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DNA &
Genetics in
Biotechnology
What is a DNA?
• A nucleic acid that carries the genetic
information in the cell and is capable of
self-replication and synthesis of RNA.
• DNA consists of two long chains of
nucleotides twisted into a double helix
and joined by hydrogen bonds between
the complementary bases adenine and
thymine or cytosine and guanine.
• The sequence of nucleotides determines
individual hereditary characteristics.
What is a Nucleotide?
• A single molecule of DNA comprised of 2
basic parts made from 3 distinct molecules.
– Sugar/Phosphate Backbone
– Nitrogenous Base
Sugar/Phosphate Backbone
• Comprised of deoxyribose sugar and a
simple phosphate molecule
• Forms a strong bond that creates the
backbone of a DNA strand
• EXACTLY THE SAME IN ALL DNA
Nitrogenous Base
• Bond with complimentary bases in other
nucleotides to form the rungs of the DNA
ladder (zip DNA together)
• Only 4 types in all DNA-Adenine, Cytosine,
Guanine, and Thymine
• Adenine and Thymine bond only with each
other
• Cytosine and Guanine bond only with each
other
DNA form
• DNA nucleotides combine in cells to form
long strands in the shape of a double helix
(looks like a twisted ladder)
DNA Form
• Nucleotides bond at two spots
– Sugar/Phosphate molecules form the backbone
(outside rails)
– Nitrogenous bases bond in the middle by hydrogen
bonds (steps or rungs)
– Hydrogen bonds between nitrogenous bases are
MOST EASILY BROKEN
• The order of the nucleotides is the
determining factor in the expression of
genes in organisms.
Characteristics of DNA
DNA
• Accounts for all genetic variation between
different individuals and organisms by the
use of different:
– Sequences of nitrogenous bases
– Lengths of DNA segments
– Numbers of Chromosomes and amounts of DNA in
an organism
• The amount of DNA in an organism DOES
NOT relate to the size or complexity of an
organism.
DNA Replication
• The process through which cells copy DNA
for transmission to daughter cells during
cell division.
– The double helix structure allows DNA to easily
unzip down the center between nitrogenous bases.
– Free floating nucleotides attach to each of the
separated DNA strands forming 2 new strands of
DNA, each an exact copy of the original.
DNA Replication
Mutations
• A mutation is an unexpected change in a
DNA sequence, usually occurring during
the replication/cell division.
• Mutations are common in most organisms
(especially simple organisms) though only a
small percentage produce noticeable
changes in organisms.
Genetic Hierarchy
Genetic Hierarchy
• A group of nucleotides=a gene/allele=45150 base pairs
• A group of genes=1 strand of DNA
• Several condensed strands of DNA=1
chromosome
• 2 chromosomes=1 chromatid pair
• All possible gene forms in a
population=Genome
Gene Mapping
• Mapping the genome of a species allows
scientists to identify beneficial and harmful
genes in a population, and is the first step
in determining the location of specific genes
on chromosomes.
– Changes in the genome of a species occur slowly
in response to environmental changes.
Transferring of DNA
• Polygenic traits are controlled by more
genes and therefore it is more difficult to
improve polygenic traits.
• DNA is passed to offspring during sexual
reproduction through single chromosomes.
Human Genetics
• Almost all humans have 46 chromosomes.
– Individuals with Down Syndrome have one extra
chromosome.
• Humans generally differ from each other by
approximately 3 million nitrogenous base
pairs, or 0.1% of the total gene sequence.
Genetic Disorders
Genetic Disorders
• Diseases or other problems resulting from
errors in the transmission of genetic
information, or the expression of certain
negative gene sequences.
Genetic Disorders
• Most genetic disorders are recessive, and
thus cannot be predicted without genetic
analysis
– Recessive disorders are transmitted by carriersparents with one dominant gene (normal) and one
recessive gene (disorder)
• Example-Tt
Genetic Disorders
• Certain disorders are more common in
certain populations
– Example: The occurrence of sickle
cell in African Americans.
