Abstract
This essay aims to explore several scientific issues: the relation between the burning of fossil fuels and its consequential unbalance of the carbon cycle and the increase of the greenhouse effect that follows it, causing a biosphere change with multiple deleterious effects, both on environments, species and life itself; understand how Darwin’s theory of Natural Selection explains the existence of different species of a being (such as lizards) in one same island; why, now in the Genetics area, a cell’s DNA is only visible during mitosis for being condensed, why “daughter cells”, in meiosis, all have unique genetic material, caused by the random distribution of the genetic content of the diploid original cell, why a couple that is type A and B (with AO and BO genotypes) have a 25% chance of having a child with type O blood (OO genotype), why mutations, depending on the DNA site where they are located and trait that this area codes for, may not be the cause of problems, and why a simple shock inducing a cell to divide is not possible for cell duplication, since the genetic material – DNA – is not duplicated in the first place.
Keywords: fossil, fuel, carbon, cycle, problems, Darwin, species, different, environment, DNA, mitosis, visible, interphase, invisible, meiosis, daughter, different, unique genetic content, blood type, A type, B type, AO genotype, BO genotype, O type, mutations, coding region, problems, scientific, shock, inducing, division, cell.
As stated in the question’s introduction, the carbon cycle keeps the carbon levels stable on the atmosphere and, this, on its turn, is meant to keep life conditions at their optimal and balanced level. When burning fossil fuels, these being composed by carbon molecules, there is an extra release of carbon to the atmosphere. Obviously, these extra carbon molecules will enter the cycle of carbon, unbalancing it, since their number will be bigger in comparison to the other gases that constitute the atmosphere that, in a whole, are meant to be in a certain proportion. Such proportion is now affected and destroyed by the excess of carbon.
Thus, it has underlying problems arising from it; what is meant by this is the referral to the greenhouse effect increase. The greenhouse effect is positive when such balance mentioned above is present, because it keeps the environment’s temperature stable and within values that keep the biosphere. When increased, this means the temperatures also become higher, which is the underlying cause of ice caps melting, severe alterations in ecosystems fauna and flora and the disappearing of species, and the unbalance of the ozone layer, which brings a whole new level of problems related to more UVA and UVB radiation reaching the atmosphere, which has obvious deleterious effect on living beings health and life itself.
How four species of lizards, closely related, came to be separate species on a Caribbean island (Darwin)
According to Darwin’s theory and studies, it is believed that different species, such as those of the lizards, descend from one common ancestral species of lizard. This would explain the part of those lizard species being all closely related: having one same ancestral original “father”, they would have evolved from this original lizard, keeping some of the original features that formed their close relation to one another.
Continuing with Darwin’s theory, it is also believed that that original species, having reached that Caribbean island, would have set in different parts of the island and, consequently, would have been exposed to different environments, characteristics, predators and food availability; this continued to happen throughout the generations of lizards.
According to Darwin’s theory of Natural Selection, the individuals of that original species who best fit on those different habitats, given some specific characteristics they would have presented, would have survived and assured their offspring, in detriment of others. Thus, those different specific characteristics among them that kept them as the most fit in the multiple different habitats they had on the same island, were passed on to the future generations and these underwent the same process. In the end, and after many generations of genetic passage of fit characteristics, which would be different according to the environment, the lizards that once descended from one same species are now the four different species of lizards.
Why isn’t the DNA visible during interphase and why it is only visible during mitosis
Interphase has been defined as the cellular “living” phase; in such phase, all the cellular activities are performed, involving DNA reading, transcription, protein synthesis, etc. For this to happen, the DNA has to be in its “relaxed” form – uncoiled – on which it is called the chromatin – thin threads of DNA, present on the nucleus and available for all kinds of functions. So, being uncoiled and disperse, it is not visible.
Therefore, that is why that is the case that is only becomes visible during mitosis, because when a cell undergoes mitosis it is dividing itself. For this, it needs to evenly distribute the duplicated DNA between the future new born cells. To achieve such, the DNA coils, tighter and tighter, into the form of chromosomes, which will, then, distribute equally the duplicated genetic material between the cells resulting from division. This very condensed state of the DNA, thus, is what makes it visible under the microscope. And since this condensed DNA only forms in mitosis, for the genetic distribution during cell division that is why it is the only phase when it is visible microscopically.
How, in meiosis, four “daughter cells” are genetically different from one another
Meiosis is a cellular process in which gametes are formed. In such process, a diploid cell, which contains duplicate number of chromosomes, one from the mother and another from the father, divides itself and the DNA of these duplicated chromosomes needs to be distributed in the four cells that form, in order for each one to have a copy of each chromosome. Such distribution needs to be equally made.
