Genetic recombination involves the breaking and rejoining of DNA to form new combinations of genes. It occurs primarily during meiosis through several types of recombination, including homologous recombination where DNA exchanges occur between similar DNA molecules. This increases genetic diversity and allows for traits to be mixed. Recombination benefits populations by generating variety among offspring and allowing deleterious genes to be removed without losing the entire chromosome. It has applications in cloning, mapping genes, and making transgenic organisms.
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.
Replication Introduction , DNA replicating Models , Meselson and Stahl Experiments , Circuler Model of DNA replication , Replication in Prokaryotes , Replication In Eukaryotes , Comparison Between Prokaryotes and Eukaryotes Replicaton and PCR (Polymerease Chain Reaction)
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.
Replication Introduction , DNA replicating Models , Meselson and Stahl Experiments , Circuler Model of DNA replication , Replication in Prokaryotes , Replication In Eukaryotes , Comparison Between Prokaryotes and Eukaryotes Replicaton and PCR (Polymerease Chain Reaction)
Genetic recombination (genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. The process occurs naturally and can also be carried out in the lab.
Exchange of genes between two DNA molecules to form new combinations of genes on a chromosome
contributes to a population’s genetic diversity (source of variation in evolution)
Recombination is more likely than mutation to be beneficial
Less likely destroy a gene's function
May bring together combinations of genes
Recombinant DNA Technology - In nature, gene transfers are rather imprecise, and
their range, in tenns of species involved, is remarkably limited. The above problems are
circumvented by the recombinant DNA technology. A recombinant DNA molecule is produced
by joining together two or more DNA segments usually originating from different organisms.
More specifically, a recombinant DNA molecule is a vector into which the desired DNA
fragment has been inserted to enable its cloning in an appropriate host. This is achieved by using
specific enzymes for cutting the DNA (restriction enzymes) into suitable fragments and then for
joining together the appropriate fragments (ligation). In this manner, a gene may be produced,
which contains the. coding region from one organism joined to regulatory sequences from
another organism; such a gene is called chimaeric gene. Clearly, the capability to produce
recombinant DNA molecules has given man the power and opportunity to create novel gene
functions to suit specific needs. Recombinant DNA molecules are produced with one of the
following three objectives: (1) to obtain a large number of copies of specific DNA fragments,
(2) to recover large quantities of the protein produced by the concerned gene, or (3) to integrate
the gene in question into the chromosome of a target organism where it expresses itself. Even for
the latter two objectives, it is essential to first obtain a large number of copies of the concerned
genes. To achieve this, the DNA segments are integrated into a self-replicating DNA molecule
called vector; most commonly used vectors are either bacterial plasmids or DNA viruses. All
these steps concerned with piecing together DNA segments of diverse origin and placing them
into a suitable vector together constitute recombinant DNA technology. The DNA segment to
be cloned is called DNA insert. Recombinant DNAs are introduced into a suitable organism,
usually a bacterium; this organism is called host, while the process is called transformation. The
transformed host cells are selected and cloned. The recombinant DNA present in such clones
would replicate either in synchrony with or independent of the host cell; the gene present in \'the
vector mayor may not express itself, i.e., direct the synthesis of concerned polypeptide. The step
concerned with transformation of a suitable host with recombinant DNA, and cloning of the
transformed cells is called DNA cloning or gene cloning. However, often DNA or gene cloning
is taken to include both the development of recombinant DNAs as well as their cloning in a
suitable host. Similarly, often the term recombinant DNA technology is used as a synonym for
DNA or gene cloning used in the broader sense. A rather popular term for these activities is
genetic engineering. A clone consists of asexual progeny of a single individual or cell, while the
process/technique of producing a clone is called cloning. As a result, all the individuals of a
clone have the same genoty.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
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.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
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.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
3. What Is Recombination?
Recombination is a process by which pieces of DNA are broken and
recombined to produce new combinations of alleles.
This recombination process creates genetic diversity at the level of genes
that reflects differences in the DNA sequences of different organisms.
In eukaryotic cells, which are cells with a nucleus and organelles,
recombination typically occurs during meiosis.
During the alignment, the arms of the chromosomes can overlap and
temporarily fuse, causing a crossover.
Crossovers result in recombination and the exchange of genetic material
between the maternal and paternal chromosomes.
As a result, offspring can have different combinations of genes than their
parents.
4. Genetic recombination
Genetic recombination is the production of offspring with
combinations of traits that differ from those found in either parent.
During meiosis in eukaryotes, genetic recombination involves the
pairing of homologous chromosomes. This may be followed by
information exchange between the chromosomes.
Recombination may also occur during mitosis in eukaryotes where it
ordinarily involves the two sister chromosomes formed after
chromosomal replication.
5. Types of recombination
A+ B+ C+
A- B- C-
A+
B+ C+A-
B- C-
Homologous
or general
A B C
D E F
A B
CD E
F
Site-specific
att
att l
att att
l integrase
Replicative
recombination,
transposition
A B C A B C
transposase
l
E. coli
6. Homologous recombination
Homologous recombination is a type of genetic recombination
in which nucleotide sequences are exchanged between two
similar or identical molecules of DNA. It is most widely used by
cells to accurately repair harmful breaks that occur on both
strands of DNA, known as double-strand breaks.
