Transposable elements are segments of DNA that can change their position within the genome. They are divided into two classes based on their mechanism of movement. Class 1 elements encode reverse transcriptase and form DNA copies from RNA transcripts. Class 2 elements encode proteins that directly move the DNA. Transposable elements in prokaryotes include insertion sequences (IS elements) and transposons, while eukaryotes also contain retrotransposons similar to retroviruses. Transposition can disrupt genes or regulatory sequences and cause mutations. McClintock's work with maize introduced the concept of mobile genetic elements controlling gene expression.
One of the first plausible models to account for the preceding observations was
formulated by Robin Holliday.
The key features of the Holliday model are the formation of heteroduplex DNA; the
creation of a cross bridge; its migration along the two heteroduplex strands,
termed branch migration; the occurrence of mismatch repair; and the
subsequent resolution, or splicing, of the intermediate structure to yield different
typesof recombinant molecules.
One of the first plausible models to account for the preceding observations was
formulated by Robin Holliday.
The key features of the Holliday model are the formation of heteroduplex DNA; the
creation of a cross bridge; its migration along the two heteroduplex strands,
termed branch migration; the occurrence of mismatch repair; and the
subsequent resolution, or splicing, of the intermediate structure to yield different
typesof recombinant molecules.
Basics of Undergraduate/university fellows
Transcription is more complicated in eukaryotes than in prokaryotes because
eukaryotes possess three different classes of RNA polymerases and because of the
way in which transcripts are processed to their functional forms.
More proteins and transcription factors are involved in eukaryotic transcription.
This presentation deals with DNA replication in mamalian mitochondria. Mammalian mtDNA is replicated by proteins distinct from those used for nuclear DNA replication. According to the strand displacement model, replication is initiated from two distinct origins, OH and OL.
SOS response was discovered by Miroslav Radman. It's a part of DNA repair system- synthesizes enzymes required for DNA repair. Cellular response to UV damage.
this presentation is about reproduction of bacteria also known as genetic recombination. it consist of three types i.e. transformation, transduction and conjugation.
Basics of Undergraduate/university fellows
Transcription is more complicated in eukaryotes than in prokaryotes because
eukaryotes possess three different classes of RNA polymerases and because of the
way in which transcripts are processed to their functional forms.
More proteins and transcription factors are involved in eukaryotic transcription.
This presentation deals with DNA replication in mamalian mitochondria. Mammalian mtDNA is replicated by proteins distinct from those used for nuclear DNA replication. According to the strand displacement model, replication is initiated from two distinct origins, OH and OL.
SOS response was discovered by Miroslav Radman. It's a part of DNA repair system- synthesizes enzymes required for DNA repair. Cellular response to UV damage.
this presentation is about reproduction of bacteria also known as genetic recombination. it consist of three types i.e. transformation, transduction and conjugation.
A transposable element (TE or transposon) is a DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genome size.
Transposition often results in duplication of the TE.
Barbara McClintock's discovery of these jumping genes earned her a Nobel Prize in 1983.
Transposable elements make up a large fraction of the genome and are responsible for much of the C-value of eukaryotic cells.
Transportable elements are DNA Sequences that move from one location in a chromosome to another within the same chromosome or into another chromosome.
These are DNA Sequences that move from one location in a chromosome to another within the same chromosome or into another chromosome.
These are DNA Sequences that move from one location in a chromosome to another within the same chromosome or into another chromosome.
These are also known as “Jumping genes”.
This presentation provides an overview of What is a transposon,different types of transposons, their mechanism of action, examples for each type of transposons, changes caused due to insertion of transposon into the target gene and applications of Transposons. They are controlling factors in gene expression. Jumping genes is a special area of interest in Genetic research.
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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.
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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.
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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
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DERIVATION OF MODIFIED BERNOULLI EQUATION WITH VISCOUS EFFECTS AND TERMINAL V...Wasswaderrick3
In this book, we use conservation of energy techniques on a fluid element to derive the Modified Bernoulli equation of flow with viscous or friction effects. We derive the general equation of flow/ velocity and then from this we derive the Pouiselle flow equation, the transition flow equation and the turbulent flow equation. In the situations where there are no viscous effects , the equation reduces to the Bernoulli equation. From experimental results, we are able to include other terms in the Bernoulli equation. We also look at cases where pressure gradients exist. We use the Modified Bernoulli equation to derive equations of flow rate for pipes of different cross sectional areas connected together. We also extend our techniques of energy conservation to a sphere falling in a viscous medium under the effect of gravity. We demonstrate Stokes equation of terminal velocity and turbulent flow equation. We look at a way of calculating the time taken for a body to fall in a viscous medium. We also look at the general equation of terminal velocity.
