Gregor J, Mendel teorías | Guías, Proyectos, Investigaciones de Genética

Review Czech J. Genet. Plant Breed., 50, 2014 (2): 43–51

Gregor J. Mendel – Genetics Founding Father

Erik SCHWARZBACH 1, Petr SMÝKAL2, Ondřej DOSTÁL3, Michaela JARKOV SKÁ3

and Simona VALOVÁ4

1Miroslav, Czech Republic; 2Faculty of Science, Palacký University Olomouc,

Olomouc, Czech Republic; 3Mendel Museum and 4Faculty of Science, Masaryk University,

Brno, Czech Republic

Abstract

Schwarzbach E., Smýkal P., Dostál O., Jarkovská M., Valová S. (2014): Gregor J. Mendel – genetics found-

ing father. Czech. J. Genet. Plant Breed., 50: 43–51.

Mendel’s impact on science is overwhelming. Although based on the number of scientific papers he published he

might be considered a meteorologist, his most significant contribution is his study of plant hybrids. This single

work puts Mendel on a par with Darwin’s evolutionary theory and establishes him firmly in the frame of today’s

biology. The aim of this article is to introduce the personality of Gregor Johann Mendel, focussing not just on

his scientific work, but also on his background and what or who influenced him. To understand Mendel’s use of

quantification and mathematical analysis of obtained results, representing a radical departure from methods of

his predecessors, it is important to know something about their arguments, beliefs, and practices. He designed

his experiments to answer a long standing question of hybridization, not inheritance as we perceive it today,

since the science of genetics was born considerably later. He studied many genera of plants, but his famous

research was on garden peas. To choose a single species for his crosses was fundamental to his success, but

also fuelled most of criticism at the time he presented his results. The reason for his success was partly due to

being a hybrid himself: of a biological scientist, a physical scientist and a mathematician. Mendel’s other fields

of interest such as meteorology and bee keeping are also introduced in this article.

Keywords: heredity; hybridization; manuscript; Mendel; Pisum

Gregor Johann Mendel has left an indelible mark

on the history of science. His work together with

Darwin’s evolutionary theory established the theo-

retical basis of today’s biology. Many books have

been written about his life, and his discoveries are

recorded in almost every biology textbook. The

first Mendel biography by Hugo Iltis, 1924, “Gregor

Johann Mendel. Leben, Werk und Wirkung” (Iltis

1924), later translated to English (Iltis et al. 1932), is

the basic source of information about Mendel, even

today. Iltis collected historical documents connected

to Mendel and used them as source for his book. The

number of these historical documents is limited,

but it is not true, that, as often wrongly argued, his

personal belongings were burnt after his death. Any-

way, the discovery of new information about Gregor

Mendel is very rare and other authors can only refer

to, supplement or newly interpret what Hugo Iltis

documented. The latest book about Mendel, “Soli-

tude of a Humble Genius – Gregor Johann Mendel:

Volume 1” appeared in 2013 (Klein et al. 2013) and

took 10 years of preparation. Before commenting

Mendel’s work let’s look at some aspects of his life.

Mendel was born, according to the birth record, on

20th of July 1822 at the small village Heinzendorf bei

Odrau (then in the Silesian part of Moravia within

the Austrian empire, now Hynčice u Vražného in

northern Moravia in the Czech Republic) and was

baptized Johann the same day. However, according

to his nephew, Mendel celebrated his birthday the

22th of July. Contemporary speculations about his

nationality (German, Austrian, Silesian, Moravian,

Czech) overlook the fact that nationality in its present

day sense was barely important in his time. Mendel

Vista previa parcial del texto

¡Descarga Gregor J, Mendel teorías y más Guías, Proyectos, Investigaciones en PDF de Genética solo en Docsity!

Review Czech J. Genet. Plant Breed., 50, 2014 (2): 43–

Gregor J. Mendel – Genetics Founding Father

Erik SCHWARZBACH 1 , Petr SMÝKAL^2 , Ondřej DOSTÁL^3 , Michaela JARKOVSKÁ^3

and Simona VALOVÁ^4

1 Miroslav, Czech Republic; 2 Faculty of Science, Palacký University Olomouc,

Olomouc, Czech Republic; 3 Mendel Museum and 4 Faculty of Science, Masaryk University,