These new combinations of DNA represent genetic variation in
offspring, which in turn enables populations to adapt during
the course of evolution.
Homologous recombination is also used in horizontal gene
transfer to exchange genetic material between different strains
and species of bacteria and viruses.
7. Two Types of Homologous
Recombination.
Double-strand break repair (DSBR)
pathway (sometimes called the double
Holliday junction model) .
Synthesis-dependent strand annealing
(SDSA) pathway.
8. Holliday junction - corresponding strands of two aligned
homologous DNA duplexes are nicked and the nicked
strands cross over to pair with the nearly complementary
strands of the homologous duplex after which the nicks are
sealed.
9. Formation of Holliday Junction
Branch migration-4 strands exchange base
pairing partners
10. Resolution of Holliday
Junction occurs in 2
ways
1.The cleavage of the strands that did not
cross over exchanges the ends of the
original duplexes to form, after nick
sealing, traditional recombinant DNA
2.The cleavage of strands that
crossed over exchanges a pair of
homologous single-stranded
segments.
11. X-ray structure of the cross over event.
Electron micrographs
of intermediates in the
homologous
recombination of two
plasmids.
12. The complex of Rec B, Rec C and Rec D
proteins recognizes the ends of a double
stranded break, and travels along the DNA
until reaching the closest Chi site.
Rec D cleaves the backbone of one strand
And dissociates from the complex.
Rec BC continue to unwind the DNA beyond
the chi site creating a stretch of single
Stranded DNA.
13.
14. Site-specific recombination
Site-specific recombination, is a type of genetic recombination in which
DNA strand exchange takes place between segments possessing only a
limited degree of sequence homology.
Site-specific recombinases (SSRs) perform rearrangements of DNA
segments by recognizing and binding to short DNA sequences (sites).
15.
16. Replicative recombination
It is a type of recombination which generates a new copy of a
segment of DNA. Many transposable elements use a process of
replicative recombination to generate a new copy of the
transposable element at a new location.
It is seen for some transposable elements, shown as red rectangles,
again using a specific enzyme, in this case encoded by the
transposable element.
Step 1 - Replicative Integration
Step 2 - Resolution
18. Benefits of recombination
Greater variety in offspring: Generates new combinations of
alleles
Negative selection can remove deleterious alleles from a
population without removing the entire chromosome carrying
that allele
Essential to the physical process of meiosis, and hence sexual
reproduction
Yeast and Drosophila mutants that block pairing are also defective in
recombination, and vice versa!!!!
19. Application
Homologous recombination employs zinc finger nucleases to
boost genomic integration and shows their usefulness in
efficient genome modification.
Site-specific recombination systems are potent genome
modifiers.
DNA transposition-based strategies provide means to
generate single-copy insertions.
DNA Cloning Using In Vitro Site-Specific Recombination
Used to map genes on chromosomes - recombination
frequency proportional to distance between genes.
Making transgenic cells and organisms.
20. References
Molecular Biology of the Cell, 4th edition
Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith
Roberts, andPeter Walter.
New York: Garland Science; 2002.ISBN-10: 0-8153-3218-1ISBN-
10: 0-8153-4072-9
Lodish, H. (2008). Molecular Cell Biology. W. H. Freeman
The Mechanism of Conservative Site-Specific Recombination
Annual Review of Genetics
Vol. 22: 77-105 (Volume publication date December 1988)
DOI: 10.1146/annurev.ge.22.120188.000453
N L Craig
Editor's Notes
Meiosis is a form of cell division that produces gametes, or egg and sperm cells. During the first phase of meiosis, the homologous pairs of maternal and paternal chromosomes align.
Genes that are located farther apart on the same chromosome have a greater likelihood of undergoing recombination, which means they have a greater recombination frequency.
Both the RecD and RecB subunits are helicases, i.e., energy-dependent molecular motors that unwind DNA (or RNA in the case of other proteins). The RecB subunit in addition has a nuclease function.[5] Finally, RecBCD enzyme (perhaps the RecC subunit) recognizes a specific sequence in DNA, 5'-GCTGGTGG-3', known as Chi(sometimes designated with the Greek letter χ).
RecBCD is unusual amongst helicases because it has two helicases that travel with different rates[6] and because it can recognize and be altered by the Chi DNA sequence.[7][8] RecBCD avidly binds an end of linear double-stranded (ds) DNA. The RecD helicase travels on the strand with a 5' end at which the enzyme initiates unwinding, and RecB on the strand with a 3' end. RecB is slower than RecD, so that a single-stranded (ss) DNA loop accumulates ahead of RecB (Figure 2). This produces DNA structures with two ss tails (a shorter 3’ ended tail and a longer 5’ ended tail) and one ss loop (on the 3' ended strand) observed by electron microscopy.[9] The ss tails can anneal to produce a second ss loop complementary to the first one; such twin-loop structures were initially referred to as “rabbit ears.”