.4 Chemical reactions make and break chemical bonds
KEY CONCEPTS
13.1 Offspring acquire genes from parents by inheriting
chromosomes
13.2 Fertilization and meiosis alternate in sexual life cycles
13.3 Meiosis reduces the number of chromosome sets from diploid to haploid
13.4 Genetic variation produced in sexual life cycles contributes to evolution
KEY CONCEPTS
43.1 In innate immunity, recognition and response rely on traits
common to groups of pathogens
43.2 In adaptive immunity, receptors provide pathogen-specific
recognition
43.3 Adaptive immunity defends against infection of body fluids and body cells
43.4 Disruptions in immune system function can elicit or exacerbate disease
KEY CONCEPTS
11.1 External signals are converted to responses within the cell
11.2 Reception: A signaling molecule binds to a receptor protein, causing it to change shape
11.3 Transduction: Cascades of molecular interactions relay
signals from receptors to target molecules in the cell
11.4 Response: Cell signaling leads to regulation of transcription or cytoplasmic activities
11.5 Apoptosis integrates multiple cell-signaling pathways
KEY CONCEPTS
4.1 Organic chemistry is the study of carbon compounds
4.2 Carbon atoms can form diverse molecules by bonding to four other atoms
4.3 A few chemical groups are key to molecular function
KEY CONCEPTS
9.1 Catabolic pathways yield energy by oxidizing organic
fuels
9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
9.3 After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules
9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis
9.5 Fermentation and anaerobic respiration enable cells to
produce ATP without the use of oxygen
9.6 Glycolysis and the citric acid cycle connect to many other metabolic pathways
Chapter 15: Chromosomal Basis of InheritanceAngel Vega
KEY CONCEPTS
15.1 Morgan showed that Mendelian inheritance has its physical
basis in the behavior of chromosomes: Scientific inquiry
15.2 Sex-linked genes exhibit unique patterns of inheritance
15.3 Linked genes tend to be inherited together because they are located near each other on the same chromosome
15.4 Alterations of chromosome number or structure cause
some genetic disorders
15.5 Some inheritance patterns are exceptions to standard
Mendelian inheritance
KEY CONCEPTS
6.1 Biologists use microscopes and the tools of biochemistry to
study cells
6.2 Eukaryotic cells have internal membranes that
compartmentalize their functions
6.3 The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes
6.4 The endomembrane system regulates protein traffic and
performs metabolic functions in the cell
6.5 Mitochondria and chloroplasts change energy from one form to another
6.6 The cytoskeleton is a network of fibers that organizes structures and activities in the cell
6.7 Extracellular components and connections between cells help coordinate cellular activities
KEY CONCEPTS
14.1 Mendel used the scientific approach to identify two laws of inheritance
14.2 Probability laws govern Mendelian inheritance
14.3 Inheritance patterns are often more complex than predicted by simple Mendelian genetics
14.4 Many human traits follow Mendelian patterns of
inheritance
KEY CONCEPTS
5.1 Macromolecules are polymers, built from monomers
5.2 Carbohydrates serve as fuel and building material
5.3 Lipids are a diverse group of hydrophobic molecules
5.4 Proteins include a diversity of structures, resulting in a wide range of functions
5.5 Nucleic acids store, transmit, and help express hereditary
information
5.6 Genomics and proteomics have transformed biological inquiry and applications
This presentation explains the fundamentals of Genetic Code, Protein synthesis mechanism and Antibiotics that inhibits at various stages of Translation.
This PowerPoint is applicable for the medical, paramedical, and all the life science students who read the mechanism of gene expression. This is equally useful for teachers as well. This is the comprehensive coverage on the aforementioned topic.
The following topics are discussed
. Prokaryotic gene expression and regulation
Prokaryotic “gene structure”
The basic structure of Operon
Lactose Operon” regulation
Tryptophan Operon” regulation
2. Eukaryotic gene expression and regulation
Eukaryotic gene structure
Regulons
Gene regulation, History and Evolution , Traditional Methods:
Northern blot
quantitative reverse transcription PCR (qRTPCR)
serial analysis of gene expression(SAGE) and
DNA microarrays.