Brno, Czech Republic

Abstract Schwarzbach E., Smýkal P., Dostál O., Jarkovská M., Valová S. (2014): Gregor J. Mendel – genetics found- ing father. Czech. J. Genet. Plant Breed., 50 : 43–51. Mendel’s impact on science is overwhelming. Although based on the number of scientific papers he published he might be considered a meteorologist, his most significant contribution is his study of plant hybrids. This single work puts Mendel on a par with Darwin’s evolutionary theory and establishes him firmly in the frame of today’s biology. The aim of this article is to introduce the personality of Gregor Johann Mendel, focussing not just on his scientific work, but also on his background and what or who influenced him. To understand Mendel’s use of quantification and mathematical analysis of obtained results, representing a radical departure from methods of his predecessors, it is important to know something about their arguments, beliefs, and practices. He designed his experiments to answer a long standing question of hybridization, not inheritance as we perceive it today, since the science of genetics was born considerably later. He studied many genera of plants, but his famous research was on garden peas. To choose a single species for his crosses was fundamental to his success, but also fuelled most of criticism at the time he presented his results. The reason for his success was partly due to being a hybrid himself: of a biological scientist, a physical scientist and a mathematician. Mendel’s other fields of interest such as meteorology and bee keeping are also introduced in this article. Keywords : heredity; hybridization; manuscript; Mendel; Pisum Gregor Johann Mendel has left an indelible mark on the history of science. His work together with Darwin’s evolutionary theory established the theo- retical basis of today’s biology. Many books have been written about his life, and his discoveries are recorded in almost every biology textbook. The first Mendel biography by Hugo Iltis, 1924, “Gregor Johann Mendel. Leben, Werk und Wirkung” (Iltis 1924), later translated to English (Iltis et al. 1932), is the basic source of information about Mendel, even today. Iltis collected historical documents connected to Mendel and used them as source for his book. The number of these historical documents is limited, but it is not true, that, as often wrongly argued, his personal belongings were burnt after his death. Any- way, the discovery of new information about Gregor Mendel is very rare and other authors can only refer to, supplement or newly interpret what Hugo Iltis documented. The latest book about Mendel, “Soli- tude of a Humble Genius – Gregor Johann Mendel: Volume 1” appeared in 2013 (Klein et al. 2013) and took 10 years of preparation. Before commenting Mendel’s work let’s look at some aspects of his life. Mendel was born, according to the birth record, on 20 th^ of July 1822 at the small village Heinzendorf bei Odrau (then in the Silesian part of Moravia within the Austrian empire, now Hynčice u Vražného in northern Moravia in the Czech Republic) and was baptized Johann the same day. However, according to his nephew, Mendel celebrated his birthday the 22 th^ of July. Contemporary speculations about his nationality (German, Austrian, Silesian, Moravian, Czech) overlook the fact that nationality in its present day sense was barely important in his time. Mendel

Czech J. Genet. Plant Breed., 50, 2014 (2): 43–51 Review

was simply a German speaking inhabitant of the Austrian empire, native to Moravia. Mendel was involved in tending the farm and field work from early childhood. Mendel went eas- ily through various levels of education thanks to his bright mind and ease of learning. He went to the primary school at his native village and later to the Piaristic school at Lipník nad Bečvou. He then attended the Grammar School at Opava, followed by studies at the Philosophical Institute (today Sts Cyril and Methodius Faculty of Theology of the Palacký University) at Olomouc from 1840 to 1843. He struggled with the costs of his education, but was offered to join the St. Augustine order, famous for its support of education and science, at the Mora- vian capital Brno. He did not hesitate and entered the order in 1843 (Figure 1). He passed a number of exams during the first years in the monastery, that were not much related to his preparation for priest- hood, such as in fruit-growing and horticulture. Mendel became a respected substitute teacher at the Grammar School at Znojmo. His efforts to become a legitimate professor of biology and physics led him to take a teacher’s qualification exam in 1850. Unfortunately, he did not succeed, but was recom- mended to study at the University. At the University of Vienna (1851 to 1853), Mendel enrolled in courses with the famous physicist Christian Doppler and the renowned mathematician Andreas von Ettingshausen. Apart from acquiring knowledge in mathematics and physics, Mendel also received education in methods of performing physical experiments, which he used in the careful planning and design of his Pisum experi- ments. Traditional experimentation with hybrids was based on compilation and cataloguing information, followed by drawing conclusions from observations. The radically new approach used by Mendel was the Newtonian, where first a hypothesis is formulated and experiments are then carefully designed to prove or disprove it. Orel (1984) suggests that Mendel might have learned also from a mathematical textbook of Doppler ( 1844 ) with a chapter, that translates “com- binatorial theory and basic principles of probability calculation”. Orel also argues that Mendel might have Figure 1. The Old Brno Augustinians; arrow points to Mendel

