Question Submission 2

Mendel’s experiments and his interpretations of them are mathematically sophisticated. I would argue that this aspect of his work is notable in no small part because quantification is a critical component of what we consider good science today. In light of our in-class discussion about the historical variability of standards for good science, however, it makes sense to ask about the role of sophisticated mathematical arguments in mid-19th century biology. Advanced mathematics played little role in the best natural history work leading up to the era of Mendel and Darwin. In fact, one can identify cases where the best mathematical work relevant to biology worked at cross-purposes to the best biological theories; I specifically have in mind Lord Kelvin’s 1862 calculation of the age of the earth.

My question then is this: How much epistemic weight did mathematical argumentation exert on biology in the mid-19th century? Did it carry reductive implications, and given a Darwinian mode of inquiry that emphasized qualitative organization of phenomenological characteristics, might advanced mathematics have been considered by some to be irrelevant or even counterproductive to a clear biological understanding of nature?

In Gregor Mendel’s Experiments in Plant Hybridization, it is stated that there is evidence that the hybrids are not an intermediate form between the two parent species. Sometimes one parent’s characteristics are shown in a greater quantity in the offspring and it can potentially be impossible to decide who the other parent is. This experiment was done on plants but can be seen in humans too.
I recently read an article that says there are new studies being done that show that mother’s and father’s genes may not play equal roles in the features the fetus inherits. The theory is that imprinting occurs, which is when one parent’s gene is inactivated by the other’s gene. Scientists have found around 1,300 genes in which imprinting occurs. The gene’s shown to imprint are currently being seen in the brain and social behavior, but could more be found that deal with our characteristics (since there have been 1,300 genes found so far in which imprinting occurs)? I find this interesting because we have been taught for many years that Mendel figured out that we get half of our genes from each parent and things can really change if this theory about imprinting is really what is happening. Is the focus still going to be on dominant and recessive traits or is it going to move to the genes actually being expressed by each parent?

In every biology textbook from high school through college, Mendel is credited with devising certain biological laws of inheritance, namely, the law of segregation, and the law of independent assortment. However, Mendel’s original paper does not make any reference to laws of inheritance, though he clearly devised powerful statistical generalizations in certain contexts (i.e. no epistasis, no environmental interaction, non-quantitative or un-linked traits). It is clear from the latter parts of his paper, namely section 10, that Mendel worries about generalizing from his peas to other organisms. Furthermore, Mendel is uncertain about generalizing about peas alone. For example, he implies that his work does not exhaust everything that could have been done on peas. In particular, he did not study every single cross, taking into account every single character or every single variety. Does he think that because of this, he cannot generalize to laws even about the peas themselves?

On the other hand, Mendel seems to believe that he is doing something of general importance. In the introduction, Mendel implies that his work is important for understanding the “evolution” (understood as development for Mendel) of organic forms generally, not just peas. Now, it seems correct that Mendel was not concerned with inheritance per se, but the development of hybrids, as evidenced by his use of the word “evolution.” Even if he did not intend for laws of inheritance to come of his work, you could then question why he never came to laws of hybridization, taking into account the preparatory steps he took in part 1 of his paper. The answer may lie in the following quote, “That, so far, no generally applicable law governing the formation and development of hybrids has been successfully formulated can hardly be wondered at by anyone who is acquainted with the extent of the task, and can appreciate the difficulties with which experiments of this class have to contend. A final decision can only be arrived at when we shall have before us the results of detailed experiments made on plants belonging to the most diverse orders.” Then, even if we acknowledge that Mendel was not concerned with inheritance, have we still made an historical error in assigning to Mendel laws of hybridization or development? Is it more accurate to say that Mendel set out to create a model experiment to be emulated across several species? And, with this model Mendel believed that the true mode of hybridization development could be determined.

Considering how old the the dichotomy of "phenomenological/reductionism" is, how easily classifiable is Mendel? Specifically, throughout Mendel's "Experiments in Plant Hybridization" the use of literals as representations of transmittable characteristics seems to be either a desperate attempt to maintain a phenomenological perspective, or an extremely cautious approach to a "reductionist" explanation of what might "actually be going on". Granted, the "phenotype/genotype" dichotomy hadn't yet appeared, But Mendel himself says the following: "The expression "recessive" has been chosen because the characters thereby designated withdraw or entirely disappear in the hybrids, but nevertheless reappear unchanged in their progeny..." Doesn't Mendel's use of the term "recessive" imply something unobservable? Can the conclusions reached by Mendel point in any other direction than the existence of something unobservable to him? Does this not scream in one's face "There is something going on here that I can't OBSERVE!"?

