RNA splicing, in molecular biology, is a form of RNA processing in which a newly made precursor messenger RNA transcript is transformed into a mature messenger RNA. During splicing, introns are removed and exons are joined together.
This presentation is about the transcription machinery that is required for the transcription in eukaryotes. The comparison between the transcription factors involved in prokaryotes and eukaryotes. The initiation of transcription and how it helps in producing a mRNA.
RNA splicing, in molecular biology, is a form of RNA processing in which a newly made precursor messenger RNA transcript is transformed into a mature messenger RNA. During splicing, introns are removed and exons are joined together.
This presentation is about the transcription machinery that is required for the transcription in eukaryotes. The comparison between the transcription factors involved in prokaryotes and eukaryotes. The initiation of transcription and how it helps in producing a mRNA.
Structure and function of Messenger RNA (mRNA )ICHHA PURAK
This presentation of 42 slides delivers information about structure,function synthesis , life span of both prokaryotic and eukaryotic messenger RNA also about role in protein sorting and targetting
Eukaryotic transcription is carried out in the nucleus of the cell and proceeds in three sequential stages: initiation, elongation, and termination. Eukaryotes require transcription factors to first bind to the promoter region and then help recruit the appropriate polymerase.
REGULATION OF
GENE EXPRESSION
IN PROKARYOTES & EUKARYOTES .
This presentation is enriched with lots of information of gene expression with many pictures so that anyone can understand gene expression easily.
Gene expression is the process by which the information encoded in a gene is used to direct the assembly of a protein molecule.
Gene expression is explored through a study of protein structure and function, transcription and translation, differentiation and stem cells.
It is the process by which information from a gene is used in the synthesis of a functional gene product.
These products are often proteins, but in non-protein coding genes such as ribosomal RNA (rRNA), transfer RNA (tRNA) or small nuclear RNA (snRNA) genes, the product is a functional RNA.
The process of gene expression is used by all known life - eukaryotes (including multicellular organisms), prokaryotes (bacteria and archaea)
Regulation of gene expression:
Regulation of gene expression includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA).
Gene regulation is essential for viruses, prokaryotes and eukaryotes as it increases the versatility and adaptability of an organism by allowing the cell to express protein when needed.
CLASSIFICATION OF GENE WITH RESPECT TO THEIR EXPRESSION:
Constitutive ( house keeping) genes:
Are expressed at a fixed rate, irrespective to the cell condition.
Their structure is simpler.
Controllable genes:
Are expressed only as needed. Their amount may increase or decrease with respect to their basal level in different condition.
Their structure is relatively complicated with some response elements.
TYPES OF REGULATION OF GENE:
positive & negative regulation.
Steps involving gene regulation of prokaryotes & eukaryotes.
Operon-structure,classification of mechanisms- lac operon,tryptophan operon ,
and many things related to gene expression.
This is a video slide so anyone can understand this topic easily by seeing pictures included in this slide.
A mutation is a change that occurs in our DNA sequence, either due to mistakes when DNA is copied or as the result of environmental factors such as UV light. The DNA sequence of a gene can be altered in a number of ways. Gene mutations have varying effects on health, depending on where they occur and whether they alter the function of essential proteins. Mutations are two types that are Gene mutation and Chromosome mutation. Gene mutation are further divided into Point and frameshift mutation. Point mutation are three types ie. Silent mutation, Missense mutation and Nonsense mutation. Frameshift mutation are of two types that are addition and deletion. Chromosome mutations are further classified into Deletion, duplication, inversion and translocation.
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.
Structure and function of Messenger RNA (mRNA )ICHHA PURAK
This presentation of 42 slides delivers information about structure,function synthesis , life span of both prokaryotic and eukaryotic messenger RNA also about role in protein sorting and targetting
Eukaryotic transcription is carried out in the nucleus of the cell and proceeds in three sequential stages: initiation, elongation, and termination. Eukaryotes require transcription factors to first bind to the promoter region and then help recruit the appropriate polymerase.
REGULATION OF
GENE EXPRESSION
IN PROKARYOTES & EUKARYOTES .
This presentation is enriched with lots of information of gene expression with many pictures so that anyone can understand gene expression easily.
Gene expression is the process by which the information encoded in a gene is used to direct the assembly of a protein molecule.
Gene expression is explored through a study of protein structure and function, transcription and translation, differentiation and stem cells.
It is the process by which information from a gene is used in the synthesis of a functional gene product.
