its my university task to make a assignment on the brief history of molecular biology i am sure i done it quite well by linking all the information to molecular

1. SP13-bty-001 Zohaib Hussain Molecular Biology
The Brief History Of Molecular Biology
Introduction:
The first step which leads towards the development of field of biology is the use of microscope.
Scientist searches the features of biology of living things by manipulating it.
The main component of every living thing is a CELL (a basic unit of life) and renowned discove
ry of cell is done by the Robert Hooke
Background of molecular biology:
Before studying history in details we need to know what molecular biology is.
“It is the study of gene structure and function at molecular level”
Molecular biology history is studied in two broad perspectives
 Study of genetics
 Study of biochemistry
Both of the above fields comprised the molecular biology in it (A hybrid discipline).
Early history:
The first concept rise in the mind of people about inheritance is called as blending concept also
called as a blending inheritance.
People of the 17th century and early 18th century believes in a blending concept which is that t
he offspring results after the cross is the mixture of the 2 parents i.e. a blending of each trait of
parents in the offspring
The Greg or Mendel discover his findings about the inheritance after examining the inheritance
in 7 different traits of garden pea ( Pisum sativum ).Mendel proposed the laws of inheritance .
He concludes that each parent contributes a particle or genetic unit to the offspring.
e.g In the cross of yellow pea and green peas: a yellow parent contributes a gamete with a gene f
or yellow seeds and the green parent a gamete with a gene for green seeds therefore all the F1
generation got one allele for yellow seeds and one allele for green seeds . they had not lost allele
for green seed at all , but because yellow is dominant , all the seeds were yellow, however when
these homozygous seed were well fertilized , they produced gametes containing allele for yello
w and green color in equal in numbers and this allow green phenotype to reappear.

2. SP13-bty-001 Zohaib Hussain Molecular Biology
The study of Mendel gives a concept about allele, dominant, recessive, homozygote,
heterozygote, monohybrid and dihybrid.
Mendel didn’t know about gene, chromosomes but his concept leads towards its role in the genet
ics Mendel works is called as a particulate theory or transmission genetics
Rediscovery of Mendel work:
Mendel work is not uniformly accepted it is rejected uniformly because of an old blending
concept and secondly people were unfamiliar of Mendel work too
In the early 19th
century 3 scientist rediscover Mendel work and accepted it because of the follow
ing reasons
 Nature of chromosome revealing is according to Mendel work
 The concept that gamete contain only one allele i.e n number of chromosome
Three botanists - Hugo DeVries, Carl Correns and Erich von Tschermak - independently redisco
vered Mendel's work in the same year, a generation after Mendel published his papers. They help
ed expand awareness of the Mendelian laws of inheritance in the scientific world.
The three Europeans, unknown to each other, were working on different plant hybrids when they
each worked out the laws of inheritance. When they reviewed the literature before publishing th
eir own results, they were startled to find Mendel's old papers spelling out those laws in detail.
Each man announced Mendel's discoveries and his own work as confirmation of them.
The Fruit Fly Scientist work
Morgan wanted to understand heredity and mutation, which is genetic change. At Columbia
University Morgan established the famous "fly room." The Drosophila melanogaster, or fruit fly
, is a good genetic research subject because it can be bred cheaply and reproduces quickly. Morg
an was not the first to use the fruit fly as a subject, but his innovation and success popularized its
use. Simple in design and easy to conduct, his early experiments are classics in genetics.
By painstakingly examining thousands upon thousands of flies with a microscope and a magnifyi
ng glass, Morgan and his colleagues confirmed the chromosomal theory of inheritance: that
genes are located on chromosomes like beads on a string, and that some genes are linked (meani
ng they are on the same chromosome and always inherited together)
The concept of mutant, wild type, sex linkage, autosomes and sex chromosome are
introduced.

