Mutations are changes in DNA that can occur for various reasons and have different effects. A single mutation can range from having no observable effect to causing serious genetic disorders. The document examines mutations at the molecular, cellular, organismal, and evolutionary levels through examples like sickle cell anemia. It describes the random nature of mutations and how an experiment by Esther and Joshua Lederberg provided evidence that antibiotic resistance arises from pre-existing mutations rather than being induced by antibiotic exposure.
To modifying the structure of a specific gene.
Gene targeting vector introduced into the cell.
Vector modifies the normal chromosomal gene through homologous recombination.
Useful in treating some human genetic disorders – Hemophilia, Duchenne Muscular Dystrophy.
Treating human diseases by genetic approaches – Gene Therapy.
Gene Therapy – Replacing the defective gene by normal copy of the gene.
Expressed sequence tag/EST is a short partial sequence, typically 200-400 bp long, of a complimentary DNA/Cdna.
EST is a short sub-sequence of a cDNA sequence.
Used to identify gene transcripts, and are instrumental in gene discovery and in gene-sequence determination.
Approximately 74.2 million ESTs are available in public databases.
EST results from one-short sequencing of a cloned cDNA.
Low-quality fragments.
Length is approximately 500 to 800 nucleotides.
To modifying the structure of a specific gene.
Gene targeting vector introduced into the cell.
Vector modifies the normal chromosomal gene through homologous recombination.
Useful in treating some human genetic disorders – Hemophilia, Duchenne Muscular Dystrophy.
Treating human diseases by genetic approaches – Gene Therapy.
Gene Therapy – Replacing the defective gene by normal copy of the gene.
Expressed sequence tag/EST is a short partial sequence, typically 200-400 bp long, of a complimentary DNA/Cdna.
EST is a short sub-sequence of a cDNA sequence.
Used to identify gene transcripts, and are instrumental in gene discovery and in gene-sequence determination.
Approximately 74.2 million ESTs are available in public databases.
EST results from one-short sequencing of a cloned cDNA.
Low-quality fragments.
Length is approximately 500 to 800 nucleotides.
N-terminal tails of histones are the most accessible regions for modifications. These post-translational modification (PTM) of histones is a crucial step in epigenetic regulation of a gene.
Epigenetics is the study, in the field of genetics, of cellular and physiological phenotypic trait variations that are caused by external or environmental factors that switch genes on and off and affect how cells read genes instead of being caused by changes in the DNA sequence. -Wikipedia
The process of transcription is the first stage of gene expression resulting in the production of a primary RNA transcript from the DNA of a particular gene.
This step of gene expression which is followed by a number of post-transcriptional processes such as RNA splicing and translation.
These lead ultimately to the production of a functional protein and this process is highly regulated.
Both basal transcription and its regulation are dependent upon specific protein factors known as transcription factors.
These highly specific protein bind to the specific regulatory gene of DNA sequence and control the transcription process and regulate it.
For example- enzyme RNA polymerase catalyzes the chemical reaction that synthesize RNA, using the DNA gene as a template, the transcription factor control when, where, and how efficiency RNA polymerase function.
Play an important role in the normal development and routine of cellular function.
N-terminal tails of histones are the most accessible regions for modifications. These post-translational modification (PTM) of histones is a crucial step in epigenetic regulation of a gene.
Epigenetics is the study, in the field of genetics, of cellular and physiological phenotypic trait variations that are caused by external or environmental factors that switch genes on and off and affect how cells read genes instead of being caused by changes in the DNA sequence. -Wikipedia
The process of transcription is the first stage of gene expression resulting in the production of a primary RNA transcript from the DNA of a particular gene.
This step of gene expression which is followed by a number of post-transcriptional processes such as RNA splicing and translation.
These lead ultimately to the production of a functional protein and this process is highly regulated.
Both basal transcription and its regulation are dependent upon specific protein factors known as transcription factors.
These highly specific protein bind to the specific regulatory gene of DNA sequence and control the transcription process and regulate it.
For example- enzyme RNA polymerase catalyzes the chemical reaction that synthesize RNA, using the DNA gene as a template, the transcription factor control when, where, and how efficiency RNA polymerase function.
Play an important role in the normal development and routine of cellular function.
Cell Biology and genetics paper - Mutation a basic touch to b.sc students with examples. DNA, genome, gene level mutation and chromosome level with examples. Touched some of the mutation types.
