The document discusses DNA transcription in prokaryotes and eukaryotes. It defines transcription as the synthesis of RNA from a DNA template. In eukaryotes, transcription occurs in the nucleus and involves RNA polymerases I, II, and III. The process includes initiation, elongation, and termination. Eukaryotic transcription is more complex than prokaryotic transcription due to larger genome size, chromatin structure, and presence of regulatory elements. The primary transcript in eukaryotes undergoes processing before becoming a mature mRNA.
Transcription definition
steps of transcription
general structure of gene
RNA polymerase structure
Transcription in prokaryotes in detail (initiation, elongation and termination)
Transcription and the various stages of transcriptionMohit Adhikary
Transcription and its stages, the enzymes involved, the steps of transcription, the regulators of transcription, post translation modifications, formation of the types of RNA, applied concept
difference between Transcription in eukaryotes and prokaryotes kamilKhan63
In prokaryotes the transcription is simple while in eukaryotes the transcription is complicated or complex.
Occurrences
Prokaryotic transcription occurs in cytoplasm.
Eukaryotic transcription occurs in nucleus.
3. In prokaryotes mRNA is transcribed directly from the template DNA strand while in eukaryotes 1st pre-mRNA is formed and then processed to yield mature mRNA.
MOLECULAR GENETICS : PROKARYOTIC TRANSCRIPTION OR RNA SYNTHESIS BY DNA DEPEN...Amritha S R
The process of conversion of DNA to RNA or genome to transcriptome is called transcription. Central dogma of life or molecular biology both with pre-bioinformatics era & bioinformatics era is shown in flow chart. All the 3 stages of transcription i.e; initiation, elongation & termination are explained in this presentation. Information regarding DNA dependent RNA polymarase along with core enzyme & sigma factor is given in pictorial representation. The promoter sequence, hair-pin loop, Rho factor dependent & independent termination of transcription,post transcriptional modification of prokaryotic transcription before entering translation is also explained in detail.
Transcription definition
steps of transcription
general structure of gene
RNA polymerase structure
Transcription in prokaryotes in detail (initiation, elongation and termination)
Transcription and the various stages of transcriptionMohit Adhikary
Transcription and its stages, the enzymes involved, the steps of transcription, the regulators of transcription, post translation modifications, formation of the types of RNA, applied concept
difference between Transcription in eukaryotes and prokaryotes kamilKhan63
In prokaryotes the transcription is simple while in eukaryotes the transcription is complicated or complex.
Occurrences
Prokaryotic transcription occurs in cytoplasm.
Eukaryotic transcription occurs in nucleus.
3. In prokaryotes mRNA is transcribed directly from the template DNA strand while in eukaryotes 1st pre-mRNA is formed and then processed to yield mature mRNA.
MOLECULAR GENETICS : PROKARYOTIC TRANSCRIPTION OR RNA SYNTHESIS BY DNA DEPEN...Amritha S R
The process of conversion of DNA to RNA or genome to transcriptome is called transcription. Central dogma of life or molecular biology both with pre-bioinformatics era & bioinformatics era is shown in flow chart. All the 3 stages of transcription i.e; initiation, elongation & termination are explained in this presentation. Information regarding DNA dependent RNA polymarase along with core enzyme & sigma factor is given in pictorial representation. The promoter sequence, hair-pin loop, Rho factor dependent & independent termination of transcription,post transcriptional modification of prokaryotic transcription before entering translation is also explained in detail.