My question this week was sparked while reading the Extinction section of the Fourth Chapter: Natural Selection in the Origin of Species and considering the response I got on my question last week.

butch037 said, in part:
"I think that less specialized individuals in principle are a better idea, but the nature of evolution is twords specialization."

Darwin talks about the high level of competition in similar forms of organisms in the Third Chapter: Struggle for Existence. The implications of these similar forms effectively pushing their evolutionary process along through competition with one another seems to be a severe risk that pays off rarely. I am not saying that the pay off once acquired is not worth the trouble. It seems to me that if an organism is becoming more and more successful in an environment and thus develops more like species in that environment this leads to a greater level of variation in that population. Furthermore, this population has a better chance of developing individuals with a beneficial mutation through the highly variated gene pool.
Is it not that a species develops until the population is so large and the variation possibilities of each subsequent generation so great that the species then has enough directions of evolution such that if a, say natural disaster, destroys a necessary resource (to certain individuals in the species) the species can still survive based on the fact that they are widely adapted?
AND isn't it true that these adaptations are the best of their kind for that species due to the competition within the species?
ie: one variation of a plant species, #1, grows extremely fast and thus can get more sunlight than another variation, #2, which grows more slowly. For #2 to survive it must develop a way to be more efficient with the sunlight it does get. So once each variation is specialized in rapid growth for #1 and efficiency for #2 is it not possible for the variations to combine and get the best of both worlds?

Sorry if the desired ideas aren't conveyed accurately but I am new to this branch of jargon :)

In Moore's discussion of 'Early Evidence for the Nuclear Control of Inheritance' he describes the reasoning which late 19th century biologists used to pinpoint the nucleus as the location of the inheritable material. In dealing with the huge disparity between the characteristics of the ovum and the sperm, these biologists isolated the nucleus as the only tangible similarity between the male and female germ cells. They believed that inheritance was equal between the mother and father and only the nucleus provided observable evidence of this equality.
Though this is true, and the nucleus does contain the chromosomes, it has also turned out to be a simplification and much recent work in genetics is focused on exploring the ways in which other aspects of the ovum and sperm affect inheritance. Issues in Epigenetics such as the 'maternal effect' consider the importance of the vast reserves of resources found within the ovum's cytoplasm which are passed on to the developing zygote and can lead to many variations in heritable traits. Is this an example of the importance of revision in scientific practice? One goal of science is to produce the most succinct, simple models, but doesn't this usually require a fair amount of contradiction and self-cannibalization later on down the line as more and more complexity needs to be accounted for? Oftentimes, doesn't it reach a point where these developments invalidate the original theories upon which they are based? I had a professor once who said that the most important words in science are 'except when', because whenever one attempted to say something definitive in science you always needed to say, 'except when' to account for the multitude of exceptions that always exist for any supposedly solid rule or law.

How was the reception of Darwinism and the development of biology affected by the reluctance of naturalists, morphologists, embryologists to accept natural selection as the means by which evolution occurs? It has been well document that Darwin's Origin was more effective at convincing his temporaries that the transmutation of species was a real and investigable phenomenon; than convincing them that evolution occurs by means of natural selection (Bowler, 2000). Further, was the study of heredity influential in this rejection given that investigators like Mendel focused on discrete traits. Much of the criticism against Darwinism was against gradualism and whilst most biologists came to accept transmutation by the 1870's they were skeptical of natural selection and many argued that evolution proceeds by sports or saltations. Biologists that Mivart had argued that traits must occur in saltations (hopeful monsters) because gradations would not be advantageous (what use is an appendage that is between a limb and a wing, he asked) ergo natural selection is not possible (claimed Mivart)

Darwin published "On the Origin of Species" in 1859, and Mendel published his "Experiments in Plant Hybridization" in 1865. Mendel was active in the scientific community, and it seems as though he would have likely heard of a paper as controversial as Darwin's. Also, Darwin's work would have had obvious implications for the work of Mendel. Is there any definitive evidence that Mendel did or did not read Darwin? If he did, is there evidence that Mendel's own experiments were influenced by Darwin's work?