Describe how the structure of the DNA double helix was discovered. E.pdfarchanadesignfashion
Describe how the structure of the DNA double helix was discovered. Explain how DNA
ultimately controls the functioning of cells (be specific), and how/why mutations in DNA can
disrupt proper functioning. In chapter 2 you learned that the function of DNA and RNA is
\"information storage.\" Using what you\'ve teamed in Chapter 5, describe in detail the specific
functions of DNA and RNA. Explain the process of transcription. Explain the process of
translation. Briefly describe three types of mutations and explain how certain mutations can be
unrecognizable in an organism while others may have disastrous consequences. Summarize
three ways that genetic engineering is being used in agriculture. Explain three concerns
regarding the use of GMO\'s in agriculture How has genetic engineering technology been
directly applied to human health (most agriculture applications are indirect)? Has it been
successful? How are goals used to make medicine?
Solution
1 The function of DNA? depends to a large extent on its structure. The three-dimensional
structure of DNA was first proposed by James Watson and Francis Crick in 1953. It is one of the
most famous scientific discoveries of all time.
James and Francis used evidence shared by others, particularly Rosalind Franklin and Maurice
Wilkins, to determine the shape of DNA. Rosalind worked with Maurice at King\'s College
London. She beamed X-rays through crystals of the DNA molecule and then used photographic
film to record where the scattered X-rays fell. The shadows on the film were then used to work
out where the dense molecules lie in the DNA. This technique is called X-ray diffraction. The
DNA crystals resulted in a cross shape on the X-ray film which is typical of a molecule with a
helix shape. The resulting X-ray was named Photograph 51 and Maurice shared it with James
and Francis.
In 1953 James Watson and Francis Crick published their theory that DNA must be shaped like a
double helix. A double helix resembles a twisted ladder. Each \'upright\' pole of the ladder is
formed from a backbone of alternating sugar and phosphate groups. Each DNA base? (adenine,
cytosine, guanine, thymine) is attached to the backbone and these bases form the rungs. There
are ten \'rungs\' for each complete twist in the DNA helix.
James and Francis suggested that each \'rung\' of the DNA helix was composed of a pair of
bases, joined by hydrogen bonds?. According to Erwin Chargaff’s rules, A would always form
hydrogen bonds with T, and C with G.
2 - It is not the DNA itself that controls cellular functions, it is the proteins that are coded by the
DNA. The nucleotide sequences that make up DNA are a “code” for the cell to make hundreds of
different types of proteins; it is these proteins that function to control and regulate cell growth,
division, communication with other cells and most other cellular functions. This is why DNA is
said to “carry” or “store” information in the form of nucleotide sequences.
The sequences need to be “d.
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
Le nuove frontiere dell'AI nell'RPA con UiPath Autopilot™UiPathCommunity
In questo evento online gratuito, organizzato dalla Community Italiana di UiPath, potrai esplorare le nuove funzionalità di Autopilot, il tool che integra l'Intelligenza Artificiale nei processi di sviluppo e utilizzo delle Automazioni.
📕 Vedremo insieme alcuni esempi dell'utilizzo di Autopilot in diversi tool della Suite UiPath:
Autopilot per Studio Web
Autopilot per Studio
Autopilot per Apps
Clipboard AI
GenAI applicata alla Document Understanding
👨🏫👨💻 Speakers:
Stefano Negro, UiPath MVPx3, RPA Tech Lead @ BSP Consultant
Flavio Martinelli, UiPath MVP 2023, Technical Account Manager @UiPath
Andrei Tasca, RPA Solutions Team Lead @NTT Data
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
SAP Sapphire 2024 - ASUG301 building better apps with SAP Fiori.pdfPeter Spielvogel
Building better applications for business users with SAP Fiori.
• What is SAP Fiori and why it matters to you
• How a better user experience drives measurable business benefits
• How to get started with SAP Fiori today
• How SAP Fiori elements accelerates application development
• How SAP Build Code includes SAP Fiori tools and other generative artificial intelligence capabilities
• How SAP Fiori paves the way for using AI in SAP apps
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
Welocme to ViralQR, your best QR code generator.ViralQR
Welcome to ViralQR, your best QR code generator available on the market!
At ViralQR, we design static and dynamic QR codes. Our mission is to make business operations easier and customer engagement more powerful through the use of QR technology. Be it a small-scale business or a huge enterprise, our easy-to-use platform provides multiple choices that can be tailored according to your company's branding and marketing strategies.