DNA Chip
Regulation of gene expression in prokaryotes and virusesNOOR ARSHIA
Regulation of gene expression in prokaryotes and viruses includes gene expression mechanism of prokaryotes such as lac operon ,trp operon, feedback inhibition, types of temporal response, positive and negative gene regulation. It also includes mechanisms such as reverse transcriptase in viruses.
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
DERIVATION OF MODIFIED BERNOULLI EQUATION WITH VISCOUS EFFECTS AND TERMINAL V...Wasswaderrick3
In this book, we use conservation of energy techniques on a fluid element to derive the Modified Bernoulli equation of flow with viscous or friction effects. We derive the general equation of flow/ velocity and then from this we derive the Pouiselle flow equation, the transition flow equation and the turbulent flow equation. In the situations where there are no viscous effects , the equation reduces to the Bernoulli equation. From experimental results, we are able to include other terms in the Bernoulli equation. We also look at cases where pressure gradients exist. We use the Modified Bernoulli equation to derive equations of flow rate for pipes of different cross sectional areas connected together. We also extend our techniques of energy conservation to a sphere falling in a viscous medium under the effect of gravity. We demonstrate Stokes equation of terminal velocity and turbulent flow equation. We look at a way of calculating the time taken for a body to fall in a viscous medium. We also look at the general equation of terminal velocity.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Salas, V. (2024) "John of St. Thomas (Poinsot) on the Science of Sacred Theol...Studia Poinsotiana
I Introduction
II Subalternation and Theology
III Theology and Dogmatic Declarations
IV The Mixed Principles of Theology
V Virtual Revelation: The Unity of Theology
VI Theology as a Natural Science
VII Theology’s Certitude
VIII Conclusion
Notes
Bibliography
All the contents are fully attributable to the author, Doctor Victor Salas. Should you wish to get this text republished, get in touch with the author or the editorial committee of the Studia Poinsotiana. Insofar as possible, we will be happy to broker your contact.
Salas, V. (2024) "John of St. Thomas (Poinsot) on the Science of Sacred Theol...
Chapter 18: Gene expression
1. Chapter 18
Regulation of Gene Expression
• Prokaryotes and eukaryotes alter gene
expression in response to their changing
environment
• In multicellular eukaryotes, gene expression
regulates development and is responsible for
differences in cell types
• RNA molecules play many roles in regulating
gene expression in eukaryotes
3. Prokaryotes use Operons: The Basic Concept
• A cluster of functionally related genes can be under
coordinated control by a single on-off “switch”
• The regulatory “switch” is a segment of DNA called an
operator usually positioned within the promoter
• An operon is the entire stretch of DNA that includes the
operator, the promoter, and the genes that they control
• The operon can be switched off by a protein repressor
(some repressors need co-repressors to be active)
• The repressor prevents gene transcription by binding to the
operator and blocking RNA polymerase
• The repressor is the product of a separate regulatory
gene
4. Biosynthetic Operons & Catabolic Operons
• BiosyntheticTryptophan Biosynthesis
– Off when lots of tryptophan (product) around
– Tryptophan molecules act as co-repressor
(activates the repressor protein to turn off the
promoter i.e. block RNA Polymerase)
• CatabolicLactose Utilization
– On when lactose (substrate) is present
– Lactose molecule inactivates the repressor
protein to RNA Polymerase can transcribe
5. Figure 18.3
Promoter
DNA
trpR
Regulatory gene
RNA
polymerase
mRNA
5
3
Protein
Inactive
repressor
mRNA 5
(a) Tryptophan absent, repressor inactive, operon on
DNA
mRNA
Protein Active
repressor
No
RNA
made
Promoter
trp operon
Genes of operon
trpE trpD trpC trpB trpA
Operator
Start codon Stop codon
trpR trpE
Tryptophan
(corepressor)
(b) Tryptophan present, repressor active, operon off
3
5
Polypeptide subunits
that make up enzymes
for tryptophan synthesis
E D C B A
6. Repressible and Inducible Operons: Two Types of
Negative Gene Regulation (= operator+repressor)
• A repressible operon is one that is usually on;
binding of a repressor to the operator shuts off
transcription
• The trp operon is a repressible operon
• An inducible operon is one that is usually off; a
molecule called an inducer inactivates the
repressor and turns on transcription
7. • The lac operon is an inducible operon and
contains genes that code for enzymes used in
the hydrolysis and metabolism of lactose
• By itself, the lac repressor is active and
switches the lac operon off
• A molecule called an inducer inactivates the
repressor to turn the lac operon on
9. • Inducible enzymes usually function in catabolic
pathways; their synthesis is induced by a
chemical signal
• Repressible enzymes usually function in
anabolic pathways; their synthesis is repressed
by high levels of the end product
• Regulation of the trp and lac operons involves
negative control of genes because operons are
switched off by the active form of the repressor
10. Positive Gene Regulation
• Some operons are also subject to positive
control through a stimulatory protein, such as
catabolite activator protein (CAP), an activator
of transcription
• When glucose (a preferred food source of E.