RNA Polymerase
Introduction
Purification
History
PRODUCTS OF RNAP
Messenger RNA
Non-coding RNA or "RNA genes
Transfer RNA
Ribosomal RNA
Micro RNA
Catalytic RNA (Ribozyme)
prokaryotic and eukaryotic
Transcription by RNA Polymerase
TYPES OF RNA POLYMERASE
Type I
Type II
Type III
Prokaryotic Transcription Unit
EXPRESSION OF A PROKARYOTIC GENE
Prokaryotic Polycistronic Message Codes for Several Different Proteins
Eukaryotic Transcription Unit
ENHANCERS AND SILENCERS
RESULT OF THE TRANSCRIPTION CYCLE
RNAP III TRANSCRIBES HUMAN MICRORNAS
RNAP I–specific subunits promotepolymerase clustering to enhance the rRNA genetranscription cycle
RNAP II–TFIIB STRUCTURE ANDMECHANISM OF TRANSCRIPTION INITIATION
FIVE CHECKPOINTS MAINTAINING THE FIDELITY OFTRANSCRIPTION BY RNAP IN STRUCTURAL ANDENERGETIC DETAILS
RNA Polymerase
Introduction
Purification
History
PRODUCTS OF RNAP
Messenger RNA
Non-coding RNA or "RNA genes
Transfer RNA
Ribosomal RNA
Micro RNA
Catalytic RNA (Ribozyme)
prokaryotic and eukaryotic
Transcription by RNA Polymerase
TYPES OF RNA POLYMERASE
Type I
Type II
Type III
Prokaryotic Transcription Unit
EXPRESSION OF A PROKARYOTIC GENE
Prokaryotic Polycistronic Message Codes for Several Different Proteins
Eukaryotic Transcription Unit
ENHANCERS AND SILENCERS
RESULT OF THE TRANSCRIPTION CYCLE
RNAP III TRANSCRIBES HUMAN MICRORNAS
RNAP I–specific subunits promotepolymerase clustering to enhance the rRNA genetranscription cycle
RNAP II–TFIIB STRUCTURE ANDMECHANISM OF TRANSCRIPTION INITIATION
FIVE CHECKPOINTS MAINTAINING THE FIDELITY OFTRANSCRIPTION BY RNAP IN STRUCTURAL ANDENERGETIC DETAILS
Protein synthesis is the process whereby biological cells generate new proteins. Translation, the assembly of amino acids by ribosomes, is an essential part of the biosynthetic pathway, along with generation of messenger RNA (mRNA), aminoacylation of transfer RNA (tRNA), co-translational transport, and post-translational modification. Protein biosynthesis is strictly regulated at multiple steps. They are principally during transcription (phenomenon of RNA synthesis from DNA template) and translation (phenomenon of amino acid assembly from RNA). The cistron DNA is transcribed into the first of a series of RNA intermediates. The last version is used as a template in synthesis of a polypeptide chain. Protein will often be synthesized directly from genes by translating mRNA. A proprotein is an inactive protein containing one or more inhibitory peptides that can be activated when the inhibitory sequence is removed by proteolysis during post translational modification. A preprotein is a form that contains a signal sequence (an N-terminal signal peptide) that specifies its insertion into or through membranes, i.e., targets them for secretion. The signal peptide is cleaved off in the endoplasmic reticulum. Preproteins have both sequences (inhibitory and signal) still present. In protein synthesis, a succession of tRNA molecules charged with appropriate amino acids are brought together with an mRNA molecule and matched up by base-pairing through the anti-codons of the tRNA with successive codons of the mRNA. The amino acids are then linked together to extend the growing protein chain, and the tRNAs, no longer carrying amino acids, are released. This whole complex of processes is carried out by the ribosome, formed of two main chains of RNA, called ribosomal RNA (rRNA), and more than 50 different proteins. The ribosome latches onto the end of an mRNA molecule and moves along it, capturing loaded tRNA molecules and joining together their amino acids to form a new protein chain.
This presentation explains DNA transcription and RNA Processing.
It gives details about prokaryotic DNA transcription and eukaryotic DNA transcription. it also explains post-transcriptional modification both in prokaryotes and eukaryotes.
Photosystem II captures and transfers energy.
– chlorophyll absorbs
energy from sunlight
– energized electrons
enter electron
transport chain
– water molecules are
split
– oxygen is released as
waste
– hydrogen ions are
transported across
thylakoid membrane
4.1 Chemical Energy and ATP
• Photosystem I captures energy and produces energycarrying molecules.