Our handout titled “Explanation and Evolution Among the Greeks” separates Mendel from Aristotle, saying that his views fall under the reductive umbrella. After completing the reading on Mendel’s plant hybridization is seems to me that his focus and intent of the experiments were much more aligned with phenomenological theory. He states: “The object of the experiment was to observe these variations in the case of each pair of differentiating characters and to deduce the law according to which they appear in successive generations.” The focus seems to be on blending inheritance, and observing situations where a white and red flower reproduce and create a pink flower, rather than on the unobservable genetics occurring to facilitate these physical changes. The general observation of the physical results of blending inheritance seems phenomenological in nature. Were Mendel’s plant hybridization experiments focused on genetics, and therefore reductive? Or would they be phenomenological? Would that make Mendel a scientist who followed phenomenological theories and happened to stumble across of science highly-reductive?

Question Submission Week 2:

Wilhelm Roux makes many different asumptions pertaining to mitotic division and the mechanism that is used in creating the resulting daughter cells. On page 50 Roux argues that the "primary division" must take place by itself (while the following divisions will follow certain mechanical devices). First off, when discussing the primary division Roux states that the simplest form for the purpose of the primary division will be division on a one-layered plane.
What does Roux mean by a one-layered plane?
For the secondary division Roux argues that inteligent mechanisms help in the split of the cell. He brings up the ability of the halves of the "qualities" to reciprocally repel each other. My second question is as follows:
Does Roux explain the origin of the reciprocal repulsion?
-Or is he just assuming it as a potential mechanism for the split?

There is a striking difference in process between Darwin and Mendel, though both scientists were conducting their research at roughly the same time. Mendel's experiment and mathematical stress is absolutely opposed to Darwin, whose argument rests on little or no direct experimental evidence (which is not to say it is any less effective). My question, then, is mainly historical: was Mendel considered a biologist at his time? Or did heredity and biology merge after Darwin's work, which suggests a very clear connection? This could not only explain the difference in scientific approach, but also explain why Darin and Mendel may not have been exposed to each others' work. Perhaps the almost mathematical nature of Mendel's work suggested a clear separation from Darwin's naturalism at the time.

Blending inheritance is the idea that the offspring of two people are essential a combination of the parents. An example is if one tall person and one short person were to have a child, the child would be of a medium stature. Darwin, in his first addition of The Origin of Species, believed in blending inheritance. The problem with this theory is that if blending inheritance were true, the population would eventually all end up with the same characteristics. The entire population would eventually converge upon a single numerical value for height. To me, this theory seems like something Darwin would have had a problem with because of its eventual outcome in nature. Where in nature does Darwin think he has evidence that blending inheritance occurs? Even after it is pointed out to him by Jenkins and Fisher that blending inheritance isn´t logical, why did he still think it was important for his theory? When he takes it out of The Origin of Species in later additions, does his text still have strong support for evolution even without blending inheritance as a factor?

Sept. 20 2010
In Chapter 2 of Heredity and Development, “The Cellular Basis of Inheritance”, Moore discusses ‘cell theory’ and how its realization in the mid 17th century was critical to understanding the actualities of the nature of biological heredity. And such that is true with all credited scientific theories, cell theory is viewed as fact, serving as foundation to countless perspectives and theories of biology.
But if cell theory is to be true, where did the first few living cell come from? Certainly not form another living cell, for no cell existed prior to the existence of that first cell.
The study of abiogenesis attempts to explain the existence of living cells as being the product chemical reactions unrelated to life of inanimate compounds. Abiogenesis was made made famous when Miller and Urey successfully synthesized amino acids by subjecting basic organic compounds to conditions hypothesized to be similar to the expream conditions of an early Earth. The Miller-Urey experiment seems to directly contradict cell theory. I guess the way to get around this contradiction is to conclude that all cells, excluding first cell or first few cells, come from other cells.
But extreme conditions similar to those found on the young Earth exist all around the world. So who is to say that in some extream environment, maybe on the brim of volcanic vents deep beneath the ocean surface and located in a far from explored area, life has been created, or is being created, apart from the common accepted lineage of heredity? My question is: Can we be completely certain of the validity of cell theory?