Czech J. Genet. Plant Breed., 50, 2014 (2): 43–51 Review

being in his skills a hybrid himself: partly biological scientist, physical scientist, and mathematician. Once his observations were quantified and the relation- ship between the characters described in quality and quantity, Mendel turned to combinatorics and prob- ability to provide arguments supporting the claims made from inductive reasoning, that the characters he is examining remain fixed over generations and are randomly combined in the progeny, following the well known mathematical rules of combinatorics. He used deductive principles of mathematics to present this relationship as a law of nature. To describe biological phenomena by a mathematical model, such as the famous (A + 2Aa + a), was absolutely new in science, but became the basic principle of modern scientific research in any natural science. Such an innovative approach to science sounded strange and unfamiliar to Mendel’s hybridist audience (Wynn 2007) and hard to accept. Although the Society members found Mendel’s results controversial at best, forgettable at worst, his complete lecture was published in the “Verhandlungen des Naturforschenden Vereins in Brünn” (Proceedings of the Natural Science Society at Brünn) in1866 and sent to dozens of institutions across Europe. Of this group of influential and sci- entifically inclined biological researchers, Carl von Nägeli was the only one known to have fully read, considered, and responded to Mendel’s work. The cor- respondence between the two suggests that Mendel’s expressed interest in the Hieracium experiments was an important factor in Nägeli’s motivation to write back. In his response to Mendel’s article and initial letter, the only existing communication of Nägeli’s to Mendel, Nägeli writes at length about Hieracium and asks for Mendel’s help in doing some breeding experiments. Nägeli argued that Mendel cannot as- sume that his belief in the inalterability of traits is good in all cases, he asked to test it on more species. Mendel continued with experiments on other plants, but a significant change happened in 1868, when he became abbot and had to manage the Abbey. He nevertheless continued his research on bees, built in 1871 an apiary and made crosses of various bee lineages. He was also known as a meteorologist, recorded sunspots and made the first ever scientific description of a tornado (Mendel 1871), that swept through Brno in October 1870 and caused consider- able damage. Mendel held also surprising positions, Figure 3. Mendel’s notes

Review Czech J. Genet. Plant Breed., 50, 2014 (2): 43–

such as being director of the Moravian Mortgage Bank from the 1870’s. He died from a kidney infec- tion on 6th^ of January 1884 after a short illness. He was a respected personality in his town and the famous Czech composer Leoš Janáček played the organ at his funeral. Let us now consider two contrasting questions connected with Mendel’s “Experiments with Plant Hybrids“: (a) why were Mendel’s findings so boldly ignored by his contemporaries? and (b) why were Mendel’s findings so compelling to 20th century biologists? Darwin’s evolution theory held that species varied over time, what was also a common opinion among breeders. In an apparent contradiction to it, Mendel believed that the hereditary elements of a species remained constant. Wynn (2007) argued that at least in part, Mendel’s use of mathematical principles was rejected by his contemporaries because of the general opinion, that inherited characters are not stable and, therefore, their transfer to subsequent generations cannot be described by discrete mathematical meth- ods such as probability and combinatorics. Although several different theories have been ad- vanced among historians (Iltis et al. 1932; Orel 1984; Henig 2000), most historians held that Mendel supported the idea that populations of organisms varied over time (Iltis et al. 1932; Henig 2000). Despite evidence suggesting that Mendel’s work sup- ported the Darwinian concept of transmutation of species, closer examination of Mendel’s own words suggests otherwise, that he was more interested in proving that characters did not change over time, as was shown by Orel (2003). Mendel divided his scientific paper, based on experiments conducted from 1850 to 1864, into several parts. The largest section deals with experiments with Pisum, another part deals with other genera such as Phaseolus and the last section contains his concluding remarks. Mendel chose the genus Pisum deliberately, since it fulfilled his three basic requirements for his experi- mental plants (simplified): constancy of characters over generations (true breeding), protection from foreign pollen during flowering and undisturbed fertility of hybrids and offspring. Mendel tested 34 pea varieties during two years and selected 22 for further examination. He noticed also the problems with separation of species or subspecies, but con- sidered this irrelevant for the experiments. He care- fully chose characters, that were easily observable and clearly distinguished the tested varieties, such as flower, seed and pod characters. Mendel grew plants in garden beds and a small proportion in pots. Control plants of each experiment were kept in a greenhouse. Mendel accurately described the individual experiments and the distribution of par- ticular characters in each generation. He examined first plants differing in one and then in two or more characters. Mendel certainly made more experiments than were published and chose the most representative experiments for publication. Mendel lectured about peas already before his experimental work. He stud- ied a total of 15 genera of plants and obtained seeds from colleagues or ordered them. One such order is on display at the Mendel Museum at Brno (Figure 2). Mendel exchanged a series of letters with the recog- nised Swiss professor Carl Wilhelm von Nägeli, who became a critical judge of his work. Mendel wrote Nägeli about his appointment as abbot and about hopes to find eventually more time for his experiments. This, unfortunately, never happened. Mendel finished his experiments around 1870. Perhaps for lack of time Figure 4. Mendel’s notes about research on Geum

