The document summarizes key information about C. elegans as a model organism for biological research. C. elegans is a small roundworm with a simple nervous system that is transparent and easy to grow in labs. It was the first multicellular organism to have its entire genome sequenced, which revealed around 20,000 genes. C. elegans is well-suited for research in developmental biology, neuroscience, and other areas due to its invariant cell lineage and fully mapped connectome.
Gene regulation in eukaryotes in a nutshell covering all the important stages of gene regulation in eukaryotes at transcriptional level, translation level and post-translational level.
Cell cell hybridization or somatic cell hybridizationSubhradeep sarkar
What is Cell-Cell Hybridization?
History
More about Somatic cell Hybridization
Mapping of genes by somatic cell Hybridization
Hybridoma technology
Other Applications of Somatic Cell Hybridization
Introduction
About Drosophila
Genome of Drosophila
Life cycle
Differentiation
Development of Drosophila
* Embryonic development
* Dorsal -ventral and
* Anterior posterior development
* Body segmentation
* Homeotic gene
Conclusion
Reference
A knockout mouse is a mouse in which a specific gene has been inactivated or“knocked out” by replacing it or disrupting it with an artificial piece of DNA.
The loss of gene activity often causes changes in a mouse's phenotype and thus provides valuable information on the function of the gene.
Polytene chromosome with respect to historical basis, occurrence, structural organisation, bands and inter bands, puff are briefly stated for basic idea.
You may find this interesting understand the reason behind the gaint structure of these chromosomes.
This study material is a compilation of various sources such as text books, website etc...
Enjoy the process of Learning
Thank you
Introduction
Definition
History
Why are the transgenic animals being produced
Transgenic mice
Mice: as model organism
Methods of creation of transgenic mice
knock-out mice
Application of transgenic mice
Conclusion
References
GENE CLONING,ITS HISTORY, NEW ADVENT IN GENE CLONING, PCR IMPORTANCE ,APPLICATION OF GENE CLONING,STEPS OF GENE CLONING,Antisense technology,Gene cloning in agriculture,Somatic cell therapy,Role of gene cloning in identification of genes responsible for human diseases,Synthesis of other recombinant human proteins and recombinant vaccines
Gene cloning in medicine,Recombinant protein from yeast,Problems with the production of recombinant protein in E.coli ,Expression of foreign genes in E.coli,Production of recombinant protein ,PCR can also be used to purify a gene,Obtaining a pure sample of a gene by cloning,Why gene cloning and PCR are so important,The advent of gene cloning and the polymerase
chain reaction.
Gene regulation in eukaryotes in a nutshell covering all the important stages of gene regulation in eukaryotes at transcriptional level, translation level and post-translational level.
Cell cell hybridization or somatic cell hybridizationSubhradeep sarkar
What is Cell-Cell Hybridization?
History
More about Somatic cell Hybridization
Mapping of genes by somatic cell Hybridization
Hybridoma technology
Other Applications of Somatic Cell Hybridization
Introduction
About Drosophila
Genome of Drosophila
Life cycle
Differentiation
Development of Drosophila
* Embryonic development
* Dorsal -ventral and
* Anterior posterior development
* Body segmentation
* Homeotic gene
Conclusion
Reference
A knockout mouse is a mouse in which a specific gene has been inactivated or“knocked out” by replacing it or disrupting it with an artificial piece of DNA.
The loss of gene activity often causes changes in a mouse's phenotype and thus provides valuable information on the function of the gene.
Polytene chromosome with respect to historical basis, occurrence, structural organisation, bands and inter bands, puff are briefly stated for basic idea.
You may find this interesting understand the reason behind the gaint structure of these chromosomes.
This study material is a compilation of various sources such as text books, website etc...
Enjoy the process of Learning
Thank you
Introduction
Definition
History
Why are the transgenic animals being produced
Transgenic mice
Mice: as model organism
Methods of creation of transgenic mice
knock-out mice
Application of transgenic mice
Conclusion
References
GENE CLONING,ITS HISTORY, NEW ADVENT IN GENE CLONING, PCR IMPORTANCE ,APPLICATION OF GENE CLONING,STEPS OF GENE CLONING,Antisense technology,Gene cloning in agriculture,Somatic cell therapy,Role of gene cloning in identification of genes responsible for human diseases,Synthesis of other recombinant human proteins and recombinant vaccines
Gene cloning in medicine,Recombinant protein from yeast,Problems with the production of recombinant protein in E.coli ,Expression of foreign genes in E.coli,Production of recombinant protein ,PCR can also be used to purify a gene,Obtaining a pure sample of a gene by cloning,Why gene cloning and PCR are so important,The advent of gene cloning and the polymerase
chain reaction.