– chlorophyll absorbs
energy from sunlight
– energized electrons
are used to make
NADPH
– NADPH is transferred
to light-independent
reactions
4.1 Chemical Energy and ATP
• The light-dependent reactions produce ATP.
– hydrogen ions flow through a channel in the thylakoid
membrane
– ATP synthase attached to the channel makes ATP
4.1 Chemical Energy and ATP
• Light-independent
reactions occur in the
stroma and use CO2
molecules.
The second stage of photosynthesis uses energy from
the first stage to make sugars.
4.1 Chemical Energy and ATP
• A molecule of glucose is formed as it stores some of the
energy captured from sunlight.
– carbon dioxide molecules enter the Calvin Photosystem II captures and transfers energy.
– chlorophyll absorbs
energy from sunlight
– energized electrons
enter electron
transport chain
– water molecules are
split
– oxygen is released as
waste
– hydrogen ions are
transported across
thylakoid membrane
4.1 Chemical Energy and ATP
• Photosystem I captures energy and produces energycarrying molecules.
– chlorophyll absorbs
energy from sunlight
– energized electrons
are used to make
NADPH
– NADPH is transferred
to light-independent
reactions
4.1 Chemical Energy and ATP
• The light-dependent reactions produce ATP.
– hydrogen ions flow through a channel in the thylakoid
membrane
– ATP synthase attached to the channel makes ATP
4.1 Chemical Energy and ATP
• Light-independent
reactions occur in the
stroma and use CO2
molecules.
The second stage of photosynthesis uses energy from
the first stage to make sugars.
4.1 Chemical Energy and ATP
• A molecule of glucose is formed as it stores some of the
energy captured from sunlight.
– carbon dioxide molecules enter the Calvin Photosystem II captures and transfers energy.
– chlorophyll absorbs
energy from sunlight
– energized electrons
enter electron
transport chain
– water molecules are
split
– oxygen is released as
waste
– hydrogen ions are
transported across
thylakoid membrane
4.1 Chemical Energy and ATP
• Photosystem I captures energy and produces energycarrying molecules.
– chlorophyll absorbs
energy from sunlight
– energized electrons
are used to make
NADPH
– NADPH is transferred
to light-independent
reactions
4.1 Chemical Energy and ATP
• The light-dependent reactions produce ATP.
– hydrogen ions flow through a channel in the thylakoid
membrane
– ATP synthase attached to the channel makes ATP
4.1 Chemical Energy and ATP
• Light-independent
reactions occur in the
stroma and use CO2
molecules.
The second stage of photosynthesis uses energy frvf
Prokaryotes are organisms that consist of a single prokaryotic cell. Eukaryotic cells are found in plants, animals, fungi, and protists. They range from 10–100 μm in diameter, and their DNA is contained within a membrane-bound nucleus.Prokaryotes do not have membrane-enclosed nuclei. Therefore, the processes of transcription, translation, and mRNA degradation can all occur simultaneously.
The process by which an RNA copy of a gene is made or it’s a DNA dependent RNA synthesis.
Transcription resembles replication
In its fundamental chemical mechanism
Its polarity (direction of synthesis)
Its use of a template
Transcription differs from replication
It does not requires a primer
It involves only limited segments of a DNA molecule
Within transcribed segments only one DNA strand serves as a template for synthesis of RNA.
Transcription and synthesis of different RNAs
Processing of RNA transcript
Catalytic RNA
RNA splicing and Spliceosome
Transport of RNA through nuclear pore
Translation and polypeptide synthesis
Posttranslational modification
Protein trafficking and degradation
Antibiotics and inhibition of protein synthesis.
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
- BEYOND BORDERS: GLOBAL INITIATIVES FOR DEMOCRATIZING LIFE SCIENCE TECHNOLOGIES AND PROMOTING ACCESS TO HEALTHCARE
- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
2. • The synthesis of an RNA molecule from DNA is
called Transcription.
• All eukaryotic cells have five major classes of RNA:
ribosomal RNA (rRNA), messenger RNA (mRNA),
transfer RNA (tRNA), small nuclear RNA and microRNA
(snRNA and miRNA).
