Mendel's work with pea plants in the mid-19th century laid the foundations of genetics by demonstrating that traits are passed from parents to offspring through discrete units of inheritance. During the early 20th century, scientists such as Morgan and Sutton connected Mendel's theories to chromosomes and the cellular basis of inheritance. The emergence of molecular genetics in the mid-20th century revealed that DNA carries the genetic information that is passed from cell to cell and between generations.

2. OVERVIEW
• Origin of Genetics
• Classical Genetics(1915-1950)
• Institutionalization of Genetics
• Emergence of Molecular Genetics
• Classical to Molecular concepts of Genes
• Conclusion

3. ORIGINS OF
GENETICS

4. GREGOR MENDEL(1822-1884)
• USE of 7 Charachters
of Garden PEA

5. Characters
• Flower color
• Flower position
• Seed color
• Seed shape
• Pod shape
• Pod color
• Stem length

6. Mendel’s Laws of Inheritance
• Law of Independent Assortment
 In monohybrid cross the alleles separate
independently from each other.
• Law of Segregation
 Two alleles coding for the same trait separate
during gamete formation.

8. LAMARCKISM
• The hypothesis that an organism can pass on
characteristics that it has acquired during its
lifetime to its offspring. It is also known as the
heritability of acquired characteristics or soft
inheritance.

10. Charles Darwin (1809-1882)

11. • Theory of Natural Selection
 Only the organisms best adapted to their environment tend to
survive and transmit their genetic characters in increasing
numbers to succeeding generations while those less adapted
tend to be eliminated.(Survival of the fittest)
• Theory of Evolution
 All species of organisms arise and develop through the natural
selection of small, inherited variations that increase the
individual's ability to compete, survive, and reproduce.OR it
can be stated as all species have a common ancestor.

13. Walter Sutton(1877-1916)
• Boveri-Sutton Chromosome Theory
 Mendelian laws of inheritance could be applied to
chromosomes at the cellular level of living
organisms.

14. Hugo De Vries , Carl Correns , Eric Von
Tschermac

15. • Three scientists who rediscovered Mendel's
laws in 1900.
• They were all working independently on
different plant hybrids, and came to the same
conclusions about inheritance as Mendel.

16. CLASSICAL
GENETICS

17. AUGUST WEISMANN(1834-1914)
• Suggested that the remarkable behavior of
chromosomes during cell division was
important for the knowledge of variation and
heredity.

18. GERM PLASM THEORY
• heritable information is transmitted only by
germ cells in the gonads (ovaries and testes),
not by somatic cells.
• The idea that information cannot pass from
somatic cells to the germ line is called the
Weismann barrier.
• The theory to some extent anticipated the
development of modern genetics.

19. ROSALIND FRANKLIN(1920-1958)
• 1st study the chromosomes.
• The brilliant chemist whose x-ray diffraction
studies provided crucial clues to the structure
of DNA.

20. • X-ray diffraction "photo 51" of DNA made by
Rosalind Franklin provided clues for Watson
and Crick to discover the structure of DNA.

21. FRIEDRICH MIESCHER(1844-1895)
• Discovered a new type of
weak acid, abundant in the
nuclei of the white blood
cell; Miescher's weak acid
turned out to be the
chemical substance we now
call deoxyribonucleic acid or
DNA.

22. WATSON-CARRICK model of DNA
• Watson and Carrick proposed the model of
DNA in 1953.
• They were awarded noble prize for their work
in physiology or medicine in 1962.

24. Institutionalization
Of Genetics

25. • Signs of the institutionalization of genetics in the
early 20th century include: the creation of chairs
explicitly devoted to genetics, the publication of
textbooks, innumerable courses of genetics all
over the world; the creation of specialized
journals.
• Development of the new science: animal
breeding, plant breeding and horticulture were
powerful incentives, and provided resources for
genetic research in all advanced countries.

26. SPECIALIZATION in GENETICS
• Institutionalization also meant specialization.
In the mid-1930s, genetics was conventionally
subdivided into four major sub-disciplines:
 Transmission Genetics
 Molecular Genetics
 Population Genetics
 Quantitative Genetics

28. EMERGENCE of
MOLECULAR
GENETICS

29. Genetic control of biochemical
reactions in Neurospora
• The connection of genetics with biochemistry was
showed by Beadle and Tatum’s 1941 paper ‘Genetic
control of biochemical reactions in Neurospora’, which
offered the first proof that a specific gene controls a
biochemical reaction . they proposed that “genes
control or regulate specific reactions in the system
either by acting directly as enzymes or by determining
the specificities of enzymes.”
• In the following years, still working on the mold
Neurospora crassa, they showed that a single gene
controls each step in a metabolic pathway .

30. EXPERIMENTS by Avery, MacLeod,
and McCarty
• This experiment showed that purified DNA
extracted from a dead virulent pneumococcus
was able to ‘transform’ a non-virulent strain of
pneumococcus (a bacterium able to cause
acute pneumonia) into a virulent strain.

31. CLASSICAL to
MOLECULAR
WORK OF GENE

32. TIMELINE
• 1952 - Alfred Hershey & Martha Chase
demonstrate that DNA contains genetic material.
• 1958 -Isolation of the first enzyme (DNA
polymerase I) by A. Kornberg.
• 1959 - Discovery of RNA polymerase. 1960 -
Discovery of messenger RNA. 1961 - The triplet
nature of the genetic code is discovered.
• 1966 - Establishment of complete genetic code.
1967 - Isolation of the enzyme DNA ligase. 1970 -
Isolation of the first restriction enzyme.

33. • 1977 - DNA sequencing becomes possible.
• 1981 - Catalytic activity of RNA is discovered.
Transgenic mice and flies are obtained by introducing
new DNA into the germ line.
• 1983 - First version of "GenBank" created for storage of
DNA sequences.
• 1989 - Polymerase Chain Reaction (PCR) technique first
used. 1995 - First BACTERIAL genomes completely
sequenced.
• 1997 - Dolly the Sheep cloned.
• E.coli genome sequenced.
• 2004 - The Homo sapiens genome (3000 MB) is
sequenced.
• 2009 – Full Genome sequencing.

34. CONCLUSION
The findings of molecular biology have deeply altered
the theoretical framework of genetics. Some authors
claim that genetics has been replaced by the concepts
and methods of molecular biology, the object of
which incidentally is not only to study inheritance. In
the history of science, theoretical frameworks do not
totally replace one another, but partially overlap. In
biology, genetics remains indispensable at certain
level of description, especially when heredity rather
than physiological functioning is the key problem .
Therefore, rather than saying that the concept of
gene and therefore genetics is dead , we prefer to
conclude that its relevance is a matter of scientific
context.