coli) is scarce, CAP is activated by binding with
cyclic AMP
• Activated CAP attaches to the promoter of the
lac operon and increases the affinity of RNA
polymerase, thus accelerating transcription
12. Eukaryotic gene expression :Differential Gene
Expression
• Almost all the cells in an organism are
genetically identical
• Differences between cell types result from
differential gene expression, the expression
of different genes by cells with the same
genome
• Errors in gene expression can lead to diseases
including cancer
• Gene expression is regulated at many stages
13. Figure 18.6 Signal
Chromatin
DNA
Gene available for transcription
RNA Exon
Intron
Cap
Primary
transcript
Tail
mRNA in nucleus
NUCLEUS
Transcription
RNA processing
Transport to
cytoplasm
Chromatin
modification:
DNA unpacking
CYTOPLASM
mRNA in cytoplasm
TranslationDegradation
of mRNA
Polypeptide
Protein processing
Active protein
Degradation
of protein
Transport to cellular
destination
Cellular function
(such as enzymatic
activity or structural
support)
Many places to
regulate: review
examples at
each box with
your neighbor
14. Regulation of Chromatin Structure
• Genes within highly packed heterochromatin
are usually not expressed e.g. Barr Body
• Chemical modifications to histones and DNA of
chromatin influence both chromatin structure
and gene expression
15. Overview: How Eukaryotic Genomes Work and
Evolve
• Two features of eukaryotic genomes are a major
information-processing challenge:
– First, the typical eukaryotic genome is much
larger than that of a prokaryotic cell
– Second, cell specialization limits the
expression of many genes to specific cells
• The DNA-protein complex, called chromatin, is
ordered into higher structural levels than the DNA-
protein complex in prokaryotes
16. LE 19-2a
DNA double helix
Histone
tails
His-
tones
Linker DNA
(“string”)
Nucleosome
(“bead”)
10 nm
2 nm
Histone H1
Nucleosomes (10-nm fiber)
Level 1
18. LE 19-2c
300 nm
Loops
Scaffold
Protein scaffold
Looped domains (300-nm fiber)
In turn, the 30-nm fiber forms looped domains,
making up a 300-nm fiber
Level 3
19. LE 19-2d
Metaphase chromosome
700 nm
1,400 nm
In a mitotic chromosome, the looped domains coil and
fold, forming the metaphase chromosome
Level 4
Level 5
20. • Interphase chromatin is usually much less
condensed than that of mitotic chromosomes
• Much of the interphase chromatin is present as a
10-nm fiber, and some is 30-nm fiber, which in
some regions is folded into looped domains
• Interphase chromosomes have highly condensed
areas, called heterochromatin, and less
compacted areas, called euchromatin
21. Histone Modifications
• In histone acetylation, acetyl groups are
attached to positively charged lysines in
histone tails
• This process loosens chromatin structure,
thereby promoting the initiation of transcription
• The addition of methyl groups (methylation)
can condense chromatin; the addition of
phosphate groups (phosphorylation) next to a
methylated amino acid can loosen chromatin
22. Fig. 18-7
Histone
tails
DNA
double helix
(a) Histone tails protrude outward from a
nucleosome
Acetylated histones
Amino
acids
available
for chemical
modification
(b) Acetylation of histone tails promotes loose
chromatin structure that permits transcription
Unacetylated histones
23. DNA Methylation
• DNA methylation, the addition of methyl groups
to certain bases in DNA, is associated with
reduced transcription in some species
• DNA methylation can cause long-term
inactivation of genes in cellular differentiation
• In genomic imprinting, methylation regulates
expression of either the maternal or paternal
alleles of certain genes at the start of
development When passed to next generation,
it is called??
