In this presentation, you can find introduction to basic molecular biology. you can learn what is molecular biology, central dogma of life, DNA, gene, characteristics and types of gene, alleles, history of molecular biology and human genome project

1. Molecular Biology
Lecture # 1
Introduction to Molecular Biology
Ms. Seerat-e-Fatima
M.Phil. Molecular Biology

2. Molecular Biology
• Molecular Biology is the branch of biology that deals with the study of
gene structure and function at molecular level
• The field of molecular biology overlaps with other fields especially
genetics and biochemistry.
• Molecular biology deals with the study of Central Dogma of Life
(DNA RNA Protein)
Transcription Translation

3. Central Dogma of Life

4. Introduction to Gene
• Introduction: In 1865, Gregor Mendel was the first one to describe
the elements of hereditary i.e., Gene. His observations and analysis of
the observation features of Peas led him to believe that specific traits
were passed on unchanged from parent plant to the next generation.
• Definition: Gene is a Greek work that means “to become” or “to
grow”. Genes make up the parts of DNA, acts as RNA instructors and
to make molecules called Protein.
• In humans, genes ranges in size from a few hundred to up to 2 billion
bases. Some genes are same in most people whereas some genes are
slightly different between different people

5. Characteristics
• Genes are the true carriers of heredity, responsible for the development
and structure of human body. They are physical substances passed on from
parents to children. The parents’ genes, in turn, have come from their
parents, grandparents and ancestors.
• Some genes are dominant, some are recessive.
• Genes do not act alone, they are influenced by genetic background of the
individual, and the external and internal environment.
• Each human somatic cell has around 30,000 genes present inside nucleus.
Some non-nucleated gene are also located inside the mitochondria in the
cell.

6. Terms associated with Gene
• Gene : A section of DNA that codes for specific trait.
• Trait : A trait is a specific characteristic that is unique. Traits determine how we
look, or how are body functions. They are inherited e.g., hair color, eye color,
etc.,
• Allele : Alternate form of gene are termed as alleles. The one pair of allele that
masks the effect of other when present in same cell is called dominant allele. The
allele that is masked by the other pair in the same cell is called the recessive
allele and is capable of producing a phenotype in organism only when two alleles
are present and identical.
• Locus : A fixed position of the chromosome where a certain gene resides.
•
• Exons and Introns : Most of the genes consists of short coding sequences called
exons, interrupted by short intervening non-coding sequences called introns.

8. History
• Introduced by Sutton in 1902 and elaborated by T.M Morgan in 1913 who
put forward gene theory that stated
“Chromosomes are bearer of hereditary units, and each chromosome carries
hundreds or thousands of genes. The genes are arranged on the
chromosomes in the linear order and on the special regions called locus”
• Features outlined by Bridge (1923), Muller (1927) and other scientists are
as follows:
Discrete particles inherited in mendelian fashion
Occupies a definite locus in chromosome
Responsible for expression of specific phenotypic character

9. Summary of evolution
Year Scientists Gene Concepts
1866 G.J. Mendel A unit factor that controls specific
phenotypic trait
1909 A.E. Garrod One gene – one product
1940 Beadle and Tatum One gene – one enzyme
1957 U.M. Ingram One gene – one polypeptide theory
1960s C. Yanofsky and co-workers Gene is a unit of recombination

10. Types of genes
Based on genetic phenomena
• Gene as a unit of transmission or cistron : The part of DNA specifying
a single polypeptide chain is termed as cistron. A cistron can have 100
nucleotide pairs in length to 30,000 nucleotide pairs. It transmits
characters from one generation to another as unit of transmission
• Gene as a unit of recombination or recon : The smallest segment of
DNA capable of being separated and exchange with another
chromosome is called recon. A recon consists of not more than two
pairs of nucleotides
• Gene as a unit of mutation of muton : Muton is a smallest unit of
genetic material which when changed or mutated produces a
phenotypic trait. It is delimited to single nucleotide

11. Based on activity
• Constitutive/House keeping genes : The genes which are constantly expressing themselves in a cell
because their products are required for normal cellular activities are called house keeping genes. For
example, genes for glycolysis, ATP etc.
• Non-constitutive/luxury genes : The genes which activate only according to the requirement of cellular
activities e.g., genes for lactose
• Inducible genes : The genes are switched on in response to the presence of a chemical substance or
inducer, which are required for functioning of the product of gene activity
• Cumulative Gene : Some genes have different effects on the action of other genes. These are called
cumulative genes
• Pleiotropic Gene : The genes which produce changes in more than one character is called pleiotropic
gene
• Modifying Gene : The gene which cannot produce a character by itself but interacts with other to
produce a modified effect is called modifier gene
• Inhibitory Gene : The gene which suppresses or inhibits the expression of another gene

12. Functions of genes
• Control the morphology or phenotype of an individual
• Control the structure and metabolism of body
• Replication of genes is essential for cell division
• Genes carry the hereditary information from one generation to next
• Reshuffling of genes at time of sexual reproduction produces
variations

13. Human Genome Project
• 1990 : American geneticists started an ambitious quest to map and
sequence the entire human genome.
• 1999 : the final draft of human chromosome 22
• 2000 : the final draft of human chromosome 21
• 2001 : working draft of whole human genome
• 2004 : the finished sequence of euchromatin part of human genome.