Concepts of Evolution and DNA in Biology

Concepts of Evolution and deoxyribonucleic acid in BiologyBecause the fossil record did non exhibit Darwins predicted slow and gradual evolution with transitional forms, more or less paleontologists desire to find a possibility of evolution where, interpolates in populations might continue too rapidly to leave many transitional fossils (see Figure from Gould and Eldredge 1977 .In 1972, Gould and Eldredge proposed the theory of punctuated correspondence where most evolution takes place in miniscule populations over relatively rapid geological age periods. By simplification the numerical size of the transitional population and the number of years for which it exists, punctuated equilibrium greatly limits the number of organisms bearing transitional characteristics. Since many organisms be not fossilized, this increases the handlelihood that transitional forms would not be fossilized. One strength of this theory is that Gould and Eldredge claim it is predicted by population transmissibles. save what argon the implications of punctuated equilibrium? chthonic(a) punctuated equilibrium, species usually change little as, gradual change is not the formula state of a species. Large populations may experience, minor adaptive modifications of move effect through time still will rarely transmogrify in toto to something fundamentally new. This is called stasis. But small peripheral populations may put up for more change at a quicker rate. Gould argued that most macroevolutionary change takes place in such populations during speciation such that there is insufficient time for the transitional forms to be fossilizedSpeciation, the process of macroevolution, is a process of ramify. And this branching is so rapid in geological translation (thousands of years at most compared with millions for the duration of most fossil species) that its results should generally lie on a bedding plane, not through the thick sedimentary installment of a long hillslope.What is meant by phylogeny? Give an account on phylogeny of humans.Ans- The context of evolutionary biology is phylogeny, the connections between all groups of organisms as understood by ancestor/descendant relationships. Not only is phylogeny outstanding for understanding paleontology, but paleontology in turn contributes to phylogeny. more groups of organisms are now extinct, and without their fossils we would not capture as clear a picture of how modern life is interrelated. We express the relationships among groups of organisms through diagrams called cladograms, which are homogeneous genealogies of species.Phylogenetics, the acquisition of phylogeny, is sensation part of the larger field of systematics, which also includes taxonomy. Taxonomy is the science of naming and classifying the diversity of organisms.In humans- it is used to the designate of genes.In general, organisms chiffonier inherit genes in ii ways vertical gene enchant and horizontal gene transfer. Vertical gene transfer is the passage of genes from call down to offspring, and horizontal gene transfer or lateral gene transfer occurs when genes jump between unrelated organisms, a common phenomenon in prokaryotes. plane gene transfer has complicated the determination of phylogenies of organisms, and inconsistencies in phylogeny have been reported among specific groups of organisms depending on the genes used to construct evolutionary trees.Carl Woese came up with the three-domain theory of life (eubacteria, archaea and eukaryotes) ground on his seceribonucleic acidtey that the genes encoding ribosomal ribonucleic acid are ancient and distributed over all lineages of life with little or no horizontal gene transfer. Therefore, rribonucleic acids are commonly recommended as molecular(a) clocks for reconstructing phylogenies.This has been particularly useful for the phylogeny of microorganisms, to which the species concept does not adjudge and which are too morphologically simple to be classified tooshied on phenotypic traits.desoxyribonucleic acid is genetic material. Describe cardinal authoritative experiments to support this statement.Ans- Clarification came during the First World War. During the war, hundreds of thousands of servicemen died from pneumonia, a lung infection caused by the baceterium Streptococcus pneumoniae. In the early 1920s, a young British troops medical officer named Frederick Griffith began correctioning Streptococcus pneumoniae in his laboratory in the hopes of developing a vaccine against it. As so often happens in scientific research, Griffith never found what he was looking for (there is still no vaccine for pneumonia), but instead, he made one of the most important discoveries in the field of biology a phenomenon he called transformation.Dr. Griffith had isolated two pedigrees of S. pneumoniae, one of which was pathogenic (meaning it causes sickness or death, in this event, pneumonia), and one which was sinless or harmless. Th e pathogenic birdcall looked smooth under a microscope overdue to a protective coat surrounding the bacteria and so he named this touch S, for smooth. The harmless strain of S. pneumoniae lacked the protective coat and appeared rough under a microscope, so he named it R, for rough .Dr. Griffith observed that if he injected some of the S strain of S. pneumoniae into mice, they would get sick with the symptoms of pneumonia and die, patch mice injected with the R strain did not become sick. Next, Griffith noticed that if he applied to the S strain of bacteria, and then injected them into mice, the mice would no extended get sick and die. He thence hypothesized that excessive heat kills the bacteria, something that some other scientists, including Louis Pasteur, had already shown with other types of bacteria.However, Dr. Griffith didnt stop there he decided to try something he mixed living R bacteria (which are not pathogenic) with heat-killed S bacteria, then he injected the garland into mice. Surprisingly, the mice got pneumonia infections and eventually died (Figure 3).Dr. Griffith examined samples from these sick mice and saw living S bacteria. This meant that either the S bacteria came back to life, an unlikely scenario, or the live R strain was somehow transformed into the S strain. Thus, after repeating this experiment many times, Dr. Griffith named this phenomenon transformation. This discovery was signifi pottyt because it showed that organisms can somehow be genetically re-programmed into a slightly different version of themselves. One strain of bacteria, in this case the R strain of S. pneumoniae, can be changed into something else, presumably because of the transfer of genetic material from a donor, in this case the heat-killed S strain.Scientists around the initiation began repeating this experiment, but in slightly different ways, trying to discover exactly what was happening. It became clear that, when the S bacteria are killed by heat, t hey error open and many substances are released. Something in this mixture can be absorbed by living bacteria, leading to a genetic transformation. But because the mixture contains protein, RNA, DNA, lipids, and carbohydrates, the question remained which molecule is the transforming performer?This question was examined in some(prenominal) ways, most famously by three scientists working at The Rockefeller appoint (now Rockefeller University) in New York Oswald Avery, Colin MacLeod, and Maclyn McCarty. These scientists did almost exactly what Griffith did in his experiments but with the pursuance changes. First, after heat-killing the S strain of bacteria, the mixture was separated into six exam tubes. Thus, each of the test tubes would contain the unknown transforming agent. A different enzyme was then added to each tube except one the control which received nothing. To the other five tubes, one of the following enzymes was added RNase, an enzyme that destroys RNA protease, an enzyme that destroys protein DNase, an enzyme that destroys DNA lipase, an enzyme that destroys lipids or a combination of enzymes that break down carbohydrates. The theory behind this experiment was that if the transforming agent was, for example, protein the transforming agent would be destroyed in the test tube containing protease, but not the others. Thus, whatever the transforming agents was, the silver-tongued state in one of the tubes would no longer be able to transform the S. pneumonia strains. When they did this, the result was both dramatic and clear. The liquid from the tubes that received RNase, protease, lipase, and the carbohydrate-digesting enzymes was still able to transform the R strain of pneumonia into the S strain. However, the liquid that was treated with DNase completely lost the ability to transform the bacteria .Thus, it was apparent that the transforming agent in the liquid was DNA. To further demonstrate this, the scientists took liquid extracted fro m heat-killed S. pneumoniae (S strain) and subjected it to extensive preparation and purification, isolating only the polished DNA from the mixture. This pure DNA was also able to transform the R strain into the S strain and generate pathogenic S. pneumoniae. These results provided powerful evidence that DNA, and not protein, was in truth the genetic material inside of living cells.PART-BDo the two strands of DNA duplex carry the same genetic information? Explain.Ans- No,the two strands of dna duplex carry different information ,becausecomplementary demonstrate pairsbinding to form a bivalent whorl.The two chains are wound round each other and linked together by hydrogen bonds between specific complementary home bases to form a whirl ladder-shaped moleculeThe stabilization ofduplex( figure-stranded) DNA is also dependent on base stacking. The planar, rigid bases stack on top of one another, much like a stack of coins. Since the two purine.pyrimidine pairs (A.T and C.G) have the s ame width, the bases stack in a rather uniform fashion. Stacking near the center of the helix affords rampart from chemical and environmental attack. Both hydrophobic interactions andvan der Waals forceshold bases together in stacking interactions. About half the stability of the DNA helix comes from hydrogen bonding, while base stacking provides much of the rest.What is the difference between Z and B- DNAs?ANS- Z-DNAis one of the many possible restate helical structures ofDNA. It is a left-handed double helical structure in which the double helix winds to the left in a zig-zag pattern. alternatingpurine-pyrimidinesequence (especially poly(dGC)2), negativeDNA supercoilingor broad(prenominal) salt and somecations(all at physiological temperature, 37C, and pH 7.3-7.4). Z-DNA can form a junction (called a B-to-Z junction box) in a structure which involves the extrusion of a base pair.The Z-DNA conformation has been difficult to study because it does not exist as a stable feature of the double helix. Instead, it is a transient structure that is occasionally induced by biological activity and then quickly disappears.B-DNAIt is an antiparallel double helix.It is a right helix. The base-pairs are perpendicular to the axis of the helix. (Actually, they are very slightly atilt at an angle of 4 degrees)The axis of the helix passes through the concentrate on of the base pairs.Each base pair is rotated by 36 degrees from the side by side(p) base pair.The base-pairs are stacked 0.34 nm apart from one another.The double helix repeats every 3.4 nm, i.e. the pitch of the double helix is 3.4 nm.B-DNA has two distinguishable grooves a MAJOR groove and, a MINOR groove. These grooves form as a consequence of the fact that the beta-glycosidic bonds of the two bases in each base pair are attached on the same edge. However, because the axis of the helix passes through the centre of the base pairs, both grooves are similar in depth.6. What is the role of RNA in DNA replicatio n?ANS- RNA WAS NEED TO INTIATE THE TRANSCRIPTION PROCESS. On the lagging strand, primase builds an RNA primer in short bursts. DNA polymerase is then able to use the free 3 OH group on the RNA primer to synthesize DNA in the 5 3 direction. The RNA fragments are then removed (different mechanisms are used in eukaryotes and prokaryotes) and new deoxyribonucleotides are added to fill the gaps where the RNA was present. DNA ligase is then able to ligate the deoxyribonucleotides together, completing the synthesis of the lagging strand. This rna primer was a short strand of RNA that is synthesized along single-stranded DNA during replication, initiating DNA polymerase-catalyzed synthesis of the complementarystrand.