These products are often proteins, but in non-protein coding genes such as ribosomal RNA (rRNA), transfer RNA (tRNA) or small nuclear RNA (snRNA) genes, the product is a functional RNA.
The process of gene expression is used by all known life - eukaryotes (including multicellular organisms), prokaryotes (bacteria and archaea)
Regulation of gene expression:
Regulation of gene expression includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA).
Gene regulation is essential for viruses, prokaryotes and eukaryotes as it increases the versatility and adaptability of an organism by allowing the cell to express protein when needed.
CLASSIFICATION OF GENE WITH RESPECT TO THEIR EXPRESSION:
Constitutive ( house keeping) genes:
Are expressed at a fixed rate, irrespective to the cell condition.
Their structure is simpler.
Controllable genes:
Are expressed only as needed. Their amount may increase or decrease with respect to their basal level in different condition.
Their structure is relatively complicated with some response elements.
TYPES OF REGULATION OF GENE:
positive & negative regulation.
Steps involving gene regulation of prokaryotes & eukaryotes.
Operon-structure,classification of mechanisms- lac operon,tryptophan operon ,
and many things related to gene expression.
This is a video slide so anyone can understand this topic easily by seeing pictures included in this slide.
A mutation is a change that occurs in our DNA sequence, either due to mistakes when DNA is copied or as the result of environmental factors such as UV light. The DNA sequence of a gene can be altered in a number of ways. Gene mutations have varying effects on health, depending on where they occur and whether they alter the function of essential proteins. Mutations are two types that are Gene mutation and Chromosome mutation. Gene mutation are further divided into Point and frameshift mutation. Point mutation are three types ie. Silent mutation, Missense mutation and Nonsense mutation. Frameshift mutation are of two types that are addition and deletion. Chromosome mutations are further classified into Deletion, duplication, inversion and translocation.
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.
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
The flow of information in the cell starts at DNA, which replicates to form more DNA. Information is then ‘transcribed” into RNA, and then it is “translated” into protein.
Information does not flow in the other direction.
A few exceptions to the Central Dogma exist
some RNA viruses, called “retroviruses”.
Lecture 3 Facial cosmetic surgery
Maxillofacial Surgery
Dental Students Fifth Year second semester
Al Azhar University Gaza Palestine
Dr. Lama El Banna
https://twitter.com/lama_k_banna
Lecture 1 Facial cosmetic surgery
Maxillofacial Surgery
Dental Students Fifth Year second semester
Al Azhar University Gaza Palestine
Dr. Lama El Banna
https://twitter.com/lama_k_banna
Facial neuropathology Maxillofacial SurgeryLama K Banna
Lecture 4 facial neuropathology
Maxillofacial Surgery
Dental Students Fifth Year second semester
Al Azhar University Gaza Palestine
Dr. Lama El Banna
https://twitter.com/lama_k_banna
Lecture 2 Facial cosmetic surgery
Maxillofacial Surgery
Dental Students Fifth Year second semester
Al Azhar University Gaza Palestine
Dr. Lama El Banna
https://twitter.com/lama_k_banna
Lecture 12 general considerations in treatment of tmdLama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name 12 general considerations in the treatment of TMJ
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name TMJ temporomandibular joint
Lecture 10
Al Azhar University Gaza Palestine
Dr. Lama El Banna
https://twitter.com/lama_k_banna
Lecture 11 temporomandibular joint Part 3Lama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name TMJ temporomandibular joint Part 3
Lecture 11
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name TMJ anatomy examination 2
Lecture 9
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Lecture 7 correction of dentofacial deformities Part 2Lama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name Correction of dentofacial deformities Part 2
Lecture 7
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Lecture 8 management of patients with orofacial cleftsLama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name management of patients with orofacial clefts
Lecture 8
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Lecture 5 Diagnosis and management of salivary gland disorders Part 2Lama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name Salivary gland 2
Diagnosis and management of salivary gland disorders Part 2
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Lecture 6 correction of dentofacial deformitiesLama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name Correction of dentofacial deformities
Lecture 6
Al Azhar University Gaza Palestine
Dr. Lama El Banna
lecture 4 Diagnosis and management of salivary gland disordersLama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name Salivary gland
Diagnosis and management of salivary gland disorders
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Maxillofacial Surgery 1
Dental Students Fifth Year First semester
Lecture Name maxillofacial trauma Part 3
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name maxillofacial trauma part 2
Al Azhar University Gaza Palestine
Dr. Lama El Banna
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
Title: Sense of Taste
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 structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
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.