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3. General Features of Transposable Elements
1. Transposable elements are divided into two classes on the basis of their
mechanism for movement:
a. Some encode proteins that move the DNA directly to a new position or
replicate the DNA to produce a new element that integrates elsewhere.
This type is found in both prokaryotes and eukaryotes.
b. Others are related to retroviruses, and encode reverse transcriptase
for making DNA copies of their RNA transcripts, which then integrate at
new sites. This type is found only in eukaryotes.
2. Transposition is non- homologous recombination
4. Transposable Elements in Prokaryotes
3. Transposable elements can cause genetic changes by :
a. Inserting into genes.
b. Increase or decrease gene expression by insertion into
regulatory sequences.
c. Produce chromosomal mutations through the
mechanics of transposition.
Prokaryotic examples include:
a. Insertion sequence (IS) elements.
b. Transposons (Tn).
c. Bacteriophage Mu (replicated by transposition)
5. Insertion Sequences
1. IS elements are the simplest transposable elements found in prokaryotes
2. Encode only genes for mobilization and insertion of its DNA.
3. IS elements are commonly found in bacterial chromosomes and plasmids.
4. Prokaryotic IS elements range in size from 768 bp to over 5 kb.
5. The ends of all sequenced IS elements show inverted terminal repeats
(IRs) of 9–41 bp.
7. 6. Integration of IS elements may:
a. Disrupt coding sequences or regulatory regions.
b. Alter expression of nearby genes by the action of IS element
promoters.
c. Cause deletions and inversions in adjacent DNA.
7. When an IS element transposes:
a. The original copy stays in place, and a new copy inserts randomly into
the chromosome.
b. The IS element uses the host cell replication enzymes for precise
replication.
c. Transposition requires transposase, an enzyme encoded by the IS
element.
d. Transposase recognizes the IR sequences to initiate transposition.
8. Schematic of the integration of an IS element into chromosomal DNA
9. Transposons
1. Transposons are similar to IS elements, but carry additional genes, and
have a more complex structure. There are two types of prokaryotic
transposons:
a. Composite transposons carry genes (e.g., antibiotic resistance)
flanked on both sides by IS elements (IS modules).
i. The IS elements are of the same type, and called ISL (left) and
ISR (right).
10. Structure of the composite transposon Tn10
ii. Tn10 is an example of a composite transposon . It is 9.3 kb, and
contains:
(1) 6.5 kb of central DNA with genes that include tetracycline
resistance (a selectable marker).
(2) 1.4 kb IS elements (IS10L and IS10R) at each end, in an
inverted orientation.
11. b. Noncomposite transposons also carry genes (e.g., drug resistance)
but do not terminate with IS elements.
i. Transposition proteins are encoded in the central region.
ii. The ends are repeated sequences
iii. An example is Tn3 : 1. length is about 5 kb, with 38-bp inverted terminal
repeats 2. It has three genes in its central region:
(a) bla encodes β-lactamase, which breaks down ampiciliin.
(b) tnpA --- transposase, needed for insertion into a new site.
(c) tnpB ---- resolvase, involved in recombinational events needed for transposition
(not found in all transposons).
12. Bacteriophage Mu
1. Bacteriophage Mu (mutator) can cause mutations when it transposes. Its
structure includes:
a. A 37 kb linear DNA in the phage particle; central phage DNA and
unequal lengths of host DNA at the ends .
b. The DNA’s G segment can invert, and is found in both orientations in
viral DNA.
2. Mu integrates into the host chromosome: The Mu prophage now replicates
only when the E. coli chromosome replicates.
13. Transposable Elements in Eukaryotes
1. Rhoades (1930s) working with sweet corn, observed interactions between
two genes.
2. McClintock (1940s-50s), working with corn (Zea mays) proposed the
existence of “controlling elements” that regulate other genes and are
mobile in the genome.
a. Most studied are transposons of yeast, Drosophila, corn and humans.
b. Structure is very similar to that of prokaryotic transposable elements.
14. Transposons in Plants
1. Plant transposons also have IR sequences, and generate short direct target
site repeats.
2. Can insert into a gene and produce a mutant allele.
i. Autonomous elements, which can transpose by themselves.
Alleles produced by an autonomous element are mutable alleles,
creating mutations that revert when the transposon is excised from
the gene.
ii. Nonautonomous elements, which lack a transposition gene and
rely on the presence of another transposon to supply the missing
function.
Mutation by these elements is stable.