• The first three are involved in protein synthesis, while
the small RNAs are involved in mRNA splicing and
regulation of gene expression.
3. Similarities between Replication andSimilarities between Replication and
TranscriptionTranscription
The processes of DNA and
RNA synthesis are similar in
that they involve-
(1) the general steps of
initiation, elongation, and
termination with 5' to 3'
polarity;
(2) large, multicomponent
initiation complexes; and
(3) adherence to Watson-Crick
base-pairing rules.
4. Differences between Replication andDifferences between Replication and
TranscriptionTranscription
(1) Ribonucleotides are used in RNA synthesis rather
than deoxy ribonucleotides;
(2) U replaces T as the complementary base pair for A in
RNA;
(3) A primer is not involved in RNA synthesis;
(4) Only a portion of the genome is transcribed or
copied into RNA, whereas the entire genome must be
copied during DNA replication; and
(5) There is no proofreading function during RNA
transcription.
5. Template strandTemplate strand
The strand that is transcribed or copied into an RNA
molecule is referred to as the template strand of the DNA.
The other DNA strand, the non-template strand, is
frequently referred to as the coding strand of that gene.
6. Template strandTemplate strand
With the exception of T for U changes, coding
strand corresponds exactly to the sequence of the
RNA primary transcript, which encodes the
(protein) product of the gene.
7. Transcription unitTranscription unit
• A transcription unit is defined as that region of DNA
that includes the signals for transcription initiation,
elongation, and termination.
• DNA-dependent RNA polymerase is the enzyme
responsible for the polymerization of ribonucleotides into
a sequence complementary to the template strand of the
gene.
• The enzyme attaches at a specific site—the promoter—
on the template strand.
• This is followed by initiation of RNA synthesis at the
starting point, and the process continues until a
termination sequence is reached.
9. Primary transcriptPrimary transcript
• The RNA product, which is synthesized in the 5' to 3'
direction, is the primary transcript.
• In prokaryotes, this can represent the product of
several contiguous genes
• In mammalian cells, it usually represents the product
of a single gene
• The 5' terminals of the primary RNA transcript and
the mature cytoplasmic RNA are identical.
• The starting point of transcription corresponds
to the 5' nucleotide of the mRNA.
10. • This is designated position +1, as is the corresponding
nucleotide in the DNA
• The numbers increase as the sequence
proceeds downstream.
• The nucleotide in the promoter adjacent to the
transcription initiation site is designated -1,
• These negative numbers increase as the sequence
proceeds upstream, away from the initiation site.
• This provides a conventional way of defining the
location of regulatory elements in the promoter.
Primary transcriptPrimary transcript
12. Bacterial DNA-Dependent RNA PolymeraseBacterial DNA-Dependent RNA Polymerase
The DNA-dependent RNA
polymerase (RNAP) of the
bacterium Escherichia coli exists as
an approximately 400 kDa core
complex consisting of-
• two identical α subunits,
• similar but not identical β and β '
subunits, and
• an ω subunit and a
• A sigma subunit (σ)
• Beta is thought to be the catalytic
subunit.
13. Mammalian DNA-Dependent RNA PolymerasesMammalian DNA-Dependent RNA Polymerases
Mammalian cells possess three distinct nuclear DNA-
Dependent RNA Polymerases
RNA polymerase I is for the synthesis of r RNA
RNA polymerase II is for the synthesis of m RNA and
miRNA
RNA polymerase III is for the synthesis of tRNA/5S
rRNA, snRNA
14. Steps of RNA Synthesis-
The process of transcription of a typical gene of E. Coli
can be divided in to three phases-
i) Initiation
ii) Elongation
iii) Termination
Prokaryotic transcriptionProkaryotic transcription
15. • Initiation of transcription involves the binding of the RNA
polymerase holoenzyme to the promoter region on the
DNA to form a preinitiation complex, or PIC
• Characteristic "Consensus" nucleotide sequence of the
prokaryotic promoter region are highly conserved.