Our Vision
We are here to make the process of creating QR codes easy and smooth, thus enhancing customer interaction and making business more fluid. We very strongly believe in the ability of QR codes to change the world for businesses in their interaction with customers and are set on making that technology accessible and usable far and wide.
Our Achievements
Ever since its inception, we have successfully served many clients by offering QR codes in their marketing, service delivery, and collection of feedback across various industries. Our platform has been recognized for its ease of use and amazing features, which helped a business to make QR codes.
Our Services
At ViralQR, here is a comprehensive suite of services that caters to your very needs:
Static QR Codes: Create free static QR codes. These QR codes are able to store significant information such as URLs, vCards, plain text, emails and SMS, Wi-Fi credentials, and Bitcoin addresses.
Dynamic QR codes: These also have all the advanced features but are subscription-based. They can directly link to PDF files, images, micro-landing pages, social accounts, review forms, business pages, and applications. In addition, they can be branded with CTAs, frames, patterns, colors, and logos to enhance your branding.
Pricing and Packages
Additionally, there is a 14-day free offer to ViralQR, which is an exceptional opportunity for new users to take a feel of this platform. One can easily subscribe from there and experience the full dynamic of using QR codes. The subscription plans are not only meant for business; they are priced very flexibly so that literally every business could afford to benefit from our service.
Why choose us?
ViralQR will provide services for marketing, advertising, catering, retail, and the like. The QR codes can be posted on fliers, packaging, merchandise, and banners, as well as to substitute for cash and cards in a restaurant or coffee shop. With QR codes integrated into your business, improve customer engagement and streamline operations.
Comprehensive Analytics
Subscribers of ViralQR receive detailed analytics and tracking tools in light of having a view of the core values of QR code performance. Our analytics dashboard shows aggregate views and unique views, as well as detailed information about each impression, including time, device, browser, and estimated location by city and country.
So, thank you for choosing ViralQR; we have an offer of nothing but the best in terms of QR code services to meet business diversity!
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...
Molecular basis and mutation by umerfarooq
1. DNA: The molecular basis of mutations
Since mutations are simply changes in DNA, in order to understand how mutations work, you
need to understand how DNA does its job. Your DNA contains a set of instructions for
"building" a human. These instructions are inscribed in the structure of the DNA molecule
through a genetic code. It works like this:
DNA is made of a long sequence of smaller units strung
together. There are four basic types of unit: A, T, G, and C.
These letters represents the type of base each unit carries:
adenine, thymine, guanine, and cytosine.
The sequence of these bases encodes instructions. Some parts
of your DNA are control centers for turning genes on and off,
some parts have no function, and some parts have a function
that we don't understand yet. Other parts of your DNA are
genes that carry the instructions for making proteins — which
are long chains of amino acids. These proteins help build an
organism.
1
2. Protein-coding DNA can be divided into codons — sets of three
bases that specify an amino acid or signal the end of the protein.
Codons are identified by the bases that make them up — in the
example at right, GCA, for guanine, cytosine, and adenine. The
cellular machinery uses these instructions to assemble a string of
corresponding amino acids (one amino acid for each three bases)
that form a protein. The amino acid that corresponds to "GCA" is
called alanine; there are twenty different amino acids synthesized
this way in humans. "Stop" codons signify the end of the newly
built protein.
After the protein is built based on the sequence of bases in the gene, the completed protein is
released to do its job in the cell.
Types of mutations
There are many different ways that DNA can be changed, resulting in different types of
mutation. Here is a quick summary of a few of these:
Substitution
A substitution is a mutation that exchanges one base for another (i.e., a
change in a single "chemical letter" such as switching an A to a G).
Such a substitution could:
1. change a codon to one that encodes a different amino acid and
cause a small change in the protein produced. For
example, sickle cell anemia is caused by a substitution in the
beta-hemoglobin gene, which alters a single amino acid in the
protein produced.
2. change a codon to one that encodes the same amino acid and
causes no change in the protein produced. These are called silent
mutations.
3. change an amino-acid-coding codon to a single "stop" codon and
cause an incomplete protein. This can have serious effects since
the incomplete protein probably won't function.
Insertion
Insertions are mutations in which extra base pairs are inserted into a
new place in the DNA.
Deletion
Deletions are mutations in which a section of DNA is lost, or deleted.
2
3. Frameshift
Since protein-coding DNA is divided into codons three bases long,
insertions and deletions can alter a gene so that its message is no longer
correctly parsed. These changes are called frameshifts.