Previously, in Origin of Species, Darwin emphasized the popularity of the categorization of different species and varieties. In this endeavor, as well as in the study of heredity, it seems as though scientists were focused on observable differences. However, in chapter 2 of Heredity and Development (The Cellular Basis of Inheritance), Moore gives a historical account of the discovery of cells and their function. The theory that the scientists mentioned by Moore seemed to be working toward is a unified theory that all organisms (plants and animals alike) have cells with nuclei.

What created this shift in scientific research from seeking out and categorizing differences to looking for uniformity among all organisms?

In class was discuss the importance of Mendel’s work regarding to the
variation among species. It was also explain the importance of model
organisms and the reasons why Mendel choose peas as a organisms for his
experiment. What could happened is Mendel would choose another organism?
And what other model organism at that time would fit Mendel’s purpose?

In Moore, when discussing the continuity of cells, it seems that scientists encountered the problem of an infinite regress. The premise that each cell should come from a pre-existing cell leads to the need to identify the first cell. Here, Rudolf Virchow coined the “all cells from cells” and alludes to a cellular regress back to the beginning of life. Did scientists, particularly Virchow, have any notion or theory of the beginning of life? Or did cell theory spur on further questions of the nature and origins of existence. And perhaps still further, would the cell not take on the significance of being the key to understanding the origins of existence?

Moore makes it extremely clear that Walther Flemming is to be credited with having provided a great deal of understanding to the mechanics of what we now understand to be mitosis. Flemming's empirical observations, along with his instance that living cells be the "basis of reference" against which all structures observed in stained samples must be checked against, yielded previously unknown information on the behavior of cells during division.

However, in Moore's presentation of this material, it would seem to be the case that the conceptual understanding of what exactly was taking place during this cell division in terms of the substance of "granules" or chromosomes takes place with a separate cast of characters entirely. This second group of scientists include Haeckel, Roux, and Boveri--and I am having some trouble understanding how the two threads of scientific development connect up with one another. It seems to be the case that there is a historical narrative that has to do with Haeckel's "lucky guess" that the nucleus contained some sort of heritable material, Roux's understanding of the necessity of the type of division that occurred in mitosis for preserving what he called the "individual quality" of each granule, and Boveri's work with sea urchins that provided empirical evidence for chromosomes as heritable material.

How does this thread of development concerning the conceptual understanding of the vehicles of heredity connect with the aforementioned thread of development concerning the mechanics of these vehicles in cell division? Perhaps I have over-simplified a more complex series of events in this particular time in the history of science?

During lecture last Thursday, someone brought up the fact that Mendel isn't necessarily a geneticist. After reading Gregor Mendel's Experiments on Plant Hybridization, I have to say that I'm a little confused about whether or not Mendel was indeed into genetics. Mendel's experiments focused on the hybridization of pea plants, which dealt with crossing two parental pea plants to come up with a hybrid of the two. To me it sounds like Mendel was on the path to genetics, since genetics deals with the passing of traits to offspring. Mendel even used words like "recessive" and "dominant" in his paper. Recessive and dominant genes are talked about in genetics. Should Mendel be considered a geneticist? If not, what should we label Mendel as? The scientific world has labeled Mendel as the "father of genetics". It seems interesting that if Mendel wasn't into genetics that he would be labeled the father of it.

While Mendel’s work with pea plants was undoubtedly important to the pioneering concepts of genetics, Mendel himself was interested in the science of hybridization. As a result of this, he designed his experiment using plants that would best display dominant traits in order to secure an unambiguous scoring system in his generational tallies. While this was an acceptable thing to do in the context of a hybridization study, it is somewhat misleading in the context of genetics, which is what Mendel’s work is often attributed to. Although his findings, in conjunction with the Chromosome Theory of Inheritance, paved the way for the idea of genetic inheritance, we now know that a majority of mammalian characteristics including height, weight, eye color, certain diseases and many behaviors are polygenic traits, i.e. traits that are affected by multiple genes in varying amounts. While polygenic traits can be explained by the Chromosome Theory of Inheritance and its applications, they are somewhat inapplicable with Mendel’s concepts. With that being said, just how significant were Mendel’s contributions to the current understanding of how genes operate? Was his experimental setup designed in such a way that allowed his findings to be applied to non-hybridized plant species? Is Mendel a prime example of how historical conditioning can interfere with the true legacy of a scientist and his work?