Genomics C elegan genome and model organismiqraakbar8
The C. elegans genome is about 100 million base pairs long and consists of six pairs of chromosomes in hermaphrodites or five pairs of autosomes with XO chromosome in male C. elegans and a mitochondrial genome. The genome contains an estimated 20,470 protein-coding genes.
1 What is the study systemGeneral information. E.g. What is a .docxhoney725342
1 What is the study system?
General information. E.g. What is a “cell line”? Include images.
1 Why would a researcher use this study system?
The particular features of this system that make it useful. E.g. cell lines allow the study of genetically identical cells in many labs
1 What type of research questions can this study system be used to help answer?
List a few examples of research questions or general areas of research that can be addressed using this system. Elaborate a little on each, so we understand what you mean.
1 How does a researcher typically use this system?
What are the logistics of it? E.g. basic information about how they culture and propagate cell lines.
1 What are the pros and cons of this study system?
List and briefly explain any drawbacks or caveats that we should be aware of, along with particular benefits E.g. mammalian cell lines need adequate facilities and resources to be propagated, but they also allow for the study of mammalian cellular systems in vitro instead of studying another eukaryote like yeast.
6.Are there alternatives or variations on this study system?
If you can’t use this particular study system, what are your options for alternatives? E.g. Use yeast as a representative of a eukaryotic cell.
1 What is a real example from primary literature of this study system being used?
Provide a brief summary of the research that used the study system of interest, including the main objective, basic methods used, the main results, and conclusions. Include an image of at least one figure or table, along with an explanation of what that figure/table illustrates. You must provide the complete citation of the paper and/or a link to the online paper.
8.List of sources and places where we can find more information.
Background
C. elegans: A Simple Multicellular Model Organism
Scientists worldwide conduct basic research to address gaps in our knowledge in the hopes that this information can serve humanity in the future. Basic biological research seeks to answer questions of such elementary cellular and organismal activities as how cells grow, divide, die, move, store and use energy, and communicate.
Scientists use model organisms in basic research to answer these questions because model organisms offer simplified cellular systems that reproduce quickly, are easy to maintain, and are cost efficient. For example,
if a DNA mutation is known to result in a neurological disorder, more data can be generated using a model organism such as C. elegans, which reproduces and matures every 2–3 days, rather than waiting for a human child to mature and show symptoms. Commonly used basic model organisms include S. cerevisiae (yeast), C. elegans (nematode), D. melanogaster (fruit fly), and M. musculus (mouse).
Despite the seeming lack of a relationship to human beings, these model organisms have helped researchers understand the basic cellular machinery underlying a host of human pathologies such as cancer, neurological disorders, ...
INTRODUCTION
ABOUT DROSOPHILA
PHYSICAL APPEARANCE
CELL BIOLOGY OF DROSOPHILA DEVELOPMENT
LIFE CYCLE
THE DROSOPHILA GENOME
UNUSAL FEATURES OF DROSOPHILA
SEX DETERMINATION
GENETIC MARKERS
DEVELOPMENT IN DROSOPHILA
CLEAVAGE
THE ORIGINS OF ANTERIOR-POSTERIOR POLORITY {GENES}
CHROMOSOME ABERRATIONS
CONCLUSIONS
REFERENCES
Caenorhabditis elegans is a tiny, free-living nematode found worldwide. Newly hatched larvae are 0.25 millimeters long and adults are 1 millimeter long. Their small size means that the animals are usually observed with either dissecting microscopes, which generally allow up to 100X magnification, or compound microscopes, which allow up to 1000X magnification. Because C. elegans is transparent, individual cells and subcellular details are easily visualized using Nomarski (differential interference contrast, DIC) optics.