3. SP13-bty-001 Zohaib Hussain Molecular Biology
Recombination and genetic mapping:
One of his students, in 1913 Alfred Sturtevant, created the first ever genetic map, a landmark e
vent in genetics, he also discovered the genetic mapping techniques still used.
Morgan concludes that genes are arranged in a linear fashion on the chromosome like beads on a
string. This together with his awareness of recombination led him to proposed that the
farther apart two genes are on the chromosome; the more likely they are to recombine. So
more chances of crossing over in a widely spaced genes.
The other scientist e.g. Barbara, Harriet, curt stern, discover the phenomenon of
recombination in maize drosophila etc
The above studies tell us about the transmission of genes and mapping of gene too but still
scientist didn’t know how gene work and what are they made off.
The milestone in molecular history discovery of DNA
In 1869 Friedrich Miescher discovered DNA he called it “nuclein” and tells that it is composed
of carbon nitrogen phosphorus and hydrogen .It would be years before the role of nucleic acids w
ere recognized. Miescher, himself, believed that proteins were the molecules of heredity.
However, Miescher laid the groundwork for the molecular discoveries that followed.
Rosald avery in 1944 suggested that DNA is a transformation source as indicated in the Griffith
experiment the chemical nature of transforming agent in the mouse strain causing death is DNA
George beadle and E l Tatum prove the relationship between the gene and enzyme revealing
the Garrod work1900 that alkaptonaria is caused due to abnormal buildup of an intermediate
compound in your biochemical pathway which are catalyzed by proteins called enzymes .
a defective gene give rise to a defective enzyme. In other words gene some to be a responsible
for a making one enzyme. This was the one gene / one enzyme hypothesis. Hypothesis leads
to false because most genes contain the information for making one polypeptide.
How genes are replicated. Production of RNA and Proteins?
The 3D structure Of DNA is discovered James Watson and crick 1953 based on the physical
and chemical data that he collected n the laboratories primarily on the X ray diffraction data

4. SP13-bty-001 Zohaib Hussain Molecular Biology
collected by Rosalind Franklin and Maurice Wilkins
In 1958 Mathew Meselson and Franklin stahl proved the DNA replication in bacteria
following semi conservative model .
1956 Francis Crick and George Gamov worked out the "Central Dogma" to explain protein
synthesis from DNA: the DNA sequence codes for amino acid sequences and genetic
information flows in one direction - from DNA to mRNA to protein
Genes expression is the process by which a gene product (an RNA or a polypeptide) is made it’s
a two steps process called transcription and translation are required to make a polypeptide fro
m the instruction in a DNA gene
According to crick each ribosome is responsible for the production of making only one protein
but later on francious Jacob and Sydney Brenner give idea that ribosome’s can make a
unlimited number of different proteins according to instruction in the mRNA that visit the
ribosome’s this idea is proved correct in later stages
Now question arises which parts of gene encodes a amino acid sequence?
Marscall Nirenberg and Gobind khorana working independently with different concepts revea
l the code in the early 1960s they found that 3 bases constitute a code word called a Codon that
stands for one amino acids. Out of the 64 possible 3-base Codons, 61 specify amino acids the ot
her 3 are stop signals
Later advancements in molecular biology:
1. (1970) Howard Temin and David Baltimore independently isolated reverse
transcriptase, an enzyme that can make DNA from RNA
2. (1972) Paul Berg used a restriction enzyme to cut DNA and ligase to past two DNA stran
ds together to form hybrid circular molecule. This was the first recombinant DNA mole
cule
3. (1977)Bacteriophage FX-174 (5368 bp) was the first complete genome (DNA) to be sequ
enced

5. SP13-bty-001 Zohaib Hussain Molecular Biology
4. (1990) Human Genome Project launched: estimated cost of $13 billion (plan 15 years)
5. Yeast and E. coli genome completely sequenced . Patrick Brown of Stanford University
presented the 'gene chip' containing 6116 different gene specific sequences of the yeast g
enome . Ian Wilmut at Scotland's Roslin Institute presented"Dolly", a sheep cloned from
the cell of an adult mammary gland
6. (1999) Drosophila melanogaster (fruitfly) genome completely sequenced (175 Mb)
Future plans of molecular biology

Completion of the 2010 Project: the understanding the function of all genes within their
cellular, organismal and evolutionary context of Arabidopsis thaliana

Completion of the first computational model of a complete cell, or maybe even already
of a complete organism