Molecular Biology

FITRIANNISA F. ZUBAIDI

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 Learning Outcomes
Introduction to:
• moleculer biology
• moleculer techniques
• DNA recombination
• applications in medicine

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 Molecular Biology
• Molecular biology studies molecules and the molecular
mechanisms of living organisms, such as the molecular nature
of the gene and its mechanisms of gene replication,
mutation, and expression.
• Molecular medicine is really a broad field, where by physical,
chemical, biological and medical techniques are widely-used
to describe molecular constructions and mechanisms,
determine fundamental molecular (and genetic) errors
causing diseases, and to develop molecular interventions to
improve them.

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 Molecular Biology
• The study of the activities and interactions of our genes is referred
to as genomics, and the related study of protein activity is referred
to as proteomics.
• In these fields of study, molecular diagnostics examine our DNA,
RNA, and proteins to assess how they are functioning.
• Diseases disrupt the function of cells and, therefore, can be
detected and/or monitored by examining the molecular alterations
of DNA, RNA, or the proteins in patients’ tissues, fluids, or tumors,
or in the infectious agents themselves (e.g., viruses or bacteria) that
cause the disease.

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QUICK REVIEW

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 DNA
• DNA is composed of two interlocking, helical strands (the famous double
helix), each of which is a string of four chemical bases in varying
sequence: adenine (A), guanine (G), cytosine (C), and thymine (T).
• Base pairs:
– Adenine on one strand is paired with thymine on the opposite strand.
– Guanine is paired with cytosine

• Reference is often made to “nucleotides”, which are the basic structural

building blocks of DNA (and RNA), consisting of a base combined with a
sugar and a phosphate group. A strand of DNA, therefore, is a chain of
nucleotides.

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DNA

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An essential cellular function is DNA replication, in which the helix separates, each
strand is duplicated, and then the duplicate strands combine through base pairing.
This is how an exact copy of an individual’s DNA is transferred from one cell to another
during cell division so that every cell contains the same DNA.

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Genes produce RNA (ribonucleic acid) through a process called transcription,
which in turn directs the production of the proteins that make up the machinery
of our cells—and, consequently, the structures and functions of our bodies. We
refer to this protein production as the “expression” of the underlying genes.

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 Gene

Segments of the DNA strand that are functional,

ranging in size from a few hundred bases to more than 2 million bases.
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 Gene
• The complex specialization, or differentiation, of cells throughout
the body is a result of only specific genes being active in certain
cells at certain times, and therefore expressing proteins related
only to the functions of those cells.
• Differences in genes among individuals, and the differential
expression of those genes in a given individual, account for the
physiological diversity of our race, as well as many of our diseases
and health conditions.

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 Gene Variations and Mutations
• Each complete human DNA helix contains a sequence of about three billion base
pairs. The sequence of the bases is more than 99% identical in all people.
• The 1% of sequences that are variable is the genes responsible for the
differences/variations that occur among humans.

• A particular gene whose set of base pairs is typical of the population is termed the
“wild type” or “normal” gene sequence.
• Gene variants (deviations from the wild type) may or may not be clinically
significant.
• A gene variant present in >1% of the population is called a polymorphism and may
be considered “another normal variant”.

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 Gene Variations and Mutations
• For a given population, there are three sources of variation:
mutation, recombination, and immigration of genes.
• There are three kinds of gene mutations, which may be a change of
only one base or a long sequence of bases. These are:
(1) hereditary – a mutation that is passed from parent to child;
(2) de novo – new mutations that arise in the egg or sperm cell, or shortly
after fertilization, and so are repeated throughout the body; or
(3) somatic – those that arise during life from environmental causes or
through an error in DNA replication, and are typically present in
tumor cells.

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MOLECULAR MEDICINE

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 Molecular diagnostics
• When specific mutations, or sets of mutations, are known to be
biomarkers associated with a disease or condition, molecular
diagnostic tests can examine a patient’s genes to determine
whether those mutations are present.
• Molecular diagnostics therefore can:
– assess a person’s risk of developing a disease,
– determine whether a person is a carrier of a hereditary condition,
– screen for diseases that are present but not yet symptomatic, or
– provide a diagnosis of existing symptoms.

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Molecular diagnostics examine the molecules
in the cell, i.e. the DNA, RNA, or proteins, and
their role in human biology and disease.
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Ng and Pin, 2007
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Ng and Pin, 2007

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MOLECULAR TECHNIQUES

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DNA RECOMBINATION

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Recombinant DNA technology enables individual
fragments of DNA from any genome to be
inserted into vector DNA molecules, such as
plasmids, and individually amplified in bacteria.
Each amplified fragment is called a DNA clone.

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 RESTRICTION
ENZYMES

The restriction enzyme EcoRI makes

"sticky" ends.

Watson J, Gilman M, Witkowski J,

Zoller M: Recombinant DNA. New
York, W. H. Freeman and Co., 1992,
p. 71.)

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• The term recombinant DNA must
be distinguished from the natural
DNA recombinants that result from
crossing-over between homologous
chromosomes in both eukaryotes
and prokaryotes.
• Recombinant DNA here means an
unnatural union of DNAs from
nonhomologous sources, usually
from different organisms.
• Some geneticists prefer the
alternative name chimeric DNA.

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Steps:
1. Isolating DNA
2. Cutting DNA
3. Joining DNA
4. Amplifying recombinant DNA

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 Application in Medicine
• Producing proteins
– Insulin
– Human growth hormone
– Vaccines

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Thank You
FITRIANNISA F. ZUBAIDI

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