Gregor Johann Mendel: Father of Genetics

Scientists Decode Black Dahlias:Vienna, Nov 25, 2012: Scientists have now decoded why some dahlias are black, a rarity, after analyzing as to why the plant displays varying hues, from white to yellow to red to purple.

Dahlia variabilis hort. is a popular garden flower. Continuous dahlia breeding worldwide has led to a huge number of cultivars many of them showing red hues, but black hues of dahlia flowers occur rarely. Credit: Dr. Heidi Halbwirth

To examine the biochemical basis for the distinctive dark coloring of the black dahlia, the research team from the Vienna University of Technology in Austria used pigment, enzyme and gene expression analyses. They determined that the majority of black cultivars have very low concentrations of flavones, as confirmed by low FNS II expression. Since flavones compete with anthocyanin biosynthesis for common intermediates, the lack of flavones favors the accumulation of huge amounts of anthocyanins that are found in black dahlias. The flavonol contents of black dahlias increased slightly parallel to the decrease of flavones. (Citation: Jana Thill, Silvija Miosic, Romel Ahmed, Karin Schlangen, Gerlinde Muster, Karl Stich and Heidi Halbwirth, ''Le Rouge et le Noir': A decline in flavone formation correlates with the rare color of black dahlia (Dahlia variabilis hort.) flowers', BMC Plant Biology 2012, 12:225) 

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Every research paper in Genetics 

reminds us a genius of all time

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The monk in the garden

Gregor Johann Mendel

The Father of Genetics

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AKA Gregor Johann Mendel

Born: 22-Jul-1822Birthplace: Hynice, CzechiaDied: 6-Jan-1884Location of death: Brno, CzechiaCause of death: unspecifiedRemains: Buried, Central Cemetery, Brno, Czechia

Gender: MaleReligion: Roman CatholicRace or Ethnicity: WhiteOccupation: Scientist, Botanist, Religion

Nationality: CzechiaExecutive summary: Discovered the laws of inheritance

Father: Anton (farmer)Mother: RosineSister: VeronicaSister: Theresia

    High School: Troppau Gymnasium, Opava, Czechia (1840)
    University: Olmutz Philosophical Institute (1840-43)
    Theological: Brünn Theological College, Brno, Czechia (1847)
    Teacher: Znojmo Gymnasium, Znojmo, Czechia (1849-51)
    Teacher: Mathematics and Biology, University of Vienna (1851-54)
    Administrator: Abbot and Prelate, St Thomas's Abbey, Brno, Czechia (1854-68)

    Ordained by the Roman Catholic Church 6-Aug-1847
    Asteroid Namesake 3313 Mendel
    Lunar Crater Mendel (48.8° S, 109.4° W, 138 km. diameter)
    Martian Crater Mendel (58.8° S, 161° E, 79 km. diameter)

The Lost and Found Genius of Gregor Mendel: Most people know that Gregor Mendel, the Moravian monk who patiently grew his peas in a monastery garden, shaped our understanding of inheritance. But people might not know that Mendel's work was ignored in his own lifetime, even though it contained answers to the most pressing questions raised by Charles Darwin's revolutionary book, ON ORIGIN OF THE SPECIES, published only a few years earlier. Mendel's single chance of recognition failed utterly, and he died a lonely and disappointed man (Before his death in 1884 he wrote, "I am convinced that it will not be long before the whole world acknowledges the results of my work,"). Thirty-five years later, his work was rescued from obscurity in a single season, the spring of 1900, when three scientists from three different countries nearly simultaneously dusted off Mendel's groundbreaking paper and finally recognized its profound significance. The perplexing silence that greeted Mendel's discovery and his ultimate canonization as the father of genetics make up a tale of intrigue, jealousy, and a healthy dose of bad timing. 

In 1857, Austrian monk Gregor Mendel decided to breed pea plants in the large monastery garden of Brunn. He loved botany (studying plants) and he had very much wanted to become a high school teacher. Unfortunately, he had failed the teaching exam three times, so he had to be content with living as a monk. It took him eight years and 30,000 pea plants to discover these natural laws of heredity (now known as the Mendelian Laws). Afterwards, Mendel wished to publish his findings, but feared that no one would listen to him because he was only a monk and not even qualified to teach high school! Nevertheless, he sent his reports to the most famous botanist in Europe, Karl Wilhelm von Nageli of Switzerland, hoping to gain his sponsorship (support of his work). von Nageli ignored Mendel's work, though, and sent it back to him. Mendel was able to get his paper published in a scientific journal several years later, but - just as he had feared - no one acknowledged it because he was an unsponsored amateur. Saddened, he gave up botany and devoted his days to monastic life. Mendel died in 1884. It was nearly forty years later when his writings and research were rediscovered and found to be true.

On New Year's Eve, 1866, Gregor Mendel wrote to the prominent Swiss botanist Carl Nägeli to tell him about his now classic experiments with Pisum peas. In the margins of the letter, Nägeli scribbled a note: "only empirical and not rational."

MENDEL, Gregor (1822-84). 

Mendel was born on July 22, 1822 in Heizendorf, Austria, (now known as Hyncice in Czechoslovakia). He was born Johann Mendel into a poor farming family. At that time it was difficult for poor families to obtain a good education and the young Mendel saw the only way to escape a life of poverty was to enter the monastery at Brunn in Moravis, (now Brno in Czechoslovakia). Here he was given the name Gregor. This monastery was the Augustinian Order of St Thomas, a teaching order with a reputation as a centre of learning and scientific enquiry.