I was troubled by one thing Professor Wimsatt said last week; "assume true-breeding is observable." It was proposed that you can tell if an individual is true-breeding for a particular trait after the F2 generation. That can't prove for certain that it's true-breeding, can it? Also, doesn't the idea of true-breeding rely on some sort of fixity, if not of species than of traits? Wouldn't all traits vary over generations? I am unclear as to what "true-breeding" is supposed to entail exactly. Most definitions say that true-breeding organisms can only produce identical offspring when paired with another true-breeding individual? That would entail that the pair is identical (which seems impossible to be exactly identical) and how could you know that they couldn't possibly produce any other type of offspring without conducting an infinitely long experiment?

My question is spawned from Mendel's Experiments in Plant Hybridization. There is a mention that although an offspring is created from two parent organisms it does not mean that the traits the offspring show will be a exact split of the original organisms. It is true that one parent can influence the offspring in a greater manner by having its genes dominate the other parent and make themselves more obviously displayed. Mendel shows this in plants but it is apparent in all forms of life. If a parent is going to dominate the genes of a offspring what is it that makes it the dominant trait. Is it a definite that this is the better of the two traits and that nature in its course of action has decided it knows which is more advantageous in the life of the offspring? Is there a factor of luck and percentage of likeliness? It would seem that nature is ever developing and evolving but with its imperfections and variance life is a gamble. I can best relate this to gambling to poker. Although I know the percentage odds of occurrence and what should happen there is always a chance that things are not going to happen in an expected manner. Is this the same with life, and if so does an amount of uncertain randomness improve a species evolution and odds of survival?

I found this question very interesting because it looks at the significance of the link between mathematics and science, particularly evolution. Today, we consider mathematics to be synonymous with science. You are expected to have a firm understanding of math in order to have a firm understanding of scientific principles. Yet, as Joe so eloquently pointed out, many of the most successful scientific philosophers had very little knowledge of mathematics. It does leave one to ponder, is it necessary to use math as a means to discover new scientific theories? As I see it, there is no one correct answer. That being said, Darwin wasn't working with genetics in the same fashion as modern day geneticists are. It is difficult for me to imagine modern day geneticists understanding the human genome as they do without understanding the mathematics behind the science.

Mendel's generalizations about hybrid development in peas depend on a true breeding parental generation. A question arose as to whether any of his pea plants really could have been shown to be true breeding after the F2 generation. First, true-breeding means that for a given trait, an individual is homozygous. Assuming that we have a 2 alleles for a trait (one dominant, one recessive as is the case for the traits that Mendel studied), this means that the offspring of this individual can only receive one of the two possible alleles segregating in the population from the parent, since the parent has 2 copies of the same allele (assuming the individual is diploid, as is the case with the peas). The question now becomes, knowing that the relationship between the two alleles is a dominate/recessive one, how do we distinguish a true - breeding homozygous dominant individual, from a heterozygous individual? After all, the observable phenotypes of these two will be exactly the same (assuming that there is no heterozygous effects, as seems to be the case with Mendel's peas).

Here, it is important to note that peas are self-crossing. The homozygous dominant individuals, when self-crossed, will produce homozygous dominant offspring (F1). The heterozygous individuals will produce 1 homozygous dominant, 2 heterozygous (exhibiting the same phenotype as the homozygous dominant) and 1 homozygous recessive. Of course, this is an idealized ratio. However, we can test whether the results deviate in a statistically significant way from the expected. Moving on, the heterozygous plant produces an offspring that has the recessive phenotype. In this way, we know that it is not true-breeding. But how can we be certain that the alleged homozygous dominant plant is true-breeding? First, the cross done in the parental generation produces many F1 offspring. It is a simple statistical inference that if it is not true-breeding, then we expect 25% of its offspring to exhibit the recessive phenotype. If it is true-breeding, then we expect none of the offspring to exhibit the recessive phenotype. So, when Mendel did not get any recessive phenotypes, he determined that his pea was true-breeding for that allele at that locus for that trait. There is no need for infinite generations of crosses, because there is no other way to get zero recessive phenotypes from a dominant phenotype, unless the dominant phenotype is homozygous dominant for that trait. With enough crosses and samples of offspring in a single generation, we can tell that the parent is true breeding. Again, there is a statistically acceptable range of deviation. To be sure, we do another self cross (of F1s) to make sure we have no strange statistical anomalies.