C. elegans has a rapid life cycle and exists primarily as a self-fertilizing hermaphrodite, although males arise at a frequency of <0.2%. These features have helped to make C. elegans a powerful model of choice for eukaryotic genetic studies. In addition, because the animal has an invariant numbers of somatic cells, researchers have been able to track the fate of every cell between fertilization and adulthood in live animals and to generate a complete cell lineage. Researchers have also reconstructed the shape of all C. elegans cells from electron micrographs, including each of the 302 neurons of the adult hermaphrodite. Moreover, because of the invariant wild-type cell lineage and neuroanatomy of C. elegans, mutations that give rise to developmental and behavioral defects are readily identified in genetic screens. Finally, because C. elegans was the first multicellular organism with a complete genome sequence, forward and reverse genetics have led to the molecular identification of many key genes in developmental and cell biological processes.
The experimental strengths and the similarities between the cellular and molecular processes present in C. elegans and other animals across evolutionary time (metabolism, organelle structure and function, gene regulation, protein biology, etc.) have made C. elegans an excellent organism with which to study general metazoan biology. At least 38% of the C. elegans protein-coding genes have predicted orthologs in the human genome, 60-80% of human genes have an ortholog in the C. elegans genome, and 40% of genes known to be associated with human diseases have clear orthologs in the C. elegans genome. Thus, many discoveries in C. elegans have relevance to the study of human health and disease.
Menders experiments were conducted using garden peas. Why would human.pdfisenbergwarne4100
Menders experiments were conducted using garden peas. Why would humans be an awful
choice for an experimental organism (give at least 3 reasons)? Give an example of an animal that
would be better sorted for genetics experiments. In Mendel\'s experiments, a plant with purple
flowers was crossed with a plant having white flowers. Explain why white flowers disappeared
in the F_1 generation and reappeared in the F_2. Your pet rabbit has curly fur. After seeking
advice from a rabbit breeder, you learn that curly fur is a dominant trait, but you want to know
the precise genotype of your pet. Describe how you could find out. Describe the inheritance of
ABO blood types in humans and explain why individuals with type O are universal donors while
individuals with type AB are universal acceptors. Describe the nature vs. nurture debate. In your
explanation, give an example of a trait that is controlled entirely by nature and one that is heavily
influenced by both nature and nurture.
Solution
Answer:
1. Studying human genetics is unlike studying the genetics of any other organism. In many ways,
humans are very poor model organisms for genetics. Long generation times make for slow
progress when doing genetic crosses, which brings us to another problem with human genetics:
The inability to make controlled crosses.
So, any human geneticist that tried to make controlled human crosses would most likely be
considered a very disturbed criminal and not a brilliant scientist. Besides, humans usually only
have one child at a time, which makes it really difficult to generate numbers of offspring that can
achieve statistical significance. On top of all this, there\'s the issue of genetic manipulation. Key
genetic techniques, like mutation screening and transgenics, are completely off-limits to human
geneticists.
Drosophila melanogaster (Fruit fly) would be better suited as a model organism for genetics
experiments.
1. The relationship between fruit fly and human genes is so close that often the sequences of
newly discovered human genes, including disease genes, can be matched with equivalent genes
in the fly.
2. 75 per cent of the genes that cause disease in humans are also found in the fruit fly.
3. Drosophila have a short, simple reproduction cycle. It is normally about 8-14 days, depending
on the environmental temperature. This means that several generations can be observed in a
matter of months.
4. Fruit fly are small (3 mm long) but not so small that they can’t be seen without a microscope.
This allows scientists to keep millions of them in the laboratory at a time.
5. They are inexpensive to maintain in the laboratory.
6. They require a simple diet consisting of simple sources of carbohydrates (cornmeal) and
proteins (yeast extract).
7. The only care they need is having their food changed regularly (every 10-14 days at 25C or 5-
6 weeks at 18C).
8. Drosophila have ‘polytene’ chromosomes, which means that they are oversized and have
barcode-like banding patterns.
