this presentation gives the detailed information about the gene, and protein synthesis.

1. Concept of Gene And
Protein Synthesis
PRESENTED BY : SHITAL MAGAR
M.PHARM SECOND SEM
Department of Pharmacology
R.C Patel Institute of Pharmaceutical Education and Research,
Shirpur.

2.  The word ‘gene’ has two meanings: (1) the determinant of an observable trait or
characteristic of an organism, or (2) the DNA sequence that determines the chemical
structure of a specific polypeptide molecule or RNA molecule.
 The gene is operationally depened on the basis of four genetic phenomena: genetic
transmission, genetic recombination, gene mutation, and gene function.
 The word ‘gene’ was coined by W. Johannsen in 1909,but the modern concept of the
gene originated with Gregor Mendel, who in the 1860s studied the inheritance of
Characteristics on true-breeding varieties of garden peas.
What is Gene ? ( Petter Portin 2002 )
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3. Classical concept of Gene?
Neoclassical concept of Gene?
 Avery et al. (1944) demonstrated that the substance causing transformation in
bacteria was DNA. Transformation had been discovered by Griffith (1928), He
observed that killed bacterial cells injected into mice were able to transform
genetically different living bacteria into their own kind.
 The classical view of the gene begins with the work of Mendel (1866), in
which he explained definitively the transmission of genes or elements as he
called these units of inheritance .
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4. The Present Concept
of Gene
 Singer and Berg (1991) have pointed out that many different definitions of the gene are
possible. If we want to adopt a molecular definition, they suggest the following definition: “A
eukaryotic gene is a combination of DNA segments that together constitute an expressible
unit”.
 Each gene includes one or more DNA segments that regulate the transcription of the gene and
thus its expression'' Thus the segments of a gene include (1) a transcription unit, which
includes the coding sequences, the introns, the flanking sequences the leader and trailer
sequences, (2) the regulatory sequences.
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5. Summary of Conceptions of
Gene
YEAR, SCIENTIST GENE CONCEPT
1866 G.J. Mendel A unit factor that controls specific
phenotypic trait
1902 Sir A.E.Garrod One gene –one metabolic block theory
1940 Beadle & tatum One gene-one enzyme theory
1957 U.M.Ingram One gene-one polypeptide theory
1999 Griffiths & neumann Molecular and evalutionary gene
theory
2006 Griffiths & stotz Nominal gene theory
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6. Structure of Gene Merrick,1994
 Gene structure is the organisation of specialised sequence elements within
a gene. In most organisms, genes are made of DNA, where the particular
DNA sequence determines the function of the gene.
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7. Chromosome, DNA and Gene 7

8. DNA and RNA
Components DNA RNA
Sugar Deoxyribose Ribose
Bases A,G,C,T A,G,C,U
Strands Double strands Single strand
Genetic material Most life Some viruses
Enzyme None Many with
Structure Double helix linear or folded
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9. Types of RNA
 Messenger RNA (mRNA) copies DNA’s code & carries the genetic
information to the ribosomes.
 Ribosomal RNA (rRNA), along with protein, makes up the ribosomes.
 Transfer RNA (tRNA) transfers amino acids to the ribosomes where
proteins are synthesized.
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10. What is Gene Expression ?
 The process by which a gene's information is converted into the structures and
functions of a cell by a process of producing a biologically functional
molecule of either protein or RNA (gene product) is made.
 Gene expression is assumed to be controlled at various points in the
sequence leading to protein synthesis.
TRANSCRIPTIO
N
TRANSLATION
PROTEI
N
RNADNA
m-RNA degradation
control
RNA processing
control
RNA transport and
location control
Protein activity control
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11. What is Gene Expression ?
 Jacob and Monad (1961) studied control of protein synthesis in E. coli and lactose
digesting enzymes
 Genes can be switched on or off as necessary
 A gene that is ‘on’ will be transcribed
 In E.coli, the enzyme lactase will be produced if the gene ‘on’
 If the gene is ‘off’ mRNA will not be created and translation can not occur
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12. What is Gene Expression ?
 The operon model,
 Proposed by Jacob and Monad.
 Explains how genes switch on and
off.
 Operon=promoter, operator and
structural genes.
 Lac operon is found in E.coli.
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13. How Gene is Express ? 13