24. DNA Methylation
• DNA methylation, the addition of methyl groups
to certain bases in DNA, is associated with
reduced transcription in some species
• DNA methylation can cause long-term
inactivation of genes in cellular differentiation
• In genomic imprinting, methylation regulates
expression of either the maternal or paternal
alleles of certain genes at the start of
development When passed to next generation,
it is called?? Epigenetic
25. Organization of a Typical Eukaryotic Gene
• Associated with most eukaryotic genes are
control elements, segments of noncoding
DNA that help regulate transcription by binding
certain proteins
• Control elements and the proteins they bind
are critical to the precise regulation of gene
expression in different cell types
26. Figure 18.8
Enhancer (group of
distal control elements)
Proximal
control elements
Transcription
start site
Promoter
Exon
ExonPrimary RNA
transcript
(pre-mRNA)
Intron
Intron
Exon
Exon
Intron
Intron
Exon
Exon
Poly-A signal
sequence
Transcription
termination
region
Downstream
Poly-A
signal
Cleaved 3′ end
of primary
transcript
5′
3′
Transcription
Upstream
DNA
Intron RNA
RNA processing
Coding segment
Start
codon
Stop
codon 3′ UTR Poly-A
tail
AAA⋯AAAmRNA
5′ Cap 5′ UTR
G P P P
27. The Roles of Transcription Factors
• To initiate transcription, eukaryotic RNA
polymerase requires the assistance of proteins
called transcription factors
• General transcription factors are essential for
the transcription of all protein-coding genes
and bind to the promoter region
• In eukaryotes, high levels of transcription of
particular genes depend on control elements
interacting with specific transcription factors
28. • Proximal control elements are located close to
the promoter
• Distal control elements, groups of which are
called enhancers, may be far away from a
gene or even located in an intron
Enhancers and Specific Transcription Factors
29. Figure 18.10-3
DNA Activators Promoter
Enhancer Distal control
element
TATA
box
Gene
DNA-
bending
protein
Group of mediator proteins
General
transcription
factors
RNA
polymerase II
RNA polymerase II
RNA synthesis
Transcription
initiation complex
30. • An activator is a protein that binds to an enhancer
and stimulates transcription of a gene
• Bound activators cause mediator proteins to
interact with proteins at the promoter
Combinatorial Control of Gene Activation
• A particular combination of control elements can
activate transcription only when the appropriate
activator proteins are present
32. • Some transcription factors function as
repressors, inhibiting expression of a particular
gene
• Some activators and repressors act indirectly
by influencing chromatin structure to promote
or silence transcription
33. Coordinately Controlled Genes in Eukaryotes
• Unlike the genes of a prokaryotic operon, each
of the coordinately controlled eukaryotic genes
has a promoter and control elements
• These genes can be scattered over different
chromosomes, but each has the same
combination of control elements
• Copies of the activators recognize specific
control elements and promote simultaneous
transcription of the genes
34. Nuclear Architecture and Gene Expression
• Loops of chromatin extend from individual
chromosome territories into specific sites in the
nucleus
• Loops from different chromosomes may
congregate at particular sites, some of which are
rich in transcription factors and RNA polymerases
• These may be areas specialized for a common
function
35. Exons
RNA splicing
1 2 3 4 5
1 2 3 4 5
1 2 3 5 1 2 4 5OR
Troponin T gene
DNA
Primary
RNA
transcript
mRNA
alternative RNA splicing, different mRNA molecules are produced from the same
primary transcript, depending on which RNA segments are treated as exons and
which as introns
36. RNA turnover
Protein turnover (shown here)
Proteasome
and ubiquitin
to be recycledProteasome
Protein
fragments
(peptides)Protein entering a
proteasome
Ubiquitinated
protein
Protein to
be degraded
Ubiquitin
37. Concept 18.3: Noncoding RNAs play multiple roles
in controlling gene expression
• Only a small fraction of DNA codes for
proteins, rRNA, and tRNA
• A significant amount of the genome may be
transcribed into noncoding RNAs
• Noncoding RNAs regulate gene expression at
two points: mRNA translation and chromatin
configuration
38. Effects on mRNAs by MicroRNAs and Small
Interfering RNAs
• MicroRNAs (miRNAs) are small single-
stranded RNA molecules that can bind to
mRNA
• These can degrade mRNA or block its
translation
39. Figure 18.14 also called siRNA
for silencing RNAor small
interfering RNA
miRNA
miRNA-
protein
complex
The miRNA binds
to a target mRNA.
mRNA degraded Translation blocked
OR
If bases are completely complementary, mRNA is degraded.