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
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdfAnujkumaranit
Artificial intelligence (AI) refers to the simulation of human intelligence processes by machines, especially computer systems. It encompasses tasks such as learning, reasoning, problem-solving, perception, and language understanding. AI technologies are revolutionizing various fields, from healthcare to finance, by enabling machines to perform tasks that typically require human intelligence.
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
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
Surat @ℂall @Girls ꧁❤8527049040❤꧂@ℂall @Girls Service Vip Top Model Safe
The flow of genetic information transcription
1. The Flow of GeneticThe Flow of Genetic
Information: Transcription andInformation: Transcription and
TranslationTranslation
2. Central Dogma of Molecular Biology:
The Flow of Genetic Information
3. • The flow of genetic information is unidirectional and requires two major
steps: transcription and translation.
• First, the information of the gene is transcribed into an intermediary RNA
molecule, which is synthesized in sequences that are precisely
complementary to those of the strand of DNA (transcription).
• During the second major step the sequence information in the messenger
RNA molecule (mRNA) is translated into a corresponding sequence of
amino acids (translation).
• The length and sequence of the amino acid chain specified by a gene
results in a polypeptide with a biological function (gene product) or The
proteins which do most of the work in the cell.
• The main concept in the central dogma is that DNA does not code for
protein directly but acts through an mediator molecule called ribonucleic
acid (RNA).
• Exceptions To The Central Dogma Exist: Reverse TranscriptionExceptions To The Central Dogma Exist: Reverse Transcription
• Some RNA viruses, called “retroviruses” make a DNA copy of themselves
using the enzyme reverse transcriptase.
• The DNA copy incorporates into one of the chromosomes and becomes a
permanent feature of the genome.
• The DNA copy inserted into the genome is called a “provirus”. This
represents a flow of information from RNA to DNA..
4. Transcription and translation in eukaryotic cells are separated in space andTranscription and translation in eukaryotic cells are separated in space and
time.time.
Extensive processing of primary RNA transcripts in eukaryotic cells.Extensive processing of primary RNA transcripts in eukaryotic cells.
5. Transcription
• Transcription is the synthesis of RNA molecules, with DNA as a template, and it is
the first step in the transfer of genetic information from genotype to phenotype. The
process is complex, and requires a number of protein components.
• The enzyme used in transcription is “RNA polymerase”.
• There are several forms of RNA polymerase.
• In eukaryotes, most genes are transcribed by RNA polymerase II.
• The raw materials for the new RNA are the 4 ribonucleoside triphosphates:
– ATP, CTP, GTP, and UTP.
• As with DNA replication, transcription proceeds 5’→ 3’: new bases are added to
the free 3’ OH group.
• Unlike replication, transcription does not need to build on a primer.
• Instead, transcription starts at a region of DNA called a “promoter”.
• For protein-coding genes, the promoter is located a few bases 5’ to (upstream from)
the first base that is transcribed into RNA.
• Promoter sequences are very similar to each other, but not identical. If many
promoters are compared, a “harmony sequence” can be derived. All promoters would
be similar to this harmony sequence, but not necessarily identical.
6. Classes of RNAClasses of RNA
• Ribosomal RNA (rRNA), along with ribosomal protein subunits, makes up the
ribosome, the site of protein assembly.
• Messenger RNA (mRNA) carries the coding instructions (specific sequence
=codons) for synthesizing polypeptide chains from DNA to the ribosome. Large
precursor molecules, which are termed pre-messenger RNAs (pre-mRNAs), are the
immediate products of transcription in eukaryotic cells. Pre-mRNAs are modified
extensively before they exit the nucleus for translation into protein. Prokaryotes do
not possess premRNA; in these cells, transcription takes place concurrently with
translation.
• Transfer RNA (tRNA) serves as the link between the coding sequence of
nucleotides in the mRNA and the amino acid sequence of a polypeptide chain.
• Each tRNA attaches to one particular type of amino acid and helps to incorporate
that amino acid into a polypeptide chain.
• Additional classes of RNA molecules are found in the nuclei of eukaryotic cells.
• Small nuclear RNAs (snRNAs) combine with small nuclear protein subunits to form
small nuclear ribonucleoproteins (snRNPs, affectionately known as “snurps”). The
snRNPs are analogous to ribosomes in structure, only smaller, and they typically
contain a single RNA molecule combined with approximately 10 small nuclear
protein subunits. Some snRNAs participate in the processing of RNA (spicing=
removal of introns)
• Small nucleolar RNAs (snoRNAs) take part in the processing of rRNA.