Review Czech J. Genet. Plant Breed., 50, 2014 (2): 43–

Figure 5. Mendel’s manuscript; the middle part of his work on peas (continuation)

Czech J. Genet. Plant Breed., 50, 2014 (2): 43–51 Review

In symbolic writing, using “A“ and “a“ for the domi- nant and the recessive allele, respectively, there are four possible combinations: AA, Aa, aA and aa. The first three combinations look the same (for example purple) due to the presence of the dominant allele, while the last combination looks different (for ex- ample white). The progeny of AA consists entirely of AA indi- viduals and the progeny of aa entirely of aa individu- als. The progeny of Aa or aA consists of randomly distributed individuals of all four categories. If we join the categories Aa and aA , the frequency of the categories in the progeny conforms to the famous formula 1AA:2Aa:1aa. This was later declared as the Law of Segregation. During the formation of gametes (eggs and pollen) each gamete receives randomly one of the two alleles of each gene. During fertilisation (fusion of the egg with the pollen) the number two of alleles is again restored and the alleles in the hybrid results from the combination of two random gametes. This was later declared as the Law of Independent Assortment. Mendel himself did not formulate these laws. As was written in an obituary of G. Mendel – Di- rect, epochal significance, however, he had through his research about plant hybrids. What he did and created, remains an immortal monument! R e f e r e n c e s Bateson W. (1913): Mendel’s Principles of Heredity. Cam- bridge University Press, Cambridge. Doppler C. ( 1844 ): Arithmetik und Algebra: Mit beson- derer Rücksicht auf die Bedürfnisse des praktischen Leb- ens und der technischen Wissenschaften. Borrosch & Andrée, Prag. Henig R.M. ( 2000 ). The Monk in the Garden. Houghton Mifflin, Boston. Iltis H. (1924): Gregor Johann Mendel: Leben, Werk und Wirkung. Prague: Herausgegeben mit Unterstuetzung des Ministeriums für Schulwesen und Volkskultur in Prag. Julius Springer, Berlin. Iltis H., Eden P., Cedar P. ( 1932 ): Life of Mendel. G. Allen & Unwin, London. Klein J., Klein N., Klein P. (2013): Solitude of a Humble Genius – Gregor Johann Mendel: Volume 1. Springer, New York. Figure 5. Mendel’s manuscript; the middle part of his work on peas (continuation)

Gregor J, Mendel teorías, Guías, Proyectos, Investigaciones de Genética

Documentos relacionados

Vista previa parcial del texto

¡Descarga Gregor J, Mendel teorías y más Guías, Proyectos, Investigaciones en PDF de Genética solo en Docsity!

Review Czech J. Genet. Plant Breed., 50, 2014 (2): 43–

Gregor J. Mendel – Genetics Founding Father

Erik SCHWARZBACH 1 , Petr SMÝKAL^2 , Ondřej DOSTÁL^3 , Michaela JARKOVSKÁ^3

and Simona VALOVÁ^4

1 Miroslav, Czech Republic; 2 Faculty of Science, Palacký University Olomouc,

Olomouc, Czech Republic; 3 Mendel Museum and 4 Faculty of Science, Masaryk University,

Brno, Czech Republic

Czech J. Genet. Plant Breed., 50, 2014 (2): 43–51 Review

Czech J. Genet. Plant Breed., 50, 2014 (2): 43–51 Review

Review Czech J. Genet. Plant Breed., 50, 2014 (2): 43–

Review Czech J. Genet. Plant Breed., 50, 2014 (2): 43–

Czech J. Genet. Plant Breed., 50, 2014 (2): 43–51 Review