Earth's early atmosphere contained hydrogen and helium. After the Moon formed, volcanic activity produced CO, CO2, and water vapor. Once cyanobacteria evolved and performed photosynthesis, they consumed CO2 and produced oxygen. Currently, Earth's atmosphere is 78% nitrogen, 21% oxygen, and 1% trace gases. Burning fossil fuels adds excess CO2 and pollutants, warming the climate. CFCs have also depleted the ozone layer.
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 .
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.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
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.
Comparative structure of adrenal gland in vertebrates
Meteorology and Climate
1.
2. *Earth’s early atmosphere
contained lots of helium and
hydrogen.
*After the Moon formed, the
atmosphere contained CO,
CO2, and water vapor due to
repeated volcanic activity.
*Once early photosynthetic
life (cyanobacteria) was
introduced, it consumed the
carbon dioxide and
generated oxygen.
*Currently, Earth’s atmosphere
contains 78% nitrogen, 21.%
oxygen, and 1% trace gases.
3. *The burning of fossil fuels adds
extra CO2, which traps heat at
the surface and contributes to
global warming.
*Burning fossil fuels also adds
extra unburned hydrocarbons
like nitrogen and sulfur
oxides which pollute the
atmosphere.
*Man-made chemicals like
chlorofluorcarbons (CFC’s) in
aerosols and refridgerants
have decreased the ozone
concentration in the
stratosphere.
4. A. Reflected back into
space by different
particles in the upper
atmosphere.
B. Reflected by dust and
water droplets (clouds)
and scattered throughout
the troposphere.
C. Absorbed by the Earth's
surface and radiated out
as heat.
D.Absorbed by clouds.
E. Absorbed by the ozone in
the stratosphere.
5. *Winds are created by uneven
heat distribution at Earth’s
surface and modified by the
rotation of the Earth.
*Energy transfer between Earth’s
surface and the atmosphere
creates the weather.
*The Coriolis effect causes
deflections of the atmosphere
due to the rotation of Earth.
*On a weather map, isobars
indicate pressure differences.
Where the isobars are closer
together, the wind speeds will
be faster.
6. *Convection is the major
mechanism of energy
transfer in the oceans,
atmosphere, and Earth’s
interior.
*Convection in the
atmosphere is a major cause
of weather.
*When air is cooled at or
below its dew point and
condensation nuclei are
present, clouds can form.
7. *Warm air rises, condenses
and then clouds form.
*Condensation nuclei (ex.
dust) allow the water vapor
to condense.
*Cold fronts move very fast,
rapidly pushing up the warm
air and creating
cumulonimbus clouds.
*Along a warm front, the
warm air slides on top of the
colder air, creating many
miles of clouds ahead of the
front.
*Weather moves from west to
east across the U.S. due to
prevailing westerlies
8. Reading Pressure:
*If the first digit of the three
numbers is less than 5, put a
10 in front of the pressure
reading. Also put a decimal
point before the last digit.
*If the first digit of the three
numbers is greater than 5,
put a 9 in front of the
pressure reading. Put a
decimal point before the last
digit.
Example: 107 = 1010.7 mb
602 = 960.2 mb
Reading for Wind:
* The “arrow” tells you the
direction.
* The more “feathers”, the faster
the wind is blowing.
Reading Dew Point:
* Temperature that the air needs
to be for it to be saturated
(Holding moisture.)
9. * Both weather and
climate are
measurable and, to a
certain extent,
predictable.
* Instruments used:
1. Thermometer - air
temperature (degrees
Celsius)
2. Barometer - air pressure
(millibars)
3. Psychrometer - relative
humidity (given as a percent)
Weather
Instruments
10. *A tornado is a narrow, violent
funnel shaped column of spiral
winds that extends downward
from the cloud base toward
Earth.
*A hurricane is a tropical
cyclone (counterclockwise
movement of air)
characterized by sustained
winds of 120 kilometers per
hour (75 miles per hour) or
greater. Hurricanes need
warm moist air.
11. *Latitude: The higher the latitude, the colder the climate. The lower the
latitude, the warmer the climate.
1. Earth’s surface is much more efficiently heated by the Sun than is the
atmosphere.
2. The amount of energy reaching any given point on Earth’s surface is
controlled by the angle of sunlight striking the surface and varies with the
seasons.
3. Areas near the equator receive more of the Sun’s energy per unit area than
areas nearer the poles.
4. Only 50% of the Earth is receiving sunlight at one time.
*Elevation: The higher elevation (mountains), the colder the climate.
*Proximity to bodies of water: Water acts like a “heat blanket”; ocean
currents will influence the air temperatures.