Facts about DNA
Eukaryotic chromosomes
Chemical composition of eukaryotic chromosomes
Histones
Non-histone chromosomal protein
Scaffold proteins
Folded fibre model
Nucleosome model
H1 proteins
Histone modification
Chromatosome
Higher order of chromatin structure
Mechanism of DNA packaging
Conclusion
Introduction
2. Thermoregulation
3. Vant Hoff equation
4. Temperature effect on cells
5. Extreme cold : resistance and death
6. Extreme heat : resistance and lethal death
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
Salas, V. (2024) "John of St. Thomas (Poinsot) on the Science of Sacred Theol...Studia Poinsotiana
I Introduction
II Subalternation and Theology
III Theology and Dogmatic Declarations
IV The Mixed Principles of Theology
V Virtual Revelation: The Unity of Theology
VI Theology as a Natural Science
VII Theology’s Certitude
VIII Conclusion
Notes
Bibliography
All the contents are fully attributable to the author, Doctor Victor Salas. Should you wish to get this text republished, get in touch with the author or the editorial committee of the Studia Poinsotiana. Insofar as possible, we will be happy to broker your contact.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
BLOOD AND BLOOD COMPONENT- introduction to blood physiology
c elegans genome, life cycle and model organism
1. C. elegans genome and its
life cycle
SUBHRADEEP SARKAR
M.Sc IN APPLIED GENETICS
2. Model organisms
A model organism is a non-human species that is extensively studied to understand
particular biological phenomena, with the expectation that discoveries made in the
organism model will provide insight into the workings of other organisms.
Model organisms are in vivo models and are widely used to research
human disease when human experimentation would be unfeasible or unethical.
Most model organisms share a set of common features that make them amenable to
study in the laboratory: They are generally small, easy, and inexpensive to rear in the
lab, and reproduce quickly and prodigiously.
In addition, the best genetic model organisms have small genome sizes, and many can
reproduce sexually, allowing researchers to cross-breed individuals of different
genotypes.
Beyond these common traits, most model organisms have one or several unique
attributes that make them ideal for a particular line of research.
For instance, zebrafish readily produce many large, transparent embryos, and are
therefore a favorite research subject for developmental biologists.
The roundworm,Caenorhabditis elegans, has a simple but nonetheless sophisticated
nervous system, and displays simple behaviors, such as movement, feeding, and
mating. These properties make it well suited for neurobiology and behavioral genetics.
3. Caenorhabditis elegans: Biology and Genome
• Caenorhabditis elegans is a free-living, transparent nematode
(roundworm), about 1 mm in length, which lives in temperate
soil environments.
• Research into the molecular and developmental biology of C.
elegans was begun in 1974 by Sydney Brenner and it has since
been used extensively as a model organism.
• The organism is transparent and easy for manipulation and
observation , feeds on bacteria ,cheaply housed and cultivated in
large number (1000 worms / petridish) in the laboratory .
• Most investigators grow C.elegans on agar-filled petridishes
that are covered with a lawn of bacteria.
4. Biology of c. elegans
• C.elegans is unsegmented, vermiform, and bilaterally symmetrical, with
a cuticle integument, four main epidermal cords and a fluid-filled
pseudocoelomate cavity.
• C. elegans has two sexes: hermaphrodites and males.
• Individuals are almost all hermaphrodite, with males comprising just
0.05% of the total population on average.
• The basic anatomy of C. elegans includes a mouth, pharynx, intestine,
gonad, and collagenous cuticle.
• Males have a single-lobed gonad, vas deferens, and a tail specialized for
mating.
• Hermaphrodites have two ovaries, oviducts, spermatheca, and a single
uterus.
• Eggs are laid by the hermaphrodite and development is completed
externally.
• Eggs are fertilized internally , either from sperm produced by
hermaphrodite or from sperm contributed by by a male.
5. Biology of c. elegans
• When self-inseminated the wild type worm lay about 300 eggs. When
inseminated by by a male , the number of eggs may exceed 1000.
• Hermaphrodites which self fertilize produce only hermaphrodites. When
hermaphrodites mate with males , 50% of the progeny will be male s and
50% will be hermaphrodites.
• After hatching (about 14 hrs. after fertilization ), they pass through four
Larval stages (L1–L4).
• When crowded or in the absence of food, C. elegans can enter an
alternative third larval stage called the dauer state.
• Dauer larvae are stress-resistant and do not age.
• Hermaphrodites produce all their sperm in the L4 stage and then switch
over to producing oocytes.
• At 20 °C, the laboratory strain of C. elegans has an average life span of
approximately 2–3 weeks and a generation time of approximately 4 days.
• C. elegans has five pairs of autosomes and one pair of sex chromosomes.
• Hermaphrodite C. elegans have a pair of sex chromosomes (XX); the
rare males have only one sex chromosome (X0).
6.
7.
8. C.elegans as a model organism
• C. elegans is studied as a model organism for a variety of reasons.
• It is a multicellular eukaryotic organism that is simple enough to be
studied in great detail.