For example, consider the sentence, "The fat cat sat." Each word
represents a codon. If we delete the first letter and parse the sentence in
the same way, it doesn't make sense.
In frameshifts, a similar error occurs at the DNA level, causing the
codons to be parsed incorrectly. This usually generates truncated
proteins that are as useless as "hef atc ats at" is uninformative.
There are other types of mutations as well, but this short list should give
you an idea of the possibilities.
The causes of mutations
Mutations happen for several reasons.
1. DNA fails to copy accurately
Most of the mutations that we think matter to evolution are "naturally-occurring." For example,
when a cell divides, it makes a copy of its DNA — and sometimes the copy is not quite perfect.
That small difference from the original DNA sequence is a mutation.
2. External influences can create mutations
Mutations can also be caused by exposure to specific chemicals or
radiation. These agents cause the DNA to break down. This is not
necessarily unnatural — even in the most isolated and pristine
environments, DNA breaks down. Nevertheless, when the cell repairs
the DNA, it might not do a perfect job of the repair. So the cell would
end up with DNA slightly different than the original DNA and hence,
a mutation.
The effects of mutations
3
4. Since all cells in our body contain DNA, there are lots of places for
mutations to occur; however, some mutations cannot be passed on to
offspring and do not matter for evolution. Somatic mutations occur in non-
reproductive cells and won't be passed onto offspring. For example, the
golden color on half of this Red Delicious apple was caused by a somatic
mutation. Its seeds will not carry the mutation.
The only mutations that matter to large-scale evolution are those that can be passed on to
offspring. These occur in reproductive cells like eggs and sperm and are called germ line
mutations.
Effects of germ line mutations
A single germ line mutation can have a range of effects:
1. No change occurs in phenotype.
Some mutations don't have any noticeable effect on the
phenotype of an organism. This can happen in many situations:
perhaps the mutation occurs in a stretch of DNA with no
function, or perhaps the mutation occurs in a protein-coding
region, but ends up not affecting the amino acid sequence of
the protein.
2. Small change occurs in phenotype.
A single mutation caused this cat's ears to curl backwards
slightly.
3. Big change occurs in phenotype.
Some really important phenotypic changes, like DDT resistance
in insects are sometimes caused by single mutations. A single
mutation can also have strong negative effects for the organism.
Mutations that cause the death of an organism are called lethals
— and it doesn't get more negative than that.
Little mutations with big effects: Mutations to control genes
Mutations are often the victims of bad press — unfairly stereotyped as unimportant or as a cause
of genetic disease. While many mutations do indeed have small or negative effects, another sort
of mutation gets less airtime. Mutations to control genes can have major (and sometimes
positive) effects.
Some regions of DNA control other genes, determining when and where other genes are turned
"on". Mutations in these parts of the genome can substantially change the way the organism is
built. The difference between a mutation to a control gene and a mutation to a less powerful gene
is a bit like the difference between whispering an instruction to the trumpet player in an orchestra
versus whispering it to the orchestra's conductor. The impact of changing the conductor's
behavior is much bigger and more coordinated than changing the behavior of an individual
orchestra member. Similarly, a mutation in a gene "conductor" can cause a cascade of effects in
the behavior of genes under its control.
4
5. Many organisms have powerful control genes that determine how the body is laid out. For
example, Hox genes are found in many animals (including flies and humans) and designate
where the head goes and which regions of the body grow appendages. Such master control genes
help direct the building of body "units," such as segments, limbs, and eyes. So evolving a major
change in basic body layout may not be so unlikely; it may simply require a change in a Hox
gene and the favor of natural selection.
Mutations to control genes can transform one body part into another. Scientists
have studied flies carrying Hox mutations that sprout legs on their foreheads
instead of antennae!
5
6. A case study of the effects of mutation: Sickle cell anemia
Sickle cell anemia is a genetic disease with severe symptoms, including pain and anemia. The
disease is caused by a mutated version of the gene that helps make hemoglobin — a protein that
carries oxygen in red blood cells. People with two copies of the sickle cell gene have the disease.
People who carry only one copy of the sickle cell gene do not have the disease, but may pass the
gene on to their children.
The mutations that cause sickle cell anemia have been extensively studied and demonstrate how
the effects of mutations can be traced from the DNA level up to the level of the whole organism.