Common Genetic Disorders
• Inherited Disorders
– Examples: Tay-Sachs, Sickle Cell Anemia,
Hemophilia
• Mutations
– Cancer-uncontrolled division of abnormal cells
– Treatment must destroy mutated cells
Genetic Mutations
• Sudden unexpected changes in the genetic
code of an organism which appear most
often during the process of replication
Genetic Mutations
• Often result from increased levels of stress
on cells just prior to or during cell division
• Stresses include-radiation, UV rays,
environmental, etc.
Genetic Mutations
• Almost all mutated cells die immediately, or
never impact living organisms
– Most mutations in humans are harmful such as
cancer
– A small fraction of noticeable
mutations are beneficial, such as
Chimeras which are used to give us
variegated plants.
Genetic Mutations
• Most mutations occur in developed plants
and animals, affecting isolated groups of
cells.
• Mutations are most devastating when the
occur in the early development of
organisms. (STEM CELL STAGE)
Types of Mutations
• Point mutation
– A mutation that changes DNA at a single point,
substituting one nucleotide pair.
• Frameshift
– Nucleotides are inserted or deleted, altering the
entire DNA sequence after the mutation
DNA Extraction and
Analysis
DNA Extraction
• The process of isolating nucleic acids
(DNA) from organic material.
• DNA can be extracted from almost any
intact cellular tissue (more cells make it
easier)
– Skin, blood, saliva, semen, mucus, muscle tissue,
bone marrow, etc.
– DNA cannot be extracted from hair, unless skin is
attached at the bottom
• Mitochondrial DNA can often be extracted
long after nuclear DNA has degraded.
Simple DNA Extraction
• For observation only, not feasible for
analyzing DNA
• Works well with fruit (Example:
Strawberries)
Simple DNA Extraction
• Step 1
– Physically break apart plant material, usually fruits
• Step 2
– Use a detergent to break apart the cell membrane
• Step 3
– Treat with ethyl alcohol to isolate DNA from
remaining proteins and sugars
• Step 4
– Spool using a glass rod to view a large clump of
nucleic acids (DNA)
Advanced DNA Extraction
• The organism to be tested is chosen, and a
sample is taken from which DNA can be
extracted.
• Detergents are used in simple DNA
extraction procedures to break down cell
membranes, blending the contents of the
cell.
Advanced DNA Extraction
• The DNA sample is treated with enzymes to
isolate nucleic acids, usually both DNA and
RNA
– Enzymes dissolve proteins, sugars, and other
materials
– Examples: protease, amylase, etc (enzymes end
with the suffix –ase)
• A second enzyme may be applied to cut
DNA into gene segments for analysis called
restriction enzyme
Restriction Digests and Enzymes
• Restriction enzymes are used to cut
extracted DNA into smaller gene
sequences.
– Make analysis easier during the process of gel
electrophoresis.
– Enables scientists to isolate specific genes with
specific enzymes for use in genetic engineering.
Restriction Digests and Enzymes
• Cuts the gene from the chromosome
making a sort of gene soup after the
removal of proteins
• Leaves the ends of gene segments “sticky”
with usually 3 exposed nucleotides on one
side of the double helix, so that ends may
be rejoined later.
Methods of DNA Analysis
• There are several simple methods used for
analyzing DNA
– Paternity Testing
– Gel Electrophoresis
• Advanced Methods
– Polymer Chain Reaction (PCR)
– Amniocentesis
Paternity Testing
• Simple method of DNA analysis that
compares the DNA of an offspring, plant or
animal, with a known mother and suspected
father.
Paternity Testing Process
• DNA sample taken usually from saliva or
blood in animals and leaf or callus tissue in
plants. (Hair does not contain DNA, but the
hair follicle does.)
• DNA isolated in sample through the use of
protein “eating” enzymes.
Paternity Testing Process
• Sample run on gels or through a gene
sequencer to indicate the presence of
certain genes.
• Comparison of genes-anything present in
the child MUST BE PRESENT IN EITHER
THE MOTHER OR THE FATHER. 13
genes present in the child that are not in the
mother, but present in the father make a
99% match.
Polymer Chain Reaction (PCR)
• