Tuesday, 20 November 2012

Father of Genetics - Childhood Days

 

Gregor Mendel Austrian botanist, teacher, and Augustinian prelate,
the first to lay the mathematical foundation of the science of genetics, in what came to be called Mendelism

Gregor Mendel (July 20, 1822 - January 6, 1884) his childhood name was Johann, which he changed to Gregor when he became a Priest.
Johann was born as one of the three children to his peasant parents Anton and Rosine Mendel on July 20 1822 (baptized on July 22) on his family’s farm, in what was then Heinzendorf, a province of the Austrian Empire, now the Czech Republic. The place of birth village called Heinzendorf, is now called Hyncice. The area borders where Germany, Poland, and the Czech Republic come together.

Mendel's childhood home, the one with the grey top

CHILDHOOD is the most impressionable of all the stations in one's life. It molds a person's character, spins dreams, and leaves everlasting memories. Mendel's father owned a 45-acre farm; however, the family lived a frugal life with little money for "extras." Johann worked with his father a lot in the family orchard, which stimulated his interest in the things of nature. He learned to love growing plants and gardening, a love that he brought to his scientific research when he grew up.
Another thing that influenced his later life was his puzzlement about why he had a mixture of his parents' traits, but his sisters did not. Johann had the short stocky build of his father and the cheerfulness and language skills of his mother.  His elder sister Veronica was more like the father, both in appearance and disposition, while a younger sister Theresia was more like the mother.
Johann spent his early youth in that rural setting, until age 11. The garden, the fields, and the brook were Johann's playfields. The brook winding along the road, in particular, must have been his favorite retreat. Here there were fish and crayfish to catch, small mammals to observe, bird nests to spy out in the bushes, and a great variety of plants to enjoy and to wonder what their names might be. Only years later would he learn that the yellow, star-shaped flowers are the Gagea lutea or that the pink racemes of spurred flowers are Corydalis cava. Johann's playfields were, however, also places of hard work; at that time, every pair of hands counted on a farm, even those of a child. The list of his duties and responsibilities around the house that undoubtedly had always been long, grew, and became diversified with age: sweep the yard; take the ducks down to the brook and keep an eye on them; feed the rabbits and the hens; chop the wood; fetch water from the well for the kitchen and the stables; clean the stables and the barn; take the goat to the pasture, rake over the hay on the meadow; take care of Theresia, the younger sister; hoe the vegetable garden; in the field … the list was inexhaustible. Every time he thought he had five minutes to pursue his own interests, he would hear either his mother or his father calling him, which invariably meant that the next task awaited him. Only on Sunday afternoons did he find himself relatively free. Sunday mornings were reserved for church attendance.
Small Chapel in Hyncice
Johann, Veronika, and their father always dressed up to attend High Mass at Vrážné, a half-hour walk from their house. Although Hynčice had a small chapel, regular services were held only in the spacious baroque church at Vrážné. There  Johann would listen to sermons delivered by the vicar, his future teacher and the man who would soon determine his fate, Father Johann Schreiber. The vicarage at Vrážné also housed the registers in which Johann Mendel's birth was recorded, perhaps erroneously, and the cemetery around the church was the site where his ancestors lay and where one day his parents, and later also his kin, would find their final rest.
When Johann reached school age, his leisure time was reduced even further. The day's workload did not become any lighter—it was simply compressed into a shorter time interval. Often his path after school led him directly to the field where he would toil until nightfall when he finally arrived home and had finished his daily chores and done his homework, it was already bedtime.
In 1831 Johann’s parents sent him to Elementary school in Hynice, but hoped, as their only son, that he would one day take over the farm. Farmers were compelled to labor a few days every week for local landowners, getting only four days a week to farm their own land.
Johann learned the "3 R’s - reading, writing and arithmetic," plus the essentials of fruit growing and bee keeping. To reach the Hynčice public school, he had to cross the brook and walk a hundred meters or so up the hill. It was a single-class school, which meant that pupils of different ages and at different stages in their education, often numbering up to 80 heads, were all taught in one room. The teacher of such a large, heterogeneous group had to have the skills of an orchestra conductor to keep the various other groups busy while he worked with one of them. The village teacher, Thomas Makitta, and the vicar, Johann Schreiber, apparently possessed this skill. Schreiber taught religion and natural history, Makitta the rest. To include natural history in the school's curriculum was highly unusual, and the disapproving authorities put an end to this Unfug (nonsense), as one of the officials called it.
Both Makitta and Schreiber were quick to realize that Johann had special ability, being what we would call today as "gifted and talented." Johann had heard about a more exciting school at Leipnik, a town about 13 miles away.  It was much like today's Middle Schools.  Two boys in Heinzendorf were going to this school and on their vacations they impressed Johann and the other local children with all the new things they were learning.

Both Mendel's teachers argued with his parents that his talent would be wasted if they did not allow him to study, regardless of the sacrifice it involved. Anton Mendel resisted the idea initially, for he was expecting Johann to take over the farm one day, but eventually he gave in. In the autumn of 1833 Mendel moved to the Piarist School in Lipnik.