He took the name Gregor when he entered the monastery in Brunn, Moravia (now Brno, Czech Republic) in 1843. He studied for two years at the Philosophical Institute in Olmutz (now Olomouc, Czech Republic), before going to Brunn. He became a priest in 1847. For most of the next 20 years he taught at a nearby high school, except for two years of study at the University of Vienna (1851-53). In 1868 Mendel was elected abbot of the monastery.

To enable him to further his education, the abbot arranged for Mendel to attend the University of Vienna to get a teaching diploma. However, Mendel did not perform well. He was nervous and the University did not consider him a clever student. Mendel's examiner failed him with the comments, " he lacks insight and the requisite clarity of knowledge". This must have been devastating to the young Mendel. who in 1853 had to return to the monastery as a failure.

Mendel's famous garden-pea experiments began in 1856 in the monastery garden. He proposed that the existence of characteristics such as blossom color is due to the occurrence of paired elementary units of heredity, now known as genes. Mendel presented his work to the local Natural Science Society in 1865 in a paper entitled "Experiments with Plant Hybrids." (Gregor Mendel 1865.Versuche uber Pflanzen-Hybriden. Verh. Naturfosch. Ver. Brunn, Vol 4:3-47.) Administrative duties after 1868 kept him too busy for further research. He lived out his life in relative obscurity, dying on Jan. 6, 1884. In 1900, independent research by other scientists confirmed Mendel's results.

Mendel's garden plot at the Augustine monastery in Brno, Czech Republic.

He published his results in the Journal of the Brno Natural History Society in 1866, writing:

"It is now clear that the hybrids form seeds having one or other of two differentiating characters, and of these one half develop again the hybrid form, while the other half yield plants which remain constant and receive the dominant or the recessive characters in equal numbers."

Mendel's field notes

While Mendel's research was with plants, the basic underlying principles of heredity that he discovered also apply to people and other animals because the mechanisms of heredity are essentially the same for all complex life forms.

Through the selective cross-breeding of common pea plants (Pisum sativum) over many generations, Mendel discovered that certain traits show up in offspring without any blending of parent characteristics.  For instance, the pea flowers are either purple or white--intermediate colors do not appear in the offspring of cross-pollinated pea plants.  Mendel observed seven traits that are easily recognized and apparently only occur in one of two forms:

1.	flower color is purple or white	5.	seed color is yellow or green
2.	flower position is axil or terminal	6.	pod shape is inflated or constricted
3.	stem length is long or short	7.	pod color is yellow or green
4.	seed shape is round or wrinkled

Experiments on plant hybridization:

In cross-pollinating plants that either produce yellow or green pea seeds exclusively, Mendel found that the first offspring generation (f1) always has yellow seeds.   However, the following generation (f2) consistently has a 3:1 ratio of yellow to green

 

This 3:1 ratio occurs in later generations as well.   Mendel realized that this was the key to understanding the basic mechanisms of inheritance.

He came to three important conclusions from these experimental results:

1.	that the inheritance of each trait is determined by "units" or "factors" that are passed on to descendents unchanged      (these units are now called genes)
2.	that an individual inherits one such unit from each parent for each trait
3.	that a trait may not show up in an individual but can still be passed on to the next generation.

It is important to realize that, in this experiment, the starting parent plants were homozygous for pea seed color.  That is to say, they each had two identical forms (or alleles) of the gene for this trait--2 yellows or 2 greens.  The plants in the f1 generation were all heterozygous.   In other words, they each had inherited two different alleles--one from each parent plant.  It becomes clearer when we look at the actual genetic makeup, or genotype , of the pea plants instead of only the phenotype, or observable physical characteristics.

Note that each of the f1 generation plants (shown above) inherited a Y allele from one parent and a G allele from the other.  When the f1 plants breed, each has an equal chance of passing on either Y or G alleles to each offspring.

With all of the seven pea plant traits that Mendel examined, one form appeared dominant over the other, which is to say it masked the presence of the other allele.  For example, when the genotype for pea seed color is YG (heterozygous), the phenotype is yellow.  However, the dominant yellow allele does not alter the recessive green one in any way.   Both alleles can be passed on to the next generation unchanged.

Mendel's observations from these experiments can be summarized in two principles:

1.	the principle of segregation
2.	the principle of independent assortment

According to the principle of segregation, for any particular trait, the pair of alleles of each parent separate and only one allele passes from each parent on to an offspring.  Which allele in a parent's pair of alleles is inherited is a matter of chance.  We now know that this segregation of alleles occurs during the process of sex cell formation (i.e.meiosis).

Segregation of alleles in the production of sex cells

According to the principle of independent assortment, different pairs of alleles are passed to offspring independently of each other.  The result is that new combinations of genes present in neither parent are possible.  For example, a pea plant's inheritance of the ability to produce purple flowers instead of white ones does not make it more likely that it will also inherit the ability to produce yellow pea seeds in contrast to green ones.  Likewise, the principle of independent assortment explains why the human inheritance of a particular eye color does not increase or decrease the likelihood of having 6 fingers on each hand.  Today, we know this is due to the fact that the genes for independently assorted traits are located on different chromosomes 

These two principles of inheritance, along with the understanding of unit inheritance and dominance, were the beginnings of our modern science of genetics.

Gregor Mendel's genius spelt out in a pea-flavoured Google doodle. Born into poverty on a farm in Austria, Gregor Mendel and his peas went on to sow the seeds of modern genetics

*Note: all pictures thankfully shared from various sources.