This document outlines several modern biological techniques used in laboratories, including cell and tissue culture, centrifugation, chromatography, gel electrophoresis, spectrophotometry, polymerase chain reaction (PCR), DNA sequencing, immunoassays, DNA cloning, and microarrays. It provides brief descriptions of the basic principles and applications of each technique.

1. Preparation Techniques
and
Modern Biological Techniques

2. • Cell and Tissue Culture
• Centrifugation
• Chromatography
• Gel Electrophoresis
• Spectrophotometry
• Polymerase Chain Reaction
• DNA Sequencing
• Immunoassays
• DNA Cloning
• Microarrays

3. Cell and Tissue Culture
• Is the complex process by which cells • Tissue culture is the growth of
are grown under controlled conditions,
generally outside of their natural tissues or cells separate from the
environment. organism. This is typically
• Culture cells derived from multi-cellular facilitated via use of a liquid, semi-
eukaryotes, especially animal cells. solid, or solid growth medium,
However, there are also cultures of
plants, fungi and microbes, including such as broth or agar.
viruses, bacteria and protists. • Tissue culture commonly refers to
• Mass culture of animal cell lines is the culture of animal cells and
fundamental to the manufacture of
viral vaccines and other products of
tissues,
biotechnology i.e. drug discovery,
cancer biology, regenerative medicine
and basic life science research

4. Centrifugation
• The process of separating lighter portions of a solution, mixture, or
suspension from the heavier portions by centrifugal force.
• A laboratory centrifuge is a piece of laboratory equipment, driven by a motor,
which spins liquid samples at high speed.
– Where the centripetal acceleration is used to separate substances of
greater and lesser density.
•
• There are various types of centrifugation:
• Differential centrifugation, often used to separate certain organelles from
whole cells for further analysis of specific parts of cells
• Isopycnic centrifugation, often used to isolate nucleic acids such as DNA
• Sucrose gradient centrifugation, often used to purify enveloped viruses and
ribosomes, and also to separate cell organelles from crude cellular extracts

5. Chromatography
• Is the collective term for a set of laboratory
techniques for the separation of mixtures.
• The mixture is dissolved in a fluid called the
mobile phase, which carries it through a
structure holding another material called the
stationary phase.
• The various constituents of the mixture travel
at different speeds, causing them to separate.

6. Gel Electrophoresis
• Involves the separation of chemicals along a solid medium in the presence of an
applied potential difference.
• Chemicals such as blood proteins, DNA or inorganic ions can be separated
according to differences in their mass and/or charge. The solid medium used in
electrophoresis is usually an agarose or polyacrylamide gel
• Has uses in forensic science because it can be used to isolate and compare DNA,
blood proteins and inorganic substances such as gunshot residues from crime
scenes with suspects, victims or standard reference material.
– produce DNA fingerprints; DNA evidence from a crime scene can be compared
to DNA samples from different suspects, for instance, and suspects can either
be included or excluded from suspicion using the results of such tests

7. Spectrophotometry
• A method to measure how much a chemical substance
absorbs light by measuring the intensity of light as a beam of
light passes through sample solution.
• The basic principle is that each compound absorbs or
transmits light over a certain range of wavelength. This
measurement can also be used to measure the amount of a
known chemical substance.
• One of the most useful methods of quantitative analysis in
various fields such as chemistry, physics, biochemistry,
material and chemical engineering and clinical applications.

8. Polymerase Chain Reaction
• The polymerase chain reaction (PCR) is a biochemical technology in
molecular biology to amplify a single or a few copies of a piece of DNA
across several orders of magnitude, generating thousands to millions of
copies of a particular DNA sequence.
• Now a common and often indispensable technique used in medical and
biological research labs
– i.e. DNA cloning for sequencing,
– functional analysis of genes;
– diagnosis of hereditary diseases;
– identification of genetic fingerprints (used in forensic sciences and
paternity testing);
– detection and diagnosis of infectious diseases.

9. DNA Sequencing
• Includes several methods and technologies that are used for determining
the order of the nucleotide bases—adenine, guanine, cytosine, and
thymine—in a molecule of DNA.
• Knowledge of DNA sequences has become indispensable for basic
biological research, other research branches utilizing DNA sequencing, and
in numerous applied fields such as diagnostic, biotechnology, forensic
biology and biological systematics.
• Instrumental in the sequencing of the human genome, in the Human
Genome Project.
• Related projects, often by scientific collaboration across continents, have
generated the complete DNA sequences of many animal, plant, and
microbial genomes.

10. Immunoassays
• A specific type of biochemical test that measures the presence or concentration of a
substance (referred to as the "analyte") in solutions that frequently contain a complex
mixture of substances.
• Analytes in biological liquids such as serum or urine are frequently assayed (i.e., measured)
using immunoassay methods.
• In essence, the method depends upon the fact that the analyte in question is known to
undergo a unique immune reaction with a second substance, which is used to determine the
presence and amount of the analyte.
• This type of reaction involves the binding of one type of molecule, the antigen, with a second
type, the antibody. Immunoassays can be carried out using either the antigen or the antibody
in order to test for the other member of the antigen/antibody pair. In other words, the
analyte may be either the antigen or the antibody.
• Applied in measurement of blood levels of vitamins, hormones, etc. Also used in sports
anti-doping laboratories to test blood samples for prohibited human growth hormone.
• .

11. DNA Cloning
• The use of DNA manipulation procedures to
produce multiple copies of a single gene or
segment of DNA.

12. Microarrays
• A small solid support, usually a membrane or
glass slide, on which sequences of DNA are
fixed in an orderly arrangement.
• Used for rapid surveys of the expression of
many genes simultaneously, as the sequences
contained on a single microarray can number
in the thousands.

13. • Fixation – cutting of material into relatively tiny
pieces and soaking it in a fixative
• Staining – allows one to observe clearly structural
details of the specimen to be observed
- provides contrast through color that reveals
structural details undetected in other
preparations
- ex. of stains: iodine, methylene blue
• Computerized Axial Tomography (CAT Scan) –
uses a rotating beam of x-rays. Provides a
detailed picture of a human body

14. • Chromatography – separating and analyzing a
mixture of chemical substances
• Tissue Culture – growing living cells from
organisms in culture tubes filled with oxygen and
all necessary nutrients
• Centrifugation – separating materials of different
densities
• Mounting – prepare specimen for microscopic
examination, especially by positioning on a slide

15. • Dry Mount – most basic; position specimen on
slide and put on cover slip
- Dry Mount samples: hair, feather, pollen
• Wet Mount – suspend specimens in fluids like
water, immersion oil, etc.
- Wet Mount samples: aquatic samples, living
organisms, natural observations
• Smearing – the sample is spread on a slide
• Squashing – spreads specimens by pressure

16. • Fixative Agent – substance used for
preservation of tissue/cell specimens for later
examination
• Microdissection – dissection under
magnification
• Dehydration – extracting water from
tissues/cells through techniques like heating
or by using dehydrating agents like alcohols