This says absolutely nothing about whether that allele is fixed in the population, because it is not a population level claim. The allele is fixed in that individual unless a mutation occurs. And, if a mutation popped up in the F1 generation, it would be visible in the F2 generation; we would get the 25% recessive phenotype. That mutated F1 would then be thrown out as not true-breeding, strengthening even more Mendel's identification of true-breeding individuals. If we don't need the trait to be fixed across all generations, we certainly do not need infinite generations. True-breeding implies that the individuals under investigation are homozygous. For that reason it is not necessary to entertain the fact that, down the line, mutations may pop up to call this into question. Mutations are visible, so when they don't appear, we are right to attribute true-breeding status to individual organisms.

I am also quite confused by this statement, it didn't make any sense to me so I decided to do some research. The information that I found was saying the same things stated in the question such as Mendel being considered "the father of genetics" and that he coined the terms dominant and recessive. Gregor was a scientist who gained his fame for developing the modern genetics. His work led to the discovery of inheritance, genotype and phenotype, and the concepts of homozygous and heterozygous. The only thing I came across was the fact that many of his peers did not appreciate his work and it wasn't accepted until it was rediscovered in the 1900s. The only thing that I can come up with is that these peers were the one's to not consider him a geneticist. I would also like to know more about this...so if someone knows more, I would like to hear!

Chris Perdoni wrote:
...just how significant were Mendel’s contributions to the current understanding of how genes operate? Was his experimental setup designed in such a way that allowed his findings to be applied to non-hybridized plant species? Is Mendel a prime example of how historical conditioning can interfere with the true legacy of a scientist and his work?

This, for me, points to some interesting issues with pinning down Mendel's legacy. Considering the reaction to Mendel's work from his contemporaries amounted to a deafening silence, we are perhaps more apt than usual to view his significance in terms of later work, such as modern genetics. Moore makes a statement to the effect that the history of genetics would not have been different if Mendel had never existed. Taking that to mean that he was not, in fact, important for contemporary or subsequent understanding of inheritance, what I take from Chris' observations is the general question: why study Mendel? I can envision a response to this question both from a historical perspective and a philosophical one.

Historical: Mendel, while not contributing to the conceptual development of biology, which would require other scientists to read and react to his work, provides some interesting historical lessons about scientific practice and communication. Because his work was ignored for so long, it's easy to conceive of Mendel as operating in a bubble, however, he had his own distinct path that led him to the experiments he did and the conclusions he reached, so it make sense to ask him what developments in natural history led him to ask the questions he did. Additionally, I don't think it's too presentist to ask why his work fell flat in the 1860s when it anticipated what we now consider to be landmark advances 40 years later.

Philosophical: This one is a bit easier. If we accept the conclusion from the above historical justification for studying Mendel, then he becomes a useful case study in mid-nineteenth century scientific practice. The way he designes his experiments, the evidence he takes as satisfactory, and the manner in which he draws his conclusions are then all relevant to our understanding of theory construction in the biological sciences.

It is interesting to point out that there could be a perceived “shift in scientific research from seeking out and categorizing differences to looking for uniformity among all organisms.” However, I think that no real shift necessarily had to or did take place. At the moment, I can think of two reasons for why this may be the case: 1) biology as a field was broadening and could easily sustain parallel taxonomic and cellular pursuits and 2) cellular theory, evolution and the classification of differences actually benefited from one another. Evolutionary theory needed some type of common denominator to function as a bridge to connect species with differing morphology to the same ancestors. In the discovery that essentially all life on Earth was comprised of cells, the cellular theory provided evolution with this common denominator. Taxonomy, in turn, was provided with an evolutionary structure that helped organize and explain the differences and similarities that we see on a morphological level.

There have been so many advances in genetics these days, that they are realizing that there are exceptions to mendels rule. For instance, in flowers, a white and a red rose can be bred to create a pink one. This is a form of blended inheritance where there is a dominant, recessive, and intermediate genotype. I remember learning about imprinting in genetics, and I think that as they discover more genes where imprinting occurs, more focus will be placed on what is expressed by each parent.