• Strains are cheap to breed and can be frozen. When subsequently
thawed they remain viable, allowing long-term storage.
• In addition, C. elegans is transparent, facilitating the study of cellular
differentiation and other developmental processes in the intact
organism.
• Nematodes have a fixed, genetically determined number of cells, a
phenomenon known as eutely..The developmental fate of every single
somatic cell (959 in the adult hermaphrodite; 1031 in the adult male) has
been mapped out.
• These patterns of cell lineage are invariant between individuals, in
contrast to mammals where cell development from the embryo is more
largely dependent on cellular cues.
9. C.elegans as a model organism
• In both sexes, a large number of additional cells (131 in the hermaphrodite, most
of which would otherwise become neurons), are eliminated by programmed cell
death (apoptosis).
• Researchers who study apoptosis (programmed cell death) use C. elegans as an
experimental organism in the hope of finding treatments for certain types of
human cancers, such as leukemia. By studying apoptosis in C. elegans,
researchers hope to identify genes that switch-on cell death in cancer cells.
• C. elegans is one of the simplest organisms with a nervous system.
• In the hermaphrodite, this comprises 302 neurons whose pattern of connectivity
has been completely mapped out.
• Researchers have explored the neural mechanisms responsible for several
interesting behaviors shown by C. elegans, including chemotaxis,
thermotaxis,mechanotransduction, and male mating behavior.
10. C.elegans as a model organism
• A useful feature of C. elegans is that the function of specific genes can be
disrupted by by RNA interference (RNAi).
• Silencing the function of a gene in this way can sometimes allow a researcher to
infer what the function of that gene may be.
• The nematode can either be soaked in or injected with a solution of double
stranded RNA , the sequence of which is complementary to the sequence of the
gene that the researcher wishes to disable.
• RNA interference (RNAi) in C. elegans can also be done by simply feeding the
worms transgenic bacteria expressing RNA complementary to the gene of
interest.
• This strategy for gene loss of function experiments is the easiest of all animal
models, and thus, scientists were able to knock down 86% of the ~20,000 genes
in the worm, establishing a functional role for 9% of the genome
11. • C.elegans can be stored for a long term in the laboratory.
• A 15% glycerol solution is used for the freezing of C. elegans.
• Samples are cooled at 1°C per minute. Freshly starved young
larvae survive freezing best.
• About 35 to 45% of the worms stored in liquid nitrogen survive.
• The worms can also be stored at −80°C for over ten years, but
survival is not as great as for worms stored in liquid nitrogen at
−196°C.
•
12. Genome of C.elegans
• C. elegans was the first multicellular organism to have its genome
completely sequenced.
• The sequence was published in 1998 although a number of small gaps were
present; the last gap was finished by October 2002.
• C. elegans genome was sequenced using the clone-by-clone approach.
• The C. elegans genome size is l (9.7 x 107
base pairs or 97 Megabases)
• This is approximately 20 x bigger than that of E. coli and about 1/30 of that
of human
• The adult hermaphrodite has 959 somatic nuclei. Its gene density is about 1
gene/5kb.
• Introns are 26% of the genome.
• About 35% of C. elegans genes have human homologs.
• Remarkably, it has been shown repeatedly that human genes replace their C.
elegans homologs when introduced into C. elegans. Conversely, many C.
elegans genes can function similarly to mammalian genes.
• There are some large intergenic regions containing repetitive DNA
sequences.
• Many genes are arranged in operons. C. elegans and other nematodes are the
only eukaryotes currently known to have operons.
13. Genome of C.elegans
• There are 19,735 protein coding genes with 2685 alternative splice forms,
bringing the predicted protein count to 22,420 .
• The genome contains more than 16,000 RNA genes.
• In 2003, the genome sequence of the related nematode C. briggsae was also
determined, allowing researchers to study the comparative genomics of these
two organisms.
• Work is now ongoing to determine the genome sequences of more
nematodes from the same genus such as C. remanei, C. japonica and C.
brenneri.
• The official version of the C. elegans genome sequence continues to change
as new evidence reveals errors in the original sequencing .
• Most changes are minor, adding or removing only a few base pairs (bp) of
DNA.
• For example, the WS169 release of WormBase (December 2006) lists a net
gain of 6 base pairs to the genome sequence.
• Occasionally more extensive changes are made, as in the WS159 release of
May 2006, which added over 300 bp to the sequence.