Initiation of TranscriptionInitiation of Transcription
16. Pribnow box
This is a stretch of 6 nucleotides
( 5'- TATAAT-3') centered about 8-
10 nucleotides to the left of the
transcription start site.
-35 Sequence
A second consensus nucleotide
sequence ( 5'- TTGACA-3'), is
centered about 35 bases to the
left of the transcription start site.
Structure of bacterial prokaryotic promoterStructure of bacterial prokaryotic promoter
regionregion
17. Initiation of TranscriptionInitiation of Transcription
• Binding of RNA-polymerase (RNAP) to the promoter
region is followed by a conformational change of the
RNAP, and the first nucleotide (almost always a
purine) then associates with the initiation site on the
subunit of the enzyme.
• In the presence of the appropriate nucleotide, RNAP
catalyzes the formation of a phosphodiester bond,
and the nascent chain is now attached to the
polymerization site on the subunit of RNAP.
18. Initiation of Transcription (contd.)Initiation of Transcription (contd.)
• In both prokaryotes and eukaryotes, a purine
ribonucleotide is usually the first to be polymerized
into the RNA molecule.
• After 10–20 nucleotides have been polymerized, RNAP
undergoes a second conformational change leading
to promoter clearance.
• Once this transition occurs, RNAP physically moves
away from the promoter, transcribing down the
transcription unit, leading to the next phase of the
process, elongation.
21. • As the elongation complex containing the core RNA
polymerase progresses along the DNA molecule, DNA
unwinding must occur in order to provide access for
the appropriate base pairing to the nucleotides of the
template strand.
• The extent of this transcription bubble (i.e., DNA
unwinding) is constant throughout and is about 20
base pairs.
Elongation step of TranscriptionElongation step of Transcription
22.
23. Elongation step of TranscriptionElongation step of Transcription
RNA polymerase has
associated with it an
"unwindase" activity that
opens the DNA helix.
Topo isomerase both
precedes and follows the
progressing RNAP to
prevent the formation of
super helical complexes.
Base pairing rule is
followed during the
incorporation of
ribonucleotides
24.
25. Termination of transcriptionTermination of transcription
Termination of the synthesis of the RNA molecule in
bacteria is of two types-
Rho (ρ) dependent termination-
• The termination process is signaled by a sequence in
the template strand of the DNA molecule—a signal
that is recognized by a termination protein, the rho
(ρ) factor.
• Rho is an ATP-dependent RNA-stimulated helicase
that disrupts the nascent RNA-DNA complex.
26.
27. Termination of transcription (contd.)Termination of transcription (contd.)
b) Rho independent termination
• This process requires the presence of intrachain self
complementary sequences in the newly formed
primary transcript so that it can acquire a stable hair
pin turn that slows down the progress of the RNA
polymerase and causes it to pause temporarily.
• Near the stem of the hairpin, a sequence occurs that
is rich in G and C.
• This stabilizes the secondary structure of the hair pin.
28. Termination of transcription (contd.)Termination of transcription (contd.)
•Beyond the hair
pin, the RNA
transcript contains a
strings of Us, the
bonding of Us to the
corresponding As is
weak.
•This facilitates the
dissociation of the
primary transcript
from DNA.
29.
30. Termination of transcription (contd.)Termination of transcription (contd.)
After termination of synthesis of the RNA molecule,
the enzyme separates from the DNA template.
With the assistance of another factor, the core
enzyme then recognizes a promoter at which the
synthesis of a new RNA molecule commences.
31.
32. Eukaryotic transcriptionEukaryotic transcription
• The general process of transcription can be applied to
both prokaryotic cells and eukaryotic cells.
• The basic biochemistry for each is the same; however,
the specific mechanisms and regulation of
transcription differ between prokaryotes and
eukaryotes.
• Transcription of eukaryotic genes is far more a
complicated process than prokaryotes.