• Small cytoplasmic RNAs (scRNAs) Small RNA molecules that found in the
cytoplasm of eukaryotic cells are associated with rough endoplasmic reticulum and
involved in some protein functions.
7.
8. Process of TranscriptionProcess of Transcription
• Transcription starts with RNA polymerase binding to the promoter.
• Various other proteins (transcription factors) help RNA polymerase bind to the
promoter. Other DNA sequences further upstream from the promoter are also
involved.
• Once it is bound to the promoter, RNA polymerase unwinds a small section of the
DNA and uses it as a template to synthesize a complementary RNA copy of the
DNA strand.
• The DNA strand used that transcribed is called the template.
• the other strand (non-transcribed) is the “coding strand???!!!!”.
• Notice that the RNA is made from 5’ →3’ end, so the template strand is actually
read from 3’ → 5’.
• The mRNA transcribed from the template DNA is called the RNA sense strand.
• RNA transcribed under experimental conditions from the opposing DNA strand is
called antisense RNA.
• RNA polymerase proceeds down the DNA, synthesizing the RNA copy.
• In prokaryotes, each RNA ends at a specific terminator sequence.
• In eukaryotes transcription doesn’t have a definite end point; the RNA is given a
definitive termination point during RNA processing.
9.
10. •The nucleotide in the template strand at which transcription begins is designated
with the number +1.
• Transcription proceeds in the downstream direction, and nucleotides in the
transcribed DNA are given successive positive numbers.
•Downstream sequences are drawn, by convention, to the right of the transcription
start site (+1).
•Nucleotides that lie to the left of this site (+1) are called the upstream sequences
and are identified by negative numbers.
Gene Notation
11. A transcription unit includes: a promoter, an RNA-coding region, and a
terminator.
12. RNA is transcribed from one DNA strand (the template).
In most organisms, each gene is transcribed from a single DNA strand, but different
genes may be transcribed from one or the other of the two DNA strands.
13. Polycistronic transcription in Prokaryotes
COORDINATED GENE
EXPRESSION: clustered
genes (operon) controlled
by one promoter and
transcribed as polycistronic
mRNA and encode multiple
gene products
14.
15. Monocistronic transcription in Eukaryotes
Interrupted genes
(exons/introns)
Monocistronic mRNAs
Post-transcriptional
modifications (nuclear
encoded genes):
5’ CAP
3’ polyA tail
16.
17.
18.
19.
20.
21. Requirements ofRequirements of Transcription
1.DNA Template strand (reading in 3’ → 5’ direction)
2.Enzyme: RNA Polymerase adding ribonucleoside triphosphates
(rNTPs) : ATP, GTP, CTP, UTP in the 5’ →3’ direction
3.No primer is required
22. Prokaryotic RNA polymerase
• Prokaryotes typically possess only one type of RNA polymerase, which
catalyzes the synthesis of all classes of bacterial RNA: mRNA, tRNA, and
rRNA.
• Bacterial RNA polymerase is a large, multimeric enzyme (meaning that it
consists of several polypeptide chains).
• The prokaryotic RNA polymerase enzyme is made up of 5 subunits
(polypeptide chains).
• The subunits are named α (there are two of these), β, β’, and σ. Each of
the subunits has its own job to do in transcription.
• The role of the sigma (σ) factor or subunit is to recognize a specific DNA
sequence called the promoter, which lies just upstream of the gene to be
transcribed. Without sigma, RNA polymerase will initiate transcription at
a random point along the DNA.
• E. coli promoters contain two important regions. One centered around
nucleotide −10 usually has the sequence TATATT. This sequence is called
the −10 box (or the TATA box).
• The second, centered near nucleotide −35 often has the sequence
TTGACA. This is the −35 box.
23.
24.
25. Prokaryotic RNA polymerase
• On binding to the promoter sequence, the σ factor brings the other subunits (two of α
and one each of β and β’) of RNA polymerase into contact with the DNA to be
transcribed. This forms the closed promoter complex.
• The two α subunits are important as they help RNA polymerase to assemble on the
promoter
• The β subunit of RNA polymerase binds rNTP and joins them together by catalyzing
the formation of phosphodiester links as it moves along the DNA template.
• The β’ subunit helps to keep the RNA polymerase attached to DNA.
• For transcription to begin, the two strands of DNA must separate, enabling one
strand to act as the template for the synthesis of an RNA molecule. This formation is
called the open promoter complex.