14. How Gene is Express ? 14

15. Types Of Gene
 On the basis of their behaviour the genes may be categorized
into the following types:
 i) Basic genes: These are the fundamental genes that bring about
expression of particular character.
 ii) Lethal genes: These bring about the death their possessor.
 iii) Multiple gene: When two or more pairs of independent genes act
together to produce a single phenotypic trait.
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16.  vi) Cumulative gene: Some genes have additive effects on the action of
other genes. These are called cumulative genes.
 v) Pleiotropic genes: The genes which produce changes in more than one
character is called pleiotropic gene.
 vii) Inhibitory gene: The gene which suppresses or inhibits the expression of
another gene is called inhibitory gene.
Types Of Gene 16

17. 17

18. Protein…..
 Proteins are single, unbranched chains of amino acid monomers
 There are 20 different amino acids.
 The amino acid sidechains in a peptide can become modified, extending
the functional repetoire of aminoacids to more than hundred different
amino acids.
 A protein’s amino acid sequence determines its three-dimensional
structure (conformation).
 In turn, a protein’s structure determines the function of that protein.
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19. Structure Of Protein 19

20. Protein Synthesis: An Overview
 Genetic information is contained within the nucleus of a cell.
 DNA in the nucleus directs protein synthesis but protein synthesis occurs in ribosomes
located in the cytoplasm.
 How does a ribosome synthesize the protein required if it does not have access to DNA.
 Information is copied from DNA into mRNA, this is transcription.
 mRNA leaves the nucleus and enters the cytoplasm of the cell.
 Ribosomes use the mRNA as a blueprint to synthesize proteins composed of this is
translation.
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21. The central dogma of protein
Synthesis
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22. Protein Synthesis 22
Nucleus
DNA
Transcription
Intron
Intron Pre-mRNA
mRNA
Nuclear pore
Export
Translation
Cytoplasm
Protein

23. Genetic Code Millard Susman,2001
 Proteins are composed of 20 different amino acids.
 A sequence of 3 nucleotides is used to code each
amino acid.
 Each triplet of nucleotides is called a codon.
 Start codon AUG codes for amino acid methionine.
 3 stop codons
 There are 64 codons in the genetic code 43=64
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24. Characteristics of the Code
 Continuity - The genetic code reads as a long series of three-letter
codons that have no spaces or punctuation and never overlap.
 Redundancy – Several different codons can code for the same amino
acid, but no codon ever has more than one amino acid counterpart.
 Universality – the genetic code is the same in almost all living organisms,
from bacteria to mammals
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25. Transcription
 Once the RNA polymerase leaves the promoter region, a new RNA
polymerase can bind there to begin a new mRNA transcript.
 Since prokaryotes lack a membrane bound nucleus translation can begin
even before the mRNA dissociates. However the pre-mRNA from
eukaryotic cells needs some modification before it leave the nucleus.
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26. Transcription: Initiation
 RNA polymerase binds to a segment of DNA and opens up the double helix
 RNA polymerase recognizes the promoter region which is a sequence of DNA rich in A
and T bases (TATA box) found only on one strand of the DNA.
 An RNA polymerase cannot recognize the TATA box and other landmarks of the promoter
region on its own. Another protein, a transcription factor that recognizes the TATA box,
binds to the DNA before the RNA polymerase can do so.
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27. Transcription: Initiation
 For transcription to be initiated, both promoter sequences must be present in their correct
locations. The nucleotide sequences in the promoters are slightly different from one
another, which means the RNA polymerase will bind in only 1 orientation, thus RNA
polymerase can only face 1 way during transcription. This ensures transcription will
proceed in only 1 direction.
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28. Transcription: Elongation
 The RNA polymerase uses only one of the strands of DNA as a template for
mRNA synthesis. This is called the template strand or sense strand. The coding
strand or anti-sense strand contains the complementary nucleotide sequence
to the sense strand.
 RNA polymerases can add nucleotides only to the 3’ end of a DNA sequence.
Thus, an RNA molecule elongates in the 5’ to 3’ direction. Consider the
following DNA sequence 3’ TACTTACTCGTCTTG 5’.
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29. Transcription: Elongation 29