If match is less than complete, translation is blocked.
1
2
40. • The phenomenon of inhibition of gene
expression by RNA molecules is called RNA
interference (RNAi)
• RNAi is caused by small interfering RNAs
(siRNAs)
• RNAi is used in the laboratory as a means
of disabling genes to investigate their
function
• siRNAs and miRNAs are similar but form from
different RNA precursors
41. Chromatin Remodeling and Silencing of
Transcription by Small RNAs
• siRNAs play a role in heterochromatin
formation and can block large regions of the
chromosome
• Small RNAs may also block transcription of
specific genes
42. Figure 18.15. In some yeasts siRNAs re-form heterochromatin at centromeres after
chromosome replication
RNA transcripts (red) produced.
Yeast enzyme synthesizes strands
complementary to RNA transcripts.
Double-stranded RNA processed into
siRNAs that associate with proteins.
The siRNA-protein complexes recruit
histone-modifying enzymes.
The siRNA-protein complexes bind
RNA transcripts and become tethered
to centromere region.
Chromatin condensation is initiated
and heterochromatin is formed.
1
2
3
4
5
6
Centromeric DNA
RNA polymerase
RNA transcript
Sister chromatids
(two DNA
molecules)
siRNA-protein
complex
Centromeric DNA
Chromatin-
modifying
enzymes
Heterochromatin at
the centromere region
43. Fig. 18-UN5
Chromatin modification
RNA processing
TranslationmRNA
degradation
Protein processing
and degradation
mRNA degradation
• miRNA or siRNA can target specific mRNAs
for destruction.
• miRNA or siRNA can block the translation
of specific mRNAs.
Transcription
• Small RNAs can promote the formation of
heterochromatin in certain regions, blocking
transcription.
Chromatin modification
Translation
44. Summary
• Genes in highly compacted
chromatin are generally not
transcribed.
Chromatin modification
• DNA methylation generally
reduces transcription.
• Histone acetylation seems to
loosen chromatin structure,
enhancing transcription.
Chromatin modification
Transcription
RNA processing
TranslationmRNA
degradation
Protein processing
and degradation
mRNA degradation
• Each mRNA has a
characteristic life span,
determined in part by
sequences in the 5 and
3 UTRs.
• Protein processing and
degradation by proteasomes
are subject to regulation.
Protein processing and degradation
• Initiation of translation can be controlled
via regulation of initiation factors.
Translation
ormRNA
Primary RNA
transcript
• Alternative RNA splicing:
RNA processing
• Coordinate regulation:
Enhancer for
liver-specific genes
Enhancer for
lens-specific genes
Bending of the DNA enables activators to
contact proteins at the promoter, initiating
transcription.
Transcription
• Regulation of transcription initiation:
DNA control elements bind specific
transcription factors.
