Have you ever wondered who was the first to discover something, that experiment did, and with that logic did? For those who have studied biology have surely heard of Griffith experiment!
Frederick Griffith was a medical officer engaged in the study of the bacterium pneumoniae: Streptococcus pneumonia.
In 1928suggested that there was a transforming principle that did change a strain of bacterium to another! He took a strain of pneumococcus bacteria, called S (S = Smoth, smooth) producing bacterial colonies smooth and shiny, but highly infectious and a strain called R (R = rough), whose colonies are wrinkled but harmless. Well, what did he do?
There are two versions of the S strain, IIS and IIIS, and an occasional strain S can change in strain R, and never by IIR to IIIS. The two strains differed in that the S strain IIIS caused the death of infected mice, which occurred in mice infected with strain IIS.
He injected in mice a mixture of live bacteria IIR (non-virulent) and with the heat-killed bacteria of type IIIS. All mice were killed by live bacteria which drew type IIIS, bacteria that could not be created for type-specific mutations by IIR.
Griffith concluded that some bacteria were transformed by IIR components of bacteria IIIS, material that he called Transforming Principle.
Then there were many researchers who resumed his experiments to understand the cellular components that allows the transformation, experiments such as Avery, Hershey and Chase experiments which I'll discuss in the future.
The earth 4.5 billion years, and presumably life appeared between 3 and 4 billion years ago. How
did life I will talk about in another post, as it has created the DNA,
that union of fundamental molecules that transmit the information
necessary for life. Let's see what it looks like DNA. The structure was discovered in 1953 by J.Watson and F. Crick and with the help of R.Franklin. Unfortunately,
all we remember that the discovery was made only by the first two
scientists, but in reality much it is due to Franklin, who died before
receiving the Nobel personally along with his colleagues.The
DNA (deoxyribonucleic acid) is composed of monomers called nucleotides
from a pentose, the deoxyribose (red circle), a nitrogenous base (circle
rooster) and a phosphate group (green circle). The DNA has a double
helix shape, ie there are
two filaments that are wound connected to each other thanks to the
nitrogen bases, The two strands follow two opposite directions, calls
the 5 'and 3', which serve to give the direction to the processes in
which the DNA is involved, such as duplication and transcription. Consider a single filament and see how he is both chemically and its structure in space. The
nucleotides are linked together via the covalent bond between the
phosphate group of a nucleotide and the carbon of the other nucleotide,
called phosphodiester bond. The phosphate group (PO42-) is linked to the 5 carbon sugar, while the nitrogenous base is linked to the carbon 1.
The
nitrogenous bases are divided into two groups, purines and pyrimidines:
the first are the Adenine (A) and Guanine (G), the latter are the
Cytosine (C) and Thymine (T). These four nitrogenous bases do not join
to case, but may bind to each other only in accordance with the sequence obliged CG, TA. The
linear arrangement of these bases damage to the cell the information
that serves, in fact, a gene is composed of thousands of purines and
purimidine, and according as they are placed can give information or the
other.The DNA looks like in the image:
The base pairs are spaced apart by 3.4 nm, thus leading to the formation of two grooves, one major and one minor. The two grooves are very important for the binding of macromolecules necessary for the function of some processes.But it is disposed in the cell's DNA? Assuming
that in nature there are two types of cells, prokaryotic, without the
eukaryotic nucleus and with the nucleus, the DNA we find it grouped
within the cytoplasm in the first type of cells and always grouped in
the second type, but within a structure called the nucleus. I
voluntarily omitted because the viruses are "entities" particolari.M to
exist in nature other structures of DNA, both in circular form, as in
bacteria and mitochondria, the cDNA, but also snDNA A-DNA and B-DNA,
which present difference
in space of the grooves, as well as the Z-DNA which rotates clockwise
so, then in the opposite direction to DNA.ed other types that will speak
in the future
The
DNA is said to be supercoiled, ie wound on whether stessto thanks to
the proteins called histone and non-histone to form chromatin. All together to form the chromosome. In
practice, the DNA strand is wound atorno to the protein, like a yoyo to
form a kind of pearl necklace which in turn is raggruppatom called
nucleosome. But why evolution has led to what? Serves both to protect this group that the genetic material, which is huge. The nucleosome is arranged in a structure which we call chromosome, what we all know that in humans is in the form of X or Y.In
Nature there are other structures of DNA, both in circular form, as in
bacteria and mitochondria, but also A-DNA and B-DNA, which have
difference in space of the grooves, as well as the Z-DNA which rotates
clockwise, then in the opposite direction to the DNA.
In
the next post will describe the processes of replication, that is, as
the DNA is duplicated, the transcription process, that is, as mRNA
(messenger RNA) copies information for Ribosomes, the protein factories,
but also RNA and all the processes that occur in cell.
Have you ever wondered who was the first to discover something, that experiment did, and with that logic did? For those who have studied biology have surely heard of Griffith experiment!