30.  As the RNA polymerase
molecule passes, the DNA helix
re-forms. Synthesis continues
until the end of a gene is
reached where RNA polymerase
recognizes a terminator
sequence.
Transcription: Termination 30

31. Translation
 After transcription mRNA exits the nucleus via nuclear pores and ribosomes bind to
mRNA
 Ribosomes synthesize different proteins by reading the coding sequence on mRNA
 The mRNA is read in triplets of nucleotides each of which encodes an aa.
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32.  Consider the following mRNA sequence: 5’ AUGAAUGAGCUGAAC 3’
Translation 32

33.  Each active ribosome has 3 different binding sites for tRNA molecules: the P
(peptide) site, which holds one tRNA and the growing chain of amino
acids; the A (acceptor) site, which holds the tRNA bringing the next amino
acid to be added to the chain; and the E (exit) site, which releases the tRNA
molecules back into the cytoplasm.
Ribosomes 33

34. Ribosomes
 The anticodon of an aa-tRNA molecule binds to the mRNA codon exposed in the A site.
 Enzymes catalyze the formation of a bond between the last aa on the lengthening polypeptide and
the new aa. The polypeptide chain is transferred from the tRNA in the P site to the tRNA in the A
site.
 The ribosome moves down the mRNA strand, shifting the binding site a distance of 3 nucleotides
(1 codon), this is called translocation. A new A site is exposed as the tRNA that was in the P site
is moved to the E site and released.
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35. Ribosomes 35

36. Termination of Protein Synthesis
 Translocation of the ribosome exposes a stop codon in the A site. Stop
codons do not code for an aa, there are no corresponding tRNAs.
 A protein called a release factor binds to the exposed A site causing the
polypeptide to separate from the remaining tRNA molecule.
 Ribosome falls of the mRNA and translation stops.
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37. Termination In Protein Synthesis 37

38. Recent Advances
 Recent advances in producing and selecting functional proteins by using cell-free
translation.
 Recent advances of protein microarrays.
 Recent advances in dynamic m6A RNA modification.
 Recent advances of DNA Microarray Technology.
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39. References
 Genes: VII - Benjamin Lewin - Google Books ,oxford university,edition-VII,pp.156-158
 Rusmini, F., Zhong, Z. and Feijen, J., 2007. Protein immobilization strategies for protein
 biochips. Biomacromolecules, 8(6), pp.1775-1789.
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 Susman, M., Genes: Definition and Structure. eLSLaland, K.N. and Brown, G.R., 2011.
 Sense and nonsense: Evolutionary perspectives on human behaviour. Oxford University Press
Horowitz, N.H., 1995.
 One‐gene‐one‐enzyme: Remembering biochemical genetics.
 Protein Science, 4(5), pp.1017-1019. Portin, P., 1993.
 The concept of the gene: short historyand present status. The Quarterly Review of Biology, 68(2),
pp.173-223. Merrick.
 Hershey, J.W., 1996. 2 The Pathway and Mechanism of Eukaryotic Protein Synthesis. Cold Spring
Harbor Monograph Archive, 30, pp.31-69.
 Hartl, D.L. and Ruvolo, M., 2011. Genetics. Jones & Bartlett Publishers.