The DNA’s genes in this process are distributed randomly between the four daughter cells that are formed from the division, being now haploid cells – the gametes. Thus, each gamete has a unique combination of mother and father genetic material, not being equal between them, because of this shuffle that occurs during their formation on meiosis. This way, by this random shuffle and distribution, in equality always, of genes between the gamete cells that result from the meiosis of the original diploid cell, each one of the gametes will have their own combination of genetic material, not being the same between any of these cells.
Showing, with Punnett squares, concerning blood type, whether a type A female and type B male can have a type O child.
An individual with type A can be either AA or AO; the same way that a type B can be BB or BO. Thus, a female type A that is AO, together with a male type B that is BO have four different possibilities for blood type of their child, being one of the possible ones, a child with type O (type O being always OO).
In conclusion, if the individuals of a couple that will have a child have a genotype that contains both A and O, and B and O information, when forming the gametes, there is 25% chance that the masculine and feminine gamete that fuse both contain O information, giving way to a child who will have OO genotype, which results, finally in a type O phenotype.
Answering Gorinda if whether a mutation can ever not cause problems
Mutations occur when, at the reading of the DNA, there is a mistake and a base is read as if it was another one (e.g. ATACC is read as AGACC), or if a base or more are missing, or there is an addition of bases, etc. Of course, the rest of the process has also mistakes, but this may not be necessarily bad. It essentially depends on the area of the DNA where the mutation occurs.
For once, that mutation may occur in areas of the DNA that won’t cause any problem, like if it is a non-coding region, or, in another case scenario, the mutation may not change the end-protein being produced, since there is more than one single codon for the final various amino acids. On another point of view, the mutation may not result in a problematic phenotype. If the mutation is located on a gene that codes for hair or eye color, for example, the end result might be nothing more than a color change, which won’t have any deleterious effect for the organism.
Finally, there are mutations that can create even better phenotypes, features that will make that organism be more fit to his environment’s characteristics and enhance survival probabilities, together with the possibility of generating offspring. This is the basic principle of Natural Selection. These mutations will, so, benefit the organism in its habitat, increasing survival of those who have that phenotype and allowing their offspring to be in a bigger number, even surpassing the other individuals who didn’t have that phenotype. Further ahead, this mutated phenotype may even become the “normal” one.
So, in conclusion, mutations are not necessarily problem bringers to the organism.
Explaining Thomas why scientists can’t just shock the cell, having its nucleus intact, to begin its division.
When a cell is undergoing division, its genetic content – DNA – is first in a duplicated number to, then, start to divide. This way, each pair of cells that result from the division of the previous one has the exact same DNA and genome. They are perfect copies of the original one.
When inducing division on a cell by shock, having its nucleus intact, the DNA, or genetic material, is not in duplicated number. Thus, such shock-induced division will cause a tear of the genetic content in half for each cell. The originated cells from that division, having only half of the genetic content of the original one, aren’t not only perfect copies but also functional, because the genome is not complete for full transcription and protein synthesis of all the content that is necessary for the cell to live.
When talking about human cell cloning in particular, things become even more complex, because not only the DNA is not in duplicate number, it cannot be from the same parent, or from parents of the same sex. The human genome is formed by a half from the masculine parent and a half from the feminine and each of these halves are responsible for different kinds of genes, having some an intrinsic relation to the sexual chromosomes.
Thus, it would not be possible to clone these cells, by just inducing division by shock.
Conclusion
In conclusion, one has understood why the use and burning of fossil fuels unbalances the carbon cycle and how this carries severe problems, like the increase of the greenhouse effect, its deleterious influence on ice caps, the biosphere’s environments, disappearing of species by changes in their habitat and unbalance of the ozone layer. It was also understood how different species, closely related, can be found in one same island by analyzing Darwin’s theory of Natural Selection, that eliminates the less fit individuals of one original ancestral species and leaves the ones who have specific traits that allow them to survive and that, with time, will make those individuals form whole new sets of species.
Furthermore, now in the Genetics area, it was explained that DNA is only visible in mitosis, because of being condensed; that in meiosis the shuffle and random distribution of the genetic material is what makes the “daughter cells” to have each unique genetic content; that a couple that is type A and type B can originate a type O offspring by having the O in their genome (AO and BO genome), having a 25% chance of the child to inherit the O from both parents; that not all mutations cause problems, depending on the zone of DNA where they are placed or of what phenotype trait the zone codes for; and finally, that a cell with its nucleus intact cannot have its division induced by shock, because the lack of duplicated DNA would only cause the originated cells to have half of the genetic content, which is not viable for the cells to live at all.
References
Johnson, George, Losos, Johnathan. “Essentials of the Living World”. McGraw-Hill Education, 31st of August, 2012. 2nd of March 2013.