Consider someone carrying only one copy of the gene. She does not have the disease, but the
gene that she carries still affects her, her cells, and her proteins:
1. There are effects at the DNA level
2. There are effects at the protein level
6
7. Normal hemoglobin (left) and hemoglobin in sickled red blood cells (right) look
different; the mutation in the DNA slightly changes the shape of the hemoglobin
molecule, allowing it to clump together.
3.
4. There are effects at the cellular level
When red blood cells carrying mutant hemoglobin are
deprived of oxygen, they become "sickle-shaped" instead
of the usual round shape (see picture). This shape can
sometimes interrupt blood flow.
5. There are negative effects at the whole organism level
Under conditions such as high elevation and intense
exercise, a carrier of the sickle cell allele may occasionally
show symptoms such as pain and fatigue.
6. There are positive effects at the whole organism level
Carriers of the sickle cell allele are resistant to malaria,
because the parasites that cause this disease are killed
inside sickle-shaped blood cells. Normal red blood
cells (top) and
This is a chain of causation. What happens at the DNA level sickle cells
propagates up to the level of the complete organism. This example (bottom)
illustrates how a single mutation can have a large effect, in this
case, both a positive and a negative one. But in many cases, evolutionary change is based on the
accumulation of many mutations, each having a small effect. Whether the mutations are large or
small, however, the same chain of causation applies: changes at the DNA level propagate up to
the phenotype.
Mutations are random
Mutations can be beneficial, neutral, or harmful for the organism, but mutations do not "try" to
supply what the organism "needs." Factors in the environment may influence the rate of mutation
but are not generally thought to influence the direction of mutation. For example, exposure to
harmful chemicals may increase the mutation rate, but will not cause more mutations that make
7
8. the organism resistant to those chemicals. In this respect, mutations are random — whether a
particular mutation happens or not is unrelated to how useful that mutation would be.
For example, in the U.S. where people have access to shampoos with chemicals that kill lice, we
have a lot of lice that are resistant to those chemicals. There are two possible explanations for
this:
Hypothesis A: Hypothesis B:
Resistant strains of lice were Exposure to lice shampoo
always there — and are just actually caused mutations for
more frequent now because all resistance to the shampoo.
the non-resistant lice died a
sudsy death.
Scientists generally think that the first explanation is the right one and that directed mutations,
the second possible explanation relying on non-random mutation, is not correct.
Researchers have performed many experiments in this area. Though results can be interpreted in
several ways, none unambiguously support directed mutation. Nevertheless, scientists are still
doing research that provides evidence relevant to this issue.
In addition, experiments have made it clear that many mutations are in fact random, and did not
occur because the organism was placed in a situation where the mutation would be useful. For
example, if you expose bacteria to an antibiotic, you will likely observe an increased prevalence
8
9. of antibiotic resistance. Esther and Joshua Lederberg determined that many of these mutations
for antibiotic resistance existed in the population even before the population was exposed to the
antibiotic — and that exposure to the antibiotic did not cause those new resistant mutants to
appear.
The Lederberg experiment
In 1952, Esther and Joshua Lederberg performed an experiment that helped show that many
mutations are random, not directed. In this experiment, they capitalized on the ease with which
bacteria can be grown and maintained. Bacteria grow into isolated colonies on plates. These
colonies can be reproduced from an original plate to new plates by "stamping" the original plate
with a cloth and then stamping empty plates with the same cloth. Bacteria from each colony are
picked up on the cloth and then deposited on the new plates by the cloth.
Esther and Joshua hypothesized that antibiotic resistant strains of bacteria surviving an
application of antibiotics had the resistance before their exposure to the antibiotics, not as a result
of the exposure. Their experimental set-up is summarized below:
1. Bacteria are spread out on a plate, called the "original plate."
2. They are allowed to grow into several different colonies.
3. This layout of colonies is stamped from the original plate onto a new plate
that contains the antibiotic penicillin.
4. Colonies X and Y on the stamped plate survive. They must carry a mutation
for penicillin resistance.
5. The Lederbergs set out to answer the question, "did the colonies on the new
plate evolve antibiotic resistance because they were exposed to penicillin?"
The answer is no:
When the original plate is washed with penicillin, the same colonies (those in
position X and Y) live — even though these colonies on the original plate have
never encountered penicillin before.
9
10. So the penicillin-resistant bacteria were there in the population before they encountered
penicillin. They did not evolve resistance in response to exposure to the antibiotic.
By Umerfarooq Dogar b.s botany university of gujrat
10