Chromatin is the complex combination of DNA and proteins that makes up chromosomes. It can be made visible by staining with specific techniques and stain (thus the name chromatin which literally means colored material). The major proteins involved in chromatin are histone proteins; although many other chromosomal proteins have prominent roles too. The functions of chromatin is to package DNA into smaller volume to fit in the cell, to strengthen the DNA to allow mitosis and meiosis and to serve as a mechanism to control gene expression and DNA replication.
It is the DNA located in the mitochondria.Mitochondrial DNA (mtDNA or mDNA) is the DNA located in the mitochondria.
They are double stranded circular DNA molecule.
It is only 16 kb in length – contains 16,600 bp.
It is haploid in nature.
It codes for 37 genes.
13 genes provide instructions for making enzymes involved in oxidative phosphorylation.
It is a process that uses oxygen and simple sugars to create ATP, the cells main energy source.
Chromatin is the complex combination of DNA and proteins that makes up chromosomes. It can be made visible by staining with specific techniques and stain (thus the name chromatin which literally means colored material). The major proteins involved in chromatin are histone proteins; although many other chromosomal proteins have prominent roles too. The functions of chromatin is to package DNA into smaller volume to fit in the cell, to strengthen the DNA to allow mitosis and meiosis and to serve as a mechanism to control gene expression and DNA replication.
It is the DNA located in the mitochondria.Mitochondrial DNA (mtDNA or mDNA) is the DNA located in the mitochondria.
They are double stranded circular DNA molecule.
It is only 16 kb in length – contains 16,600 bp.
It is haploid in nature.
It codes for 37 genes.
13 genes provide instructions for making enzymes involved in oxidative phosphorylation.
It is a process that uses oxygen and simple sugars to create ATP, the cells main energy source.
DNA is tightly packed in the nucleus of every cell. DNA wraps around special proteins called histones, which form loops of DNA called nucleosomes. These nucleosomes coil and stack together to form fibers called chromatin. Chromatin in turn forms larger loops and coils to form chromosomes.
DNA packaging is crucial because it makes sure that those excessive DNA are able to fit nicely in a cell that is many times smaller.
The DNA in bacterial cells are either circular or linear. To accommodate the size of bacterial cell, supercoiled DNA are folded into loops with each loop resembles shape of bead-like packets containing small basic proteins that is analogous to histone found in Eukaryotes.
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
DNA is tightly packed in the nucleus of every cell. DNA wraps around special proteins called histones, which form loops of DNA called nucleosomes. These nucleosomes coil and stack together to form fibers called chromatin. Chromatin in turn forms larger loops and coils to form chromosomes.
DNA packaging is crucial because it makes sure that those excessive DNA are able to fit nicely in a cell that is many times smaller.
The DNA in bacterial cells are either circular or linear. To accommodate the size of bacterial cell, supercoiled DNA are folded into loops with each loop resembles shape of bead-like packets containing small basic proteins that is analogous to histone found in Eukaryotes.
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
DNA, chromosomes and genomes Notes based on molecular biology of the cell. Biology Elite: biologyelite.weebly.com, please use together with the presentation
Cytogenetics_ Chromosmes_Dr Jagadisha T V_PPT.pptxJagadishaTV
●To study the structure of chromosomes.
● To understand the concepts of linkage and crossing over.
● To understand structural and numerical chromosomal aberrations.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
(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.
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 .
This pdf is about the Schizophrenia.
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1. CHROMATIN STRUCTURE
• Chromatin is composed of DNA and proteins, mostly basic proteins called histones
• That help chromatin fold so it can pack into the tiny volume of a cell’s nucleus.
• The two basic types of chromatin are
1. Euchromatin
2. Heterochromatin
2. EUCHROMATIN
• The chromatin fibres in this region are loosely coiled .
• Euchromatin undergoes the normal process of condensation and de condensation in the cell
cycle.
• Euchromatin constitutes the majority of the chromosomal material and is where most
transcription takes place.
3. HETEROCHROMATIN
• The chromatin fibres in this region are more tightly folded
• Heterochromatin remains in a highly condensed state throughout the cell cycle, even during
interphase.
• All chromosomes have heterochromatin at the centromeres and telomeres.
• In addition to remaining condensed throughout the cell cycle, heterochromatin is characterized
by a general lack of transcription.
4. HISTONES
Most eukaryotic cells contain five different kinds of histones: H1, H2A, H2B, H3,and H4.
These are extremely abundant proteins; the mass of histones in eukaryotic nuclei is equal to the
mass of DNA.
5. NUCLEOSOMES
• The total length of human DNA, if stretched out, would be
about 2 m, and this all has to fit into a nucleus only about 10
mm in diameter.
• In fact, if you laid all the DNA molecules in your body end
to end, they would reach to the sun and back hundreds of
times.
• DNA folding must occur in your body and in all other living
things. We will see that eukaryotic chromatin is indeed
folded in several ways.
• Eukaryotic DNA combines with basic protein molecules
called histones to form structures known as nucleosomes.
These structures contain four pairs of core histones (H2A,
H2B, H3, and H4) which wrapped a stretch of about 146 bp
of DNA.
6. 30-NM FIBER
• Nucleosomes fold on themselves to form a dense,
tightly packed structure that makes up a fiber with
a diameter of about 30 nm .
• Two different models have been proposed for the
30-nm fiber:
• A solenoid model, in which a linear array of
nucleosomes are coiled,
• Helix model, in which nucleosomes are arranged in
a zigzag ribbon that twists or supercoils. Recent
evidence supports the helix model
7. HIGHER-ORDER CHROMATIN FOLDING
• The next-higher level of chromatin structure is a series of loops of 30-nm fibers.
• On average, each loop encompasses some 20,000 to 100,000 bp of DNA and is about 300 nm in
length.
• The 300-nm loops are packed and folded to produce a 250-nm-wide fiber.
• Tight helical coiling of the 250-nm fiber in turn produces the structure that appears in metaphase
individual chromatids approximately 700 nm in width.