33. Prokaryotic versus EukaryoticProkaryotic versus Eukaryotic
TranscriptionTranscription
1) Location
In prokaryotes (bacteria), transcription occurs in the
cytoplasm.
Translation of the mRNA into proteins also occurs in
the cytoplasm
34. Prokaryotic versus EukaryoticProkaryotic versus Eukaryotic
TranscriptionTranscription
In eukaryotes,
transcription occurs in the
cell's nucleus, mRNA then
moves to the cytoplasm for
translation.
35. Prokaryotic versus Eukaryotic TranscriptionProkaryotic versus Eukaryotic Transcription
2) Genome size
The genome size is much larger in eukaryotes,
Greater specificity is needed for the transcription of
eukaryotic genes.
36. Prokaryotic versus Eukaryotic TranscriptionProkaryotic versus Eukaryotic Transcription
3) Chromatin Structure
DNA in prokaryotes is much more
accessible to RNA polymerase than
DNA in eukaryotes.
Eukaryotic DNA is wrapped around
proteins called histones to form
structures called nucleosomes
Eukaryotic DNA is packed to form
chromatin .
While RNA polymerase interacts
directly with prokaryotic DNA, other
proteins mediate the interaction
between RNA polymerase and DNA
in eukaryotes
37. Prokaryotic versus Eukaryotic TranscriptionProkaryotic versus Eukaryotic Transcription
4) RNA polymerases
• There are three distinct classes of RNA polymerases in
eukaryotic cells. All are large enzymes with multiple
subunits. Each class of RNA polymerase recognizes
particular types of genes.
• RNA polymerase I- Synthesizes the precursor of the large
ribosomal RNAs (28S, 18S and 5.8S).
• RNA polymerase II - Synthesizes the precursors of
messenger RNA and small nuclear RNAs(snRNAs).
• RNA polymerase III- Synthesizes small RNA, including t
RNAs, small 5S RNA and some snRNAs.
38. Prokaryotic versus Eukaryotic TranscriptionProkaryotic versus Eukaryotic Transcription
5) Promoter regions
• Eukaryotic promoters are more complex.
• Two types of sequence elements are promoter-proximal
and distal regulatory elements.
• There are two elements in promoter proximal ,One of
these defines where transcription is to
commence along the DNA, and the other contributes to
the mechanisms that control how frequently this event is
to occur.
• Most mammalian genes have a TATA box that is usually
located 25–30 bp upstream from the transcription start
site.
39.
40. Prokaryotic versus Eukaryotic TranscriptionProkaryotic versus Eukaryotic Transcription
6) Promoter identification
• In contrast to the situation in prokaryotes, eukaryotic
RNA polymerases alone are not able to discriminate
between promoter sequences and other regions of
DNA
• The TATA box is bound by 34 kDa TATA binding
protein (TBP), which in turn binds several other
proteins called TBP-associated factors (TAFs).
• This complex of TBP and TAFs is referred to as TFIID
41.
42. Prokaryotic versus Eukaryotic TranscriptionProkaryotic versus Eukaryotic Transcription
Binding of TFIID to the TATA box sequence is
thought to represent the first step in the formation of
the transcription complex on the promoter.
Another set of proteins—co activators—help regulate
the rate of transcription initiation by interacting with
transcription activators that bind to upstream DNA
elements
43. Prokaryotic versus Eukaryotic TranscriptionProkaryotic versus Eukaryotic Transcription
7) Enhancers and Repressors
A third class of sequence elements can either increase
or decrease the rate of transcription initiation of
eukaryotic genes
These elements are called either enhancers or
repressors (or silencers), depending on which effect
they have.
44.
45. Prokaryotic versus EukaryoticProkaryotic versus Eukaryotic
TranscriptionTranscription
Processing of primary transcript
• mRNA produced as a result of transcription is not
modified in prokaryotic cells. Eukaryotic cells modify
mRNA by RNA splicing, 5' end capping, and addition
of a polyA tail.
• Most eukaryotic RNAs are synthesized as precursors
that contain excess sequences which are removed
prior to the generation of mature, functional RNA.