Ponds near Pohoř

And so, after a one-year trial period at the Piarist school in Lipník in the late summer of 1834, the 12-year-old Johann loaded his meager belongings, consisting of a few articles of clothing and large food provisions, onto a horse-drawn cart and set out on the day-long journey to Opava. The route took him past the ponds near Pohoř, which he probably knew from his wanderings, past the picturesque castle in Fulnek, through the dense, dark forests of Vítkovská vrchovina, the scene of many robber and highwayman stories, past the Hradec castle, where a few years earlier Ludwig van Beethoven had refused to play the piano for the officers of the occupying French army, and on to the Silesian capital. The sight of the imposing building, the Gymnasium (grammar school) in Opava (in German called Troppau), that now bears his name, must have both impressed and terrified him. Childhood in his field of dreams was over. Six long years of hardship and deprivation lay before him …


Wednesday, 3 October 2012

Evolution of Genetics - Theory of Natural Selection

Charles Darwin


Darwin, aged 45 in 1854,
 by then working towards publication of On the Origin of Species

Charles Robert Darwin, (12 February 1809 – 19 April 1882) was an English naturalist. In 1859, Charles Darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. He defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".

The concept was simple but powerful: individuals best adapted to their environments are more likely to survive and reproduce. As long as there is some variation between them, there will be an inevitable selection of individuals with the most advantageous variations. If the variations are inherited, then differential reproductive success will lead to a progressive evolution of particular populations of a species, and populations that evolve to be sufficiently different eventually become different species

Although Darwin was very successful at convincing his contemporaries about the fact that evolution had occurred, he was much less successful at convincing his colleagues that his mechanism of Natural Selection was the major mechanism of evolutionary change.  This was mainly because there was no satisfactory explanation for inheritance, or for how variation originated.

Darwin himself was plagued by his inability to understand inheritance, and was dissatisfied by his own theory of inheritance, pangenesis and blending inheritance, because blending suggested that variation should be halved each generation and would rapidly be lost.

Darwin's lack of a model of the mechanism of inheritance left him unable to interpret his own data that showed Mendelian ratios, even though he shared with Mendel a more mathematical and probabilistic outlook than most biologists of his time.

"The laws governing inheritence are quite unknown; no one can say why a peculiarity in different individuals of the same species…is sometimes inherited and sometimes not; why the child often reverts in certain characters to its grandfather or grandmother or other more remote ancestor." Charles Darwin, The Origin of Species, 1859

Darwin's own “pangenesis” model provided a mechanism for generating ample variability on which selection could act. It involved, however, the inheritance of characters acquired during an organism's life, which Darwin himself knew could not explain some evolutionary situations. [Once the particulate basis of genetics was understood, it was seen to allow variation to be passed intact to new generations, and evolution could then be understood as a process of changes in the frequencies of stable variants.]

Evolutionary genetics subsequently developed as a central part of biology. Darwinian principles now play a greater role in biology than ever before, which we illustrate with some examples of studies of natural selection that use DNA sequence data and with some recent advances in answering questions first asked by Darwin.

References:


Friday, 28 September 2012

The Human Genome Project



What is the Human Genome Project?

Begun formally in 1990, the U.S. Human Genome Project was a 13-year effort coordinated by the U.S. Department of Energy and the National Institutes of Health. The project originally was planned to last 15 years, but rapid technological advances accelerated the completion date to 2003.

Goals
  • Identify all the approximately 20,000-25,000 genes in human DNA,
  • Determine the sequences of the 3 billion chemical base pairs that make up human DNA,
  • Store this information in databases,
  • Improve tools for data analysis,
  • Transfer related technologies to the private sector, and
  • Address the ethical, legal, and social issues (ELSI) that may arise from the project.

Milestones
  • Anticipated1990: Project initiated as joint effort of U.S. Department of Energy and the National Institutes of Health
  • June 2001: Completion of a working draft of the entire human genome (covers >90% of the genome to a depth of 3-4x redundant sequence)
  • February 2001: Analyses of the working draft are published
  • April 2003: HGP sequencing is completed and Project is declared finished two years ahead of schedule


Anticipated Benefits
  • Improved diagnosis of disease
  • Earlier detection of genetic predispositions to disease
  • Rational drug design
  • Gene therapy and control systems of drugs
  • Personalized, control drugs


To help achieve these goals, researchers also studied the genetic makeup of several nonhuman organisms. These include the common human gut bacterium Escherichia coli, the fruit fly, and the laboratory mouse.

What's a genome? And why is it important?

A genome is all the DNA in an organism, including its genes. Genes carry information for making all the proteins required by all organisms. These proteins determine, among other things, how the organism looks, how well its body metabolizes food or fights infection, and sometimes even how it behaves.

DNA is made up of four similar chemicals (called bases and abbreviated A, T, C, and G) that are repeated millions or billions of times throughout a genome. The human genome, for example, has 3 billion pairs of bases.

The particular order of As, Ts, Cs, and Gs is extremely important. The order underlies all of life's diversity, even dictating whether an organism is human or another species such as yeast, rice, or fruit fly, all of which have their own genomes and are themselves the focus of genome projects. Because all organisms are related through similarities in DNA sequences, insights gained from nonhuman genomes often lead to new knowledge about human biology.

References: