Microbial genetics is a subject area within microbiology and genetic engineering. This involves the study of the genotype of microbial species and also the expression system in the form of phenotypes
BRIEFLY EXPLAINED PPT ABOUT RESTRICTION ENZYMES, THEIR WORKING SITES, TYPES, ARTIFICIALLY GENERATED RESTRICTION ENZYMES, THEIR MECHANISM OF ACTION, TYPES OF CUTS THEY MAKE, THEIR NOMENCLATURE ETC.
Microbial genetics is a subject area within microbiology and genetic engineering. This involves the study of the genotype of microbial species and also the expression system in the form of phenotypes
BRIEFLY EXPLAINED PPT ABOUT RESTRICTION ENZYMES, THEIR WORKING SITES, TYPES, ARTIFICIALLY GENERATED RESTRICTION ENZYMES, THEIR MECHANISM OF ACTION, TYPES OF CUTS THEY MAKE, THEIR NOMENCLATURE ETC.
Recombinant baculoviruses are widely used to
express heterologous genes in cultured insect cells
and insect larvae. For large-scale applications, the
baculovirus expression vector system (BEVS) is particularly
advantageous.
Recombinant baculoviruses are widely used to
express heterologous genes in cultured insect cells
and insect larvae. For large-scale applications, the
baculovirus expression vector system (BEVS) is particularly
advantageous.
• Define transcription• Define translation• What are the 3 steps.pdfarihantelehyb
• Define transcription
• Define translation
• What are the 3 steps of translation?
• Define the “genetic dogma”
• What is the function of Transfer RNA?
• What is the function of RNA polymerase?
• What is the function of DNA polymerase?
• Define “splicing of RNA”
• What is an exon?
• What component of the cell does the translation?
• What molecule in the cell does transcription?
• What are the functions of: operon, promotor?
• What is the difference between inducible operon and repressible operon?
Solution
• Define transcription
Transcription is the process of making an RNA copy of a gene sequence. This copy, called a
messenger RNA (mRNA) molecule, leaves the cell nucleus and enters the cytoplasm, where it
directs the synthesis of the protein, which it encodes. Here is a more complete definition of
transcription.
• Define translation
Translation is the process of translating the sequence of a messenger RNA (mRNA) molecule to
a sequence of amino acids during protein synthesis. The genetic code describes the relationship
between the sequence of base pairs in a gene and the corresponding amino acid sequence that it
encodes. In the cell cytoplasm, the ribosome reads the sequence of the mRNA in groups of three
bases to assemble the protein. Here is a more complete definition of translation:
• What are the 3 steps of translation?
Step # 1. Initiation:
Initiation of translation in E .coli involves the small ribosome subunit, a mRNA molecule, a
specific charge initiator tRNA, GTP, Mg++ and number of proteinaceous initiation factors (IFs).
These are initially part of the small subunit and are required to enhance binding affinity of the
various translational components (Table 8.1). Unlike ribosomal proteins, IFs are released from
the ribosome once initiation is completed.
Step # 2. Elongation:
Once both subunits of the ribosome are assembled with the mRNA, binding site for two charged
tRNA molecules are formed. These are designated as the ‘P’ or peptidyl and the ‘A’ or
aminoacyl sites. The charged initiator tRNA binds to the P site, provided that the AUG triplet of
mRNA is in the corresponding position of the small subunit. The increase of the growing
polypeptide chain by one amino acid is called elongation.
Step # 3. Termination:
Termination of protein synthesis is carried out by triplet codes (UAG, UAA, UGA; stop codons)
present at site A. These codons do not specify an amino acid, nor do they call for a tRNA in the
A site. These codons are called stop codons, termination codons or nonsense codons. The
finished polypeptide is still attached to the terminal tRNA at the P site, and the A site is empty.
• Define the “genetic dogma”
A theory in genetics and molecular biology subject to several exceptions that genetic information
is coded in self-replicating DNA and undergoes unidirectional transfer to messenger RNAs in
transcription which act as templates for protein synthesis in translation
• What is the function of Transfer RNA?
The tRNA molecule, or tr.
As a periodontist, it is of utmost importance to understand the genetic basis of inheritance in periodontal diseases be able to relate to the various polymorphisms associated with periodontal diseases. This ppt presents the basics of genetics from the point of view of future understanding of polymorphisms related to periodontal diseases.
NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
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.
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
New Drug Discovery and Development .....NEHA GUPTA
The "New Drug Discovery and Development" process involves the identification, design, testing, and manufacturing of novel pharmaceutical compounds with the aim of introducing new and improved treatments for various medical conditions. This comprehensive endeavor encompasses various stages, including target identification, preclinical studies, clinical trials, regulatory approval, and post-market surveillance. It involves multidisciplinary collaboration among scientists, researchers, clinicians, regulatory experts, and pharmaceutical companies to bring innovative therapies to market and address unmet medical needs.
Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
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Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
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
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.
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
2. • DEFINITION
• CENTRAL DOGMA
• EXTRACHROMOSOMAL GENETIC ELEMENTS
• MUTATION
• TRANSMISSION OF GENETIC MATERIAL
26-06-2021 2
3. GENETICS……
defines & analyses heredity i.e., constancy and variation
in the physiologic functions, that form the properties of an organism.
The term was coined by British biologist William Bateson in 1906.
26-06-2021 3
4. UNDERSTANDING GENETICS
We resemble and differ because of Genetic configurations
Parents - Son - Daughter, how they resemble each other.
They breed true from Generation to Generation
But vary in small proportions in progeny.
Bacteria too obey the laws of Genetics
5. Gregor Mendel ….. Formulated the basic rules of heredity in 1865.
Thomas Morgan (1866-1945)… the founder of modern genetics, showed
chromosomes contain genes & won Nobel prize, 1933.
7. Beginning of Bacterial Genetics
Since 1940s principles of genetics were applied to bacteria &
viruses.
Better understanding of genetic process has led to the birth of a
new branch of science, MOLECULAR BIOLOGY..
9. Genetic Materials
DNA & RNA
DNA -deoxyribonucleic acid
RNA -ribonucleic acid
Nucleotides
◦ Phosphate group
◦ Pentose sugar
◦ Nitrogenous base
10. Structure of DNA
Double stranded (double helix)
Chains of nucleotides
5’ to 3’ (strands are anti-parallel)
Complimentary base pairing
◦ A-T
◦ G-C
12. DNA Structure
◦ The double stranded structure stabilized by hydrogen bonding b/n nitrogenous bases
of opposite strands.
◦ Purine bases are Adenine, Guanine
◦ Pyrimidine bases are Thymine, Cytosine.
◦ A+T/G+C ratio remains constant for each bacterial species.
26-06-2021 12
13. Bacterial Chromosome
Bacterial chromosome consists of a double stranded molecule of
DNA arranged in a circular form
1000µm in length
1kb=1000 base pairs
Bacterial DNA about 4000kb
Human genome about 3 million kb long
14. DNA Replication
Semiconservative type of DNA replication
In daughter cell, one strand is derived from the mother cell &
other strand is newly synthesized
15. DNA Replication-occurs at the replication
fork
5’ to 3 ‘
DNA helicase-unzips + parental DNA strand that is used as a template
◦ Leading strand (5’ to 3’-continuous)
*DNA polymerase-joins growing DNA strand after nucleotides are aligned
(complimentary)
◦ Lagging strand (5’ to 3’-not continuous)
*RNA polymerase (makes short RNA primer)
*DNA polymerase (extends RNA primer then digests RNA primer and replaces it with DNA)
*DNA ligase (seals Okazaki fragments-the newly formed DNA fragments)
18. Replication of bacterial circular DS-DNA begins at the ori
locus
Chromosome replication termination regions are called
ter.
They are located at opposite points on the circular DNA
chromosome
21. 3 Types of RNA
1. mRNA (messenger RNA)
◦ Contains the codons
2. r RNA (ribosomal RNA)
◦ Ribosomes (70S)
3. t RNA (transfer RNA)
◦ Transfer amino acids to the ribosomes for protein synthesis
◦ Anti-codon
22. Template strand DNA strand which is transcribed to give rise to
m-RNA
Coding strand the opposite DNA strand which has the same
sequence of that of m-RNA
26-06-2021 22
23. Basic principles of molecular biology
Central dogma of molecular biology
DNA
Transcription
RNA
Translation
POLYPEPTIDE
26-06-2021 23
24. The template strand of DNA is transcribed into a SS m-RNA by DNA
depended RNA polymerase
Steps
Initiation
Elongation
Termination
Post transcriptional modification
26. INITIATION
Promoter region : certain specific areas on the DNA to which RNAP
attaches.
Transcription unit : The region b/n promoter & terminator sites.
TATA Box : it act as the signal for the start region
Enhancers : increase the rate of transcription.
27. ELONGATION
The RNAP moves along the DNA template & new nucleotides are
incorporated in the nascent m-RNA.
Transcription bubble is formed by
RNAP, DNA & nascent RNA
29. TERMINATION
Rho independent….it is an
interrupted invert repeat
DNA sequence &
is transcribed
The m-RNA produced will
form intrachain base pairing
to make a hairpin structure
this obstruct further movement of
RNAP
30. POST TRANSCRIPTIONAL MODIFICATION
In eukaryotes, the primary transcript undergoes extensive editing to become
mature m-RNA.
Poly A tailing, 5`capping, removal of introns & connection of exons.
In bacteria m-RNA is not changed & translation starts even before completion
of transcription.
31.
32. TRANSFER RNA
Transfer amino acids from cytoplasm to
the ribosomal protein synthesizing
machinery
Structure
Acceptor arm at 3` end…carries amino acid
Anticodon arm…recognizes the triplet
nucleotide codon in m-RNA
DHU arm…recognition site for enzyme
which adds the amino acid
Pseudo uridine arm…binds t-RNA to
ribosomes
33. RIBOSOMAL RNA
They are structural components of ribosomes
Ribosomal assembly is the protein synthesizing machinery
Bacteria has 70S ribosomes with 30S & 50S subunits
Bacterial ribosomes contain 3 types of r-RNA
34. What is a Gene
Gene is a sequence of DNA
carrying codons specifying for
particular polypeptide
DNA contains many Genes( A
combinations of hundreds and
thousands of Nucleotides )
35.
36. GENETIC CODE
Genetic information in DNA is stored as a triplet code, which consists of 3
bases.
Each triplet code is transcribed to m-RNA & it has codons which specifies for a
single amino acid
Codon is degenerate…more than one codon may exist for same amino acid
Genetic Code is Universal…the codons are the same for the same amino acid in
all species
37. CODON
Codons code for a specific amino acid
3 base code - 4 bases ( A,U,G,C )
64 possible combinations ( 43)
20 amino acids
Nonsense / terminator codons…do not code for any amino acid
E.g. : UAA, UAG, UGA
Initiator codon…AUG act as the initiator codon
38.
39. How bacterial Genome differs from Higher
forms of Life
Several stretches of DNA don't appear to function as codons, occurs between
the coding sequences of gene called as INTRONS
Coded are called as EXONS
In transcription introns are excised when form RNA before translated by
ribosomal proteins.
41. REGULATION OF GENE EXPRESSION
Synthesis of proteins under the influence of gene is called gene expression
All genes are not always being expressed
Genes turned on all the time - Constitutive
Enzymes are synthesized irrespective of
the conc. of the substrate
Other genes can be regulated by either induction / turned on or repression / turned off
42. LAC OPERON
Lac - Lactose (disaccharide)
◦ Glucose and Galactose
Operon - series of structural genes, all under the control of a Regulatory Gene
lac operon is normally turned off
lac operon is an Inducible operon
45. TRYPTOPHAN OPERON
Tryptophan - amino acid
Operon - series of structural genes, all under the control of a regulatory gene
Tryptophan operon is normally turned on
Tryptophan operon is a repressible operon
46.
47.
48. • DEFINITION
• CENTRAL DOGMA
• EXTRACHROMOSOMAL GENETIC ELEMENTS
• MUTATION
• GENE TRANSFER
49. EXTRACHROMOSOMAL GENETIC ELEMENTS
Bacteria posses extra chromosomal genetic elements not essential
for survival of bacteria
But makes the bacteria resistant to antibiotics, and makes them
survive, able to produce toxins
50. PLASMIDS
They are circular DNA molecule in the cytoplasm of bacteria
Capable of autonomous replication (independent replicons)
Can transfer genes from one cell to other
act as vectors in genetic engineering
Can also be present in yeasts
51. PLASMIDS
Plasmid seem to be ubiquitous in bacteria, May encode genetic information for properties
Resistance to Antibiotics
Bacteriocin production
Enterotoxin production
Enhanced pathogenicity
Reduced sensitivity to mutagens
Degrade complex organic molecules
52. Can be integrated with Chromosomal DNA
Episomes -Integrated form of plasmid with DNA
53. CLASSIFICATION
Based on restriction endonuclease fingerprints from purified plasmid DNA
The pattern of fragments produced is dependent on the distribution of the
specific DNA sequences recognized by the enzyme
Closely related plasmids will produce same or very similar fingerprints
Unrelated plasmids will produce different fingerprints
54. By incompatibility testing
Based on the fact that, closely related plasmids are unable to coexist stably in the same
bacterial cell
Plasmids belonging to the same incompatibility group are closely related & interfere with one
another’s replication
Unrelated plasmids can coexist stably & belong to different incompatibility group
55. By using specific virulent bacteriophages
They will adhere only to the type of pilus produced by a particular group of
plasmids
Lysis by such a phage allows the identification of the group to which the
plasmid contained in the cell belongs
56. GENOTYPE PHENOTYPE
The sum total of the genes that make up the
genetic apparatus of a cell.