• There are only two hydrogen bonds between A and T ; thus it is relatively easy to
separate the two strands at this point of the promoter region.
• DNA unwinds and rewinds as RNA polymerase advances along the double helix,
synthesizing an RNA chain as it goes.
• This produces a transcription bubble. The RNA chain grows in the 5’ →3’ direction,
and the template strand is read in the 3’ →5’ direction.
• When the RNA chain is about 10 bases long, the σ factor is released from RNA
polymerase and plays no further role in transcription.
26.
27. • RNA polymerase has to know when it has reached the end of a gene.
• Escherichia coli has specific sequences, called terminators, at the ends of
its genes that cause RNA polymerase to stop transcribing DNA.
• A terminator sequence consists of two GC rich regions that are
separated by about 10 bp. This sequence is followed by a stretch of A
bases.
• When the GC-rich regions are transcribed, a hairpin loop forms in the
RNA with the first and second GC-rich regions aligning and pairing
up.
• Formation of this hairpin loop within the RNA molecule causes the
transcription bubble to shrink because where the template DNA strand
can no longer bind to the RNA molecule it reconnects to its sister DNA
strand.
• The RNA molecule is then released, transcription terminates, and the
double helix reforms.
• This type of transcription termination is known as rho-independent
termination.
• Some E. coli genes contain different terminator sites. These are recognized
by a protein, known as rho, which frees the RNA from the DNA. In this
case transcription is terminated by a process known as rho-dependent
termination.
Termination of prokaryotic transcription
28.
29. Transcription in Eukaryotes
• Eukaryotes have three types of RNA polymerase.
• In eukaryotic cells, DNA is complexed with histone proteins in highly compressed
chromatin.
• Before transcription, the chromatin structure is modified so that the DNA is in a
more open configuration and is more accessible to the transcription machinery.
• Several types of proteins have roles in chromatin modification.
• Acetyltransferases add acetyl groups to amino acids at the ends of the histone
proteins, which destabilizes the nucleosome structure and makes the DNA more
accessible.
• In addition, proteins called chromatin- remodeling proteins may bind to the
chromatin and displace nucleosomes from promoters and other regions important
for transcription.
30. Transcription in eukaryotesTranscription in eukaryotes
• The interaction of RNA polymerase with its promoter is far more complex in eukaryotes than it
is in bacteria.
• RNA polymerase II cannot recognize a promoter sequence. Instead, other proteins known as
transcription factors bind to the promoter and guide RNA polymerase II to the beginning of the
gene to be transcribed.
• A promoter for a gene transcribed by RNA polymerase II typically consists of two primary
parts: the core promoter and the regulatory promoter.
• The core promoter is located immediately upstream of the genecore promoter is located immediately upstream of the gene and typically contains AT-rich
sequence about 25 -30 bp upstream of the transcription start site. This sequence, called the
TATA box, binds a protein called the transcription factor IID (TFIID), one of whose subunits is
called the TATA-binding protein, or TBP.
• Mutations in the sequence of the TATA box affect the rate of transcription, and changing its
position alters the location of the transcription start site.
• Several other transcription factors (TFIIA, TFIIB, TFIIE, TFIIF, and TFIIH) then bind to
TFIID and to the promoter region.
• TFIIF is the protein that guides RNA polymerase II to the beginning of the gene to be
transcribed.
• The complex formed between the TATA box, TFIID, the other transcription factors, and RNA
polymerase is known as the transcription pre-initiation complex.
• The regulatory promoter is located immediately upstream of the core promoter. Some
transcriptional activator proteins bind to regulatory promoter and, either directly or indirectly
affects the rate at which transcription is initiated.
• Some regulatory promoters also contain repressing (suppressing) sequences, which are bound
by proteins that lower the rate of transcription through inhibitory inactions with the mediator.
31.
32. Transcription in Eukaryotes
• Enhancers are DNA sequences that increase the rate of transcription at
distant genes. The precise position of an enhancer relative to a gene’s
transcriptional start site is not critical; most enhancers can stimulate any
promoter in their neighborhood. An enhancer may be upstream or
downstream from the affected gene or, in some cases, within an intron of
the gene itself. Enhancers also contain sequences that are recognized by
transcriptional activator proteins.
• Transcription in Eukaryotes begins when the carboxy-terminal domain
of RNA polymerase II is phosphorylated. This region is rich in the amino
acids serine and threonine each of which contains an OH group in their
side chain. When these OH groups are phosphorylated, RNA polymerase II
breaks away from the pre-initiation complex and proceeds to transcribe
DNA into mRNA.