I Find this to be an interesting question because you are initially talking about how scientists were looking for observable differences, and then Moore brings up the fact that all living things have cells. This seems to make sense that he would do that, because if you can observe something and see that it is different from something else, there must be a blueprint that is causing observable differences among species. With this in mind I believe that by studying the cells I believe that scientists discovered that they were so called "blueprints" instilled in the cells that were causing genetic differentiation. In turn this would lead to the questioning of if all things came from one cell at a certain point, and then that cell could have possibly mutated creating new cells with different characteristics, which in turn points to a uniform theme among all living things.

I interpreted cell theory to mean that, after the origin of life, all cells arise from other cells. However, I don't know what the early cell theorists believed about this, and it would be interesting to find out what their theories were regarding the origin of life (if they had any). Also, I believe cell theory has been modified to account for this, that the first cell did not arise from a pre-existing cell. However, this doesn't account for the possibility of multiple origins of life.

I think the ideas you are dwelling on here are very interesting.
I believe that Mendel was worried about generalizing from his peas to other organisms because he understood the depth of the task he was involved in. Mendel's name, to me, has been placed next to things he may not have been all that concerned with. I think it may very well be the case that Mendel was trying to set up a model experiment, but I believe he did this to make sure that the experiment provided the most accurate results. So in this way, I would say Mendel was creating a model experiment to be emulated across several species. I think he was striving for truth first and foremost but he also understood that his model for seeking truth may be expanded, to incorporate say several species, which would lead to discoveries of new truths, say in the mode of hybridization development.

Brooke's Question:
In Gregor Mendel’s Experiments in Plant Hybridization, it is stated that there is evidence that the hybrids are not an intermediate form between the two parent species. Sometimes one parent’s characteristics are shown in a greater quantity in the offspring and it can potentially be impossible to decide who the other parent is. This experiment was done on plants but can be seen in humans too.
I recently read an article that says there are new studies being done that show that mother’s and father’s genes may not play equal roles in the features the fetus inherits. The theory is that imprinting occurs, which is when one parent’s gene is inactivated by the other’s gene. Scientists have found around 1,300 genes in which imprinting occurs. The gene’s shown to imprint are currently being seen in the brain and social behavior, but could more be found that deal with our characteristics (since there have been 1,300 genes found so far in which imprinting occurs)? I find this interesting because we have been taught for many years that Mendel figured out that we get half of our genes from each parent and things can really change if this theory about imprinting is really what is happening. Is the focus still going to be on dominant and recessive traits or is it going to move to the genes actually being expressed by each parent?

Be careful, it seems to me that there are two different things going on here. Mendel's work states that our genotype (what is in our genes) is equally determined by both parents. The article you read is related to phenotypes (how are genes are expressed). We are still receiving half of our genes from each parent; we are just not expressing them equally. This is not to down play the importance of the article, but I don't think that it will end up discrediting Mendel's work.

It's interesting to think about how the momentum shifted in the late 1800's from observational differences to similarities. I'm not sure any one thing 'created' this momentum shift, but it seems to be the byproduct of what was being sought after by the scientific community. In regards to Darwin's work and others with similar interests, the questions being addressed dealt with variation, speciation and phylogenetic progressions. Scientists who dealt with these topics were interested in observing the differences among organisms of the same species as well as across species. Thus, the focus was on observational differences. Moving ahead to the era described by Moore in Ch. 2, the questions being addressed were related to cytology. Scientists were interested in discovering how the cell worked and, more importantly, how it related to heredity and development. Once it was realized that all living things were comprised of these cells, it was logical to look for observational similarities - how all living things and their cells used the same types of mechanisms to reproduce and develop. So the shift from observational differences to observational similarities seems to be the result of a shift of scientific thought from evolutionary biology to cytology.

In response to Joe’s question, I think he makes a great point in understating and representing the fact that what we consider to be good science today differs from what was considered to be good science back when Mendel was working on his theory of inheritance and other theories and explanations of science and biology that were developed in the 19th century . But I also wound if, although the standards of science have changed (i.e. I don’t think that the notion of a double blind experiment existed in the time of Mendel), does that cast a shadow on the findings of Mendel, and moreover; the relevance of Mendel’s findings.
I believe that there no question that Mendel was on to something and, although I’m sure he did not fully understand the implications of his thinking, and although his methods may not survive the scrutiny of modern science, one cannot ignore the reality that Mendel bettered science’s understating of inheritance in such great magnitude that without him, we may be far behind in our understating of inheritance and genetics.