5. Chromosome
• The term was coined by German scientists Schleiden, Virchow,
Butschli .
• The DNA molecule is packaged into thread-like structures known
as chromosomes.
• Each chromosome has a constriction point called the centromere,
which divides the chromosome into two sections or arms. The
short arm of the chromosome is labeled the ‘P’ arm and the long
arm of the chromosome is labeled as the ‘Q’.
• Human chromosomes divided into two types: Autosomes and
allosome, human cells have 23 pairs of chromosomes, or 46
chromosomes in total.
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6. Chromosome numbers in different organisms
46
8
42
78
Human Fruit fly
Monkey
Chicken
6
38
Cat
8. Gene
• Term was introduced by Danish Botanist, Wilhelm Johannsen
in 1905.
• Gene is the sequence of DNA or RNA that codes for a
molecule and it is the basic physical and functional unit of
heredity.
• Some genes act as instructions to make molecules called
proteins.
• Majority of organisms encode their genes in long strand of
DNA.
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9. Organization of gene
• Exons: Exons are the portion of gene sequence that codes for
amino acids.
• Introns: Introns are the non-coding sequence which separate
the coding sequence.
• TATA box: It directs important enzymes to the correct
initiation site for transcription and present in the promoter
region.
• Termination codon: The end of translation is signified by a
termination codon.
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10. Gene expression
Gene expression is the process in which the instructions in our
DNA are converted into a functional product, such as a protein.
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Gene expression
Specific information
mRNADNA Protein
TRANSCRIPTION TRANSLATION
(In nucleus) (In Cytoplasm)
12. The Central Dogma
• The Central Dogma is an explanation
of the flow of genetic information
within a biological system. It stated
that DNA makes RNA and RNA
makes Protein.
• It was first stated by Francis Crick
1958 which states that once
“information” has passed into
protein it cannot get out again.
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13. Genome
• A genome is the complete set of genetic information in an
organism. It provides all of the information the organism
requires to function. It consists complete set of DNA, including all
of its genes.
• The term genome was created in 1920 by Hans Winkler. The
name genome is the blend of the words gene and chromosome.
• The genome size is the total amount of DNA contained within one
copy of a single genome.
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14. Genomics
• Term Genomic was coined by Thomas H. Roderick in 1986.
• Genomic is the branch of molecular biology concerned with
the structure, function, evolution and mapping of genome
and sequences.
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15. Gene mapping
• Gene mapping describes the methods used to identify the locus
of a gene and the distances between genes.
• The essence of all genome mapping is to place a collection of
molecular markers onto their respective positions on the
genome.
It is of two types:
Genetic mapping
Physical mapping
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16. Gene mapping
Genetic mapping Physical mapping
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Arrangement of genes and
genetic markers on a
chromosome.
Genetic markers are RFLP,
VNTR etc.
Provide physical distance
between the gens located on a
chromosome.
18. Why genome mapping is important
• Gene map is the anatomy of human genome. It is a prerequisite to
understand functioning of human genome.
• Helps in analysis of the heterogeneity and segregation of human
genetic diseases.
• Helps to develop methods for gene therapy.
• Provides clinically useful information about linkage.
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19. Gene sequencing
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• It is the process of determining the precise order
of nucleotides within a DNA molecule. It includes any method or
technology that is used to determine the order of the four
bases—adenine, guanine, cytosine, and thymine.
• This sequencing was first proposed by Frederick Sanger in 1975,
by chain termination method or by dideoxy sequencing.
• Allan Maxam and Walter Gilbert developed the DNA sequencing
method by chemical modification in 1976.
21. Why gene sequencing is important
• Genome sequencing is important to obtain a blue print where
DNA directs all the instruction needed for cell development and
function.
• To study gene expression in human tissue, organ.
• DNA underlines almost every aspect of human health, both in
function and dysfunction.
• To study the human variations etc.
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22. Human genome project
• Human Genome Project was an international scientific research
project with the goal of determining the sequence of nucleotide
base pairs that make up human DNA, and identifying and
mapping all of the genes of the human genome.
• It was created by US government ( The Department of Energy).
• There are 3 billion base pairs present in human genome.
• Cost to sequence the first human genome was about $ 3 billion.
• And it took around 13 years to sequence the first human genome
( from 2000 – 2013 ).
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23. Applications
• Improved diagnosis of disease.
• Earlier detection of predispositions to disease.
• Rational drug design.
• Gene therapy and control systems for drugs.
• Organ Replacement.
• Also useful in DNA forensics to identify potential suspects at
crime scenes etc.
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24. References
• Markus N; “Definition of historical models of gene and their
relation to students’ understanding of genetics”; “Science and
education”; 5 December 2006; 16(8): 849-881.
• Barnett L, Breoner S; “General nature of the genetic code for
proteins” ; “Nature”; 1961; 192: 1227- 32.
• Woodson S A; “Ironing out the kinks: splicing and translation in
bacteria”; “Genes and development”; may 1998; 12(9) : 1243-7.
• Albert B, Johnson A; “Molecular biology of the cell”; “Garland”;
14 July 2014; 6th edition.
• Brosius J; “The fragmented gene”; “Annals of New York academy
of science”; 2009: 186-193.
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