The physical expression of the genotype in a given
environment
Genotypic variations are stable, heritable & not
influenced by the environment.
They are temporary, not heritable & influenced by
the environment.
E.g.: mutation, transformation, transduction,
conjugation
E.g.: loss of flagella of typhoid bacilli in phenol agar.
57. • DEFINITION
• CENTRAL DOGMA
• EXTRACHROMOSOMAL GENETIC ELEMENTS
• MUTATION
• TRANSMISSION OF GENETIC MATERIAL
58. MUTATION
A random, undirected, heritable variation caused by an alteration in
the nucleotide sequence at some point of the DNA of the cell.
Macro lesions ( Multisite mutations) involve extensive
chromosomal rearrangements such as deletion, duplication,
inversion.
Micro lesions (Point mutations) affects one or very few nucleotides
59. POINT MUTATION
BASE PAIR SUBSTITUTION:
TRANSITION -- when a purine is replaced by another purine or a pyrimidine by another pyrimidine.
TRANSVERSION -- It is the substitution of a purine for a pyrimidine and vice versa in a base pairing
64. MUTATIONS
Suppressor mutation: reversal of mutant phenotype by another mutation at
a position distinct from that of original position
Lethal mutation : involve vital functions & such mutants are nonviable
E.g.: a conditional lethal mutant—able to live under certain permissive
conditions like temp sensitive mutant
65. MUTAGENIC AGENTS
U V rays
Alkylating agents
Acridine dyes
5-bromouracil
2-aminopurine
66. • DEFINITION
• CENTRAL DOGMA
• EXTRACHROMASOMAL GENETIC ELEMENTS
• MUTATION
• GENE TRANSFER
67. GENE TRANSFER
Mechanisms of gene transfer
1.VERTICAL INHERITANCE
inheritance of parental genes
2. LATERAL (HORIZONTAL) gene transfer
DNA can be transferred from one organism to another & cause permanent
stable change in recipient’s genetic composition.
E.g.: Transformation, Transduction & Conjugation
68. TRANSFORMATION
The transfer of genetic information through the agency of free DNA
Cells that are able to take up DNA from their environment & incorporate it into
the genome are said to be competent
Competence involves the ability to bind DNA to the cell surface & then
transport it through the cell envelope into the cytoplasm prior to incorporation
into the genome
70. Cont.….
Natural competence shown by
S . Pneumoniae , B .subtilis & H. influenzae
S . pneumoniae & B .subtilis take up heterospecific & homospecific bacterial DNA
H.influenzae & Neisseria gonorrhoea homospecific (closely related) DNA only.
In systems that rely on natural competence, transformation with homospecific
chromosomal DNA is much more efficient
71. Cont.….
Artificial competence commonly seen in E.coli , P.aeruginosa, S.aureus
Induced by treatment of bacteria with calcium chloride at 0 degree C
Cell suspensions are mixed with free DNA and are subject to electrical discharge
through the suspension, termed Electroporation
Application in recombinant DNA technology
72. TRANSFORMATION
Ist observation of bacterial transformation was by Griffith 1928
GRIFFITH’S EXPERIMENT
Mice injected with Live non capsulated ( R ) Pneumococci
with heat killed capsulated (S) Pneumococci lead to death of mice
with isolation of live capsulated Pneumococci
It means that some factor from Dead pneumococci transferred to live non pathogenic
Pneumococci
73. TRANSFORMATION
The nature of the transforming principle was identified as DNA by
Avery, Macleod & McCarty in 1944
75. TRANSDUCTION
The transfer of a portion of the DNA from one bacterium to another by a bacteriophage
2 forms
Generalized …..any part of the donor genome can be transferred to a suitable recipient
Specialized…..specific sequences are transferred
76.
77. RESTRICTED TRANSDUCTION
Lambda phage of E.coli
Prophage lambda inserts only b/n the genes determining
Galactose utilization (gal) & biotin synthesis (bio)
It transduces only either of these
78. BACTERIOPHAGE
A virus that parasitize bacteria
A nucleic acid core & a protein coat
2 types of lifecycle
Virulent / lytic & Temperate / non lytic cycles
79.
80.