45. Concept 18.4: A program of differential gene
expression leads to the different cell types in a
multicellular organism
• During embryonic development, a fertilized egg
gives rise to many different cell types
• Cell types are organized successively into
tissues, organs, organ systems, and the whole
organism
• Gene expression orchestrates the
developmental programs of animals
46. • Cell differentiation is the process by which
cells become specialized in structure and
function
• The physical processes that give an organism
its shape constitute morphogenesis
• Differential gene expression results from genes
being regulated differently in each cell type
• Materials in the egg can set up gene regulation
that is carried out as cells divide
47. Concept 18.5: Cancer results from genetic changes
that affect cell cycle control
• The gene regulation systems that go wrong
during cancer are the very same systems
involved in embryonic development
• Cancer can be caused by mutations to genes
that regulate cell growth and division
• Tumor viruses can cause cancer in animals
including humans
48. Oncogenes and Proto-Oncogenes
• Oncogenes are cancer-causing genes
• Proto-oncogenes are the corresponding
normal cellular genes that are responsible for
normal cell growth and division
• Conversion of a proto-oncogene to an
oncogene can lead to abnormal stimulation of
the cell cycle
49. • Proto-oncogenes can be converted to
oncogenes by
– Movement of DNA within the genome: if it ends
up near an active promoter, transcription may
increase
– Amplification of a proto-oncogene: increases
the number of copies of the gene
– Point mutations in the proto-oncogene or its
control elements: cause an increase in gene
expression
50. Figure 18.23
Proto-oncogene Proto-oncogene Proto-oncogene
Point mutation:Gene amplification:
multiple copies of
the gene
Translocation or
transposition: gene
moved to new locus,
under new controls
New promoter
Oncogene Oncogene Oncogene
within the gene
within a control
element
Normal growth-
stimulating
protein in excess
Normal growth-stimulating
protein in excess
Normal growth-
stimulating protein
in excess
Hyperactive or
degradation-
resistant
protein
51. Tumor-Suppressor Genes
• Tumor-suppressor genes help prevent
uncontrolled cell growth
• Mutations that decrease protein products of
tumor-suppressor genes may contribute to
cancer onset
• Tumor-suppressor proteins
– Repair damaged DNA
– Control cell adhesion
– Inhibit the cell cycle in the cell-signaling
pathway
52. Interference with Normal Cell-Signaling Pathways
• Mutations in the ras proto-oncogene and p53
tumor-suppressor gene are common in human
cancers
• Mutations in the ras gene can lead to
production of a hyperactive Ras protein and
increased cell division
53. Figure 18.24
G protein
Growth factor
Receptor Protein
kinases
Transcription
factor (activator)
NUCLEUS Protein that
stimulates
the cell cycle
Transcription
factor (activator)
NUCLEUS
Overexpression
of protein
Ras
Ras
MUTATION
GTP
GTP
Ras protein active
with or without
growth factor.
P P
P P
P P
1
3
2
5
4
6
54. • Suppression of the cell cycle can be important
in the case of damage to a cell’s DNA; p53
prevents a cell from passing on mutations due
to DNA damage
• Mutations in the p53 gene prevent suppression of
the cell cycle
55. Figure 18.25
Protein kinases
DNA damage
in genome
Active form
of p53
Transcription
DNA damage
in genome
UV
light
UV
light
Defective or
missing
transcription
factor.
Inhibitory
protein
absent
Protein that
inhibits the
cell cycleNUCLEUS
MUTATION
1 3 4
2
5
56. The Multistep Model of Cancer Development
• Multiple mutations are generally needed for
full-fledged cancer; thus the incidence
increases with age
• At the DNA level, a cancerous cell is usually
characterized by at least one active oncogene
and the mutation of several tumor-suppressor
genes
57. Figure 18.26a
1
Colon wall
Loss of tumor-
suppressor gene
APC (or other)
Normal colon
epithelial cells
2
3
4
5
Activation of
ras oncogene
Additional
mutations
Loss of tumor-
suppressor
gene SMAD4
Larger benign
growth (adenoma)
Malignant tumor
(carcinoma)
Small benign
growth (polyp)
Loss of
tumor-suppressor
gene p53
58. Inherited Predisposition and Other Factors
Contributing to Cancer
• Individuals can inherit oncogenes or mutant
alleles of tumor-suppressor genes
• Inherited mutations in the tumor-suppressor
gene adenomatous polyposis coli are common
in individuals with colorectal cancer
• Mutations in the BRCA1 or BRCA2 gene are
found in at least half of inherited breast cancers
59. You should now be able to:
1. Explain the concept of an operon and the function of the operator, repressor, and corepressor
2. Explain the adaptive advantage of grouping bacterial genes into an operon
3. Explain how repressible and inducible operons differ and how those differences reflect differences
in the pathways they control
4. Explain how DNA methylation and histone acetylation affect chromatin structure and the regulation
of transcription
5. Define control elements and explain how they influence transcription in eukaryotes
6. Explain the role of promoters, enhancers, activators, and repressors in transcription control
7. Explain how eukaryotic genes can be coordinately expressed
8. Describe the roles played by small RNAs on gene expression
9. Describe two sources of information that instruct a cell to express genes at the appropriate time
10. Explain how mutations in tumor-suppressor genes can contribute to cancer
11. Describe the effects of mutations to the p53 and ras genes