33.
34. Transcription apparatus. The TATA-binding protein (TBP), a component of TFIID, binds toTranscription apparatus. The TATA-binding protein (TBP), a component of TFIID, binds to
the TATA box. Transcription factors TFII A and B bind to TBP. RNA polymerase binds,the TATA box. Transcription factors TFII A and B bind to TBP. RNA polymerase binds,
then TFII E, F, and H bind. This complex can transcribe at a basal level. Some coactivatorthen TFII E, F, and H bind. This complex can transcribe at a basal level. Some coactivator
proteins are present as a component of TFIID, and these can bind to other regulatory DNAproteins are present as a component of TFIID, and these can bind to other regulatory DNA
binding proteins (called specific transcription factors ortranscriptional activators).binding proteins (called specific transcription factors ortranscriptional activators).
35.
36. A schematic view of a eukaryotic gene.. The gene consists of promoter and transcribedA schematic view of a eukaryotic gene.. The gene consists of promoter and transcribed
regions. The transcribed region contains introns, and exons. The first RNA formregions. The transcribed region contains introns, and exons. The first RNA form
produced is heterogenous nuclear RNA (hn RNA) or premature RNA or primaryproduced is heterogenous nuclear RNA (hn RNA) or premature RNA or primary
transcript, which contains both intronic and exonic sequences. The hnRNA is modifiedtranscript, which contains both intronic and exonic sequences. The hnRNA is modified
such that a cap is added at the 5 end (cap site), and a poly-A tail added to the 3 end.such that a cap is added at the 5 end (cap site), and a poly-A tail added to the 3 end.
The introns are removed (a process called splicing) to produce the mature mRNA orThe introns are removed (a process called splicing) to produce the mature mRNA or
final transcript , which leaves the nucleus to direct protein synthesis in the cytoplasm.final transcript , which leaves the nucleus to direct protein synthesis in the cytoplasm.
Py is pyrimidine (C or T).Py is pyrimidine (C or T).
37. Messenger RNA Processing: 5’ capping.
• A newly synthesized
eukaryotic mRNA (pre
mRNA) undergoes several
modifications before it leaves
the nucleus.
• The first is known as 5’
capping. Very early in
transcription the 5-terminal
triphosphate group is modified
by the addition of a guanosine
via a 5’-5’-phosphodiester
link (triphosphate linkage) .
The guanosine is subsequently
methylated to form the 7-
methyl guanosine cap.
38.
39. Messenger RNA Processing: poly-A tail
• The 3’ ends of nearly all eukaryotic mRNAs are modified by the addition of a long
stretch of adenosine residues, the poly-A tail .
• A sequence AAUAAA is found in most eukaryotic mRNAs about 20 bases from
where the poly-A tail is to be added and is probably a signal for the enzyme poly-A
polymerase to bind and to begin the polyadenylation process.
• The length of the poly-A tail varies, it can be as long as 250 nucleotides. Unlike
DNA, RNA is an unstable molecule, and the capping of eukaryotic mRNAs at their
5 ends and the addition of a poly-A tail to their 3 end increases the lifetime of
mRNA molecules by protecting them from digestion by nucleases.
40. Messenger RNA Processing: Exons /Introns splicing
• Eukaryotic protein-coding genes are split into exon and intron sequences. Both the
exons and introns are transcribed into mRNA.
• The introns have to be removed and the exons joined together by a process known as
RNA splicing before the mRNA can be used to make protein.
• RNA splicing takes place within the nucleus.
• Within an mRNA the first two bases following an exon are always GU and the last
two bases of the intron are AG.
• Several small nuclear RNAs (snRNAs) are involved in splicing. These are
complexed with a number of proteins to form a structure known as the spliceosome.
• One of the snRNAs is complementary in sequence to either end of the intron
sequence. It is thought that binding of this snRNA to the intron, by complementary
base pairing, brings the two exon sequences together, which causes the intron to loop
out .
• The proteins in the spliceosome remove the intron and join the exons together.
Splicing is the final modification made to the pre mRNA in the nucleus. The mRNA
is now transported to the cytoplasm for protein synthesis.
• Exception: As well as removing introns, splicing can sometimes remove exons in a
process called alternative splicing. This allows the same gene to give rise to
different proteins at different times or in different cells.
• For example, alternative splicing of the gene for the molecular motor dynein
produces motors that transport different types of cargo