15. McClintock ---- “mobile controlling element” in wheat kernel
(1) The element is Ds (dissociation).
(2) Its transposition is controlled by Ac (activator) .
16. Ty Elements in Yeast
Ty elements share characteristics with bacterial transposons :
a. Terminal repeated sequences.
b. Integration at non-homologous sites.
Ty element is -----
a. 5.9 kb including 2 terminal direct repeats of 334 bp, the long terminal
repeats (LTR) or deltas (δ).
b. Each delta contains a promoter and transposase recognition sequences.
17. Drosophila transposons
It is estimated that 15% of the Drosophila genome is mobile!
a. The copia retro transposons : 5-100 widely scattered copies per
genome
i. All copia elements in Drosophila can transpose, and there are
differences in number and distribution between fly strains.
ii. Structurally, copia elements are similar to yeast Ty elements:
LTRs of 276 bp flank a 5 kb DNA segment.
18. b. P elements : cause hybrid dysgenesis, a series of defects
(mutations, chromosomal aberrations and sterility) that result from
crossing certain Drosophila strains
i. A mutant lab strain female (M) crossed with a wild-type male (P)
will result in hybrid dysgenesis.
ii. A mutant lab strain male (M) crossed with a wild-type (P)
female (reciprocal cross) will have normal offspring.
iii. Thus, hybrid dysgenesis results when chromosomes of the P male
parent enter cytoplasm of an M type oocyte, but cytoplasm from P
oocytes does not induce hybrid dysgenesis.
19. The model is based on the observation that the M strain has no P
elements, while the haploid genome of the P male has about 40 copies.
(1) The F1 of an M female crossed with a P male have P
elements inserted at new sites .
(2) P elements encode a repressor protein that prevents
transposase gene expression, preventing transposition.
(3) Cytoplasm in an M oocyte lacks the repressor, and so
when fertilized with P-bearing chromosomes, transposition
occurs into the maternal chromosomes, leading to hybrid
dysgenesis
20. Structure of the autonomous P transposable element found in Drosophila
melanogaster
21. SINEs (Short interspersed elements)
human SINE repeat (short interspersed sequence) or the AluI restriction site in its
sequence.
short (about 100-400 bp)
A single family of SINEs (ALU)
This family is the only active SINE in the human genome
22. SINEs (Short interspersed
elements)
A human case of a genetic disease, neurofibromatosis,
provides some evidence.
i. Neurofibromatosis (tumor like growths on the
body) result from an autosomal dominant mutation.
ii. In a patient’s DNA, an unusual sequence was
detected in one of the introns of the neurofibromatosis
gene.
iii. Longer transcript is incorrectly processed, removing
an exon from the mRNA and producing a
nonfunctional protein.
iv. Neither parent had this sequence in the
neurofibromatosis gene.
23. LINEs (Long interspersed elements)
(Li elements)
LINEs are one of the most ancient and successful inventions in
eukaryotic genomes
In humans, are about 6 kb long
encode two open reading frames (ORFs)
Most LINE-derived repeats are short, with an average size of 900 bp
- 1,070 bp
cases of hemophilia have been shown to result from newly transposed
Li insertions into the factor VIII gene. (Factor VIII is required for normal
blood clotting.)
24. Pseudogene
“false” genes , which look like real genes but have no apparent
function
Pseudogene is a DNA sequence that is nearly identical to that of
a functional gene, but contains one or more mutations, making
it non-functional
Much of the intron material in the genomes of organisms is
composed of recognizable pseudogenes.
Pseudogenes are the molecular remains of broken genes which
are unable to function because of lethal injury to their
structures.
The great majority of pseudogenes are damaged copies of
working genes and serve as genetic fossils that offer insight
into gene evolution and genome dynamics.
25. There are three main types of pseudogenes :
1. Processed Pseudogenes: Lack introns, have small flanking direct repeats
and a 3’ polyadenine tail
portion of the mRNA transcript of a gene is spontaneously reverse transcribed
back into DNA and inserted into chromosomal DNA.
Once these pseudogenes are inserted back into the genome, they usually
contain a poly –A tail, and usually have had their introns spliced out
2. Duplicated Pseudogenes : A copy of a functional gene may arise as a result
of a gene duplication event and subsequently acquire mutations that cause
it to become nonfunctional.
The loss of a duplicated gene's functionality usually has little effect on an
organism's fitness, since an intact functional copy still exists.
3. Disabled genes, or unitary pseudogenes :
Various mutations can stop a gene from being successfully transcribed or
translated, and a gene may become nonfunctional or deactivated if such a
mutation becomes fixed in the population.