81. LYSOGENIC CONVERSION
Prophage…phage DNA integrated with bacterial chromosome
Lysogenic bacteria…bacteria harboring prophages
Lysogeny…process of prophage multiplying synchronously with the host DNA &
transferring to daughter cells
Phage conversion…the prophage DNA confers new genetic information to a bacterium
82. Cont.…
Episomes & plasmids may also be transduced
The plasmids determining penicillin resistance in Staphylococci are transferred by
transduction
Most widespread mechanism of gene transfer among prokaryotes
Transduction provides an excellent tool for the genetic engineering
83. CONJUGATION
The transfer of DNA directly from one bacterial cell to another by a mechanism that requires
cell-to-cell contact
Discovered by Lederberg and Tatum (1946)
in a strain of E . coli K 12
Plasmids are the genetic elements most frequently transferred
84. Self transmissible plasmids contain the tra gene which encodes
the genetic functions for cell contact & transfer
DNA transferred during conjugation through the plasmid
include
1.Fertility (F) factor
2.Colicinogenic (Col) factor
3.Resistance transfer factor (RTF)
85. F factor
The maleness or donor status of a cell is indicated by a specialized fimbria (sex pili)
Sex pili act as conjugation tube
Retraction of pilus brings the cells into close contact & a pore forms in the adjoining cell
membrane
In plasmid DNA a single stranded nick occurs at oriT & the 5`end of a single strand is transferred
to the recipient
86.
87.
88.
89. The F factor is actually an episome & in some cells they exist in the integrated state
They are Hfr cells
Have ability to transfer chromosomal genes to recipient cells with high frequency
Following conjugation with an Hfr cell, an F- only rarely becomes F+
This conversion of an F+ cell into the Hfr state is reversible
92. SEXDUCTION
When the F factor reverts from the integrated state to the free state; it may sometimes carry
some chromosomal genes from near its site of attachment
Such F factor is called F prime factor
The process of transfer of host genes through the F prime factor resembles transduction & so
named as sexduction
93. Col factor
Colicin production is determined by a plasmid called Col factor, which
resembles the F factor
Colicins…..Antibiotic like substances which are specifically & selectively
lethal to enterobacteriae
Similar substances are produced by bacteria other than coliforms also & so
collectively termed as Bacteriocin
94. RESISTANCE TRANSFER FACTOR
This plasmid leads to the spread of multiple drug resistance among bacteria
The plasmid R factor consists of 2 components
The RTF…..for conjugational transfer
Resistance determinant (r) ….for each of
the several drugs
95. RTF & the ‘r’ determinants may exist as separate plasmids
Then the drug resistance is not transferable
The host cell remains drug resistant
Transferable drug resistance is seen in…..Enterobacteriaceae, Vibrio, Pseudomonas, Pasteurella
96. The transfer of drug resistance is inhibited by…
1. Anaerobic conditions
2. bile salts
3. alkaline pH
4. the abundance of anaerobic Gram positive bacteria by minimizing
the contact b/n donor cells & recipient cells
97. MOBILE GENETIC ELEMENTS
Structurally & genetically discrete segments of DNA
They move around in a cut & paste manner b/n chromosomal &
extra chromosomal DNA molecules within cells
98. They are also called Jumping genes
Depend on chromosomal or plasmid DNA for replication
No genetic homology is needed for transfer of DNA molecule
by Transposition
Discovered by Barbara McClintock
99. A segment of DNA with one or more genes in the centre & the two ends with
inverted repeat sequences of nucleotides
100. 2 types
Insertion sequence elements (IS)
small (1-2kb) & encode only those functions needed for their own transposition
Structure
Unique central sequence encoding the transposition function.
Flanked by short inverted repeat sequence
101. Transposons
larger (4-25kb) & encode atleast one function unconnected to transposition, that alters
the cell phenotype
E.g.: antibiotic resistance…..
TEM-2- beta lactamases
2 types
Composite transposon
Complex transposon
102. Composite transposon
Constructed from recognizable simpler units
Unique central sequence encodes the specific functions & lack transposition functions
The terminal sequence repeats comprise a pair of IS elements with transposition functions
e.g. Tn5,Tn7
103. Complex transposon
They do not have modular structures
Both transposition & non transposition functions are located in the bulk of the sequence
Flanked by short terminal inverted repeats
TnA or Tn1
104. Some transposons move by replicative manner
E.g. Tn1
Others non replicative (conservative) i.e. they move without making a copy of themselves
eg:Tn7
105. Integrons
A mobile DNA element
They can replicate & carry gene, particularly those responsible for antibiotic resistance by site
specific recombination
5` conserved region have a gene int encoding integrase, a site specific recombinase
attl site besides int is recognised & utilized by the integrase to capture gene cassettes
106. The antibiotic resistance genes that integron capture are located on gene cassettes
These gene cassettes exist as free circular DNA
A recombination event occurs, integrating the cassette into the integron
They are classified based on the integrase gene they contain
E.g.: most recently identified antibiotic resistance gene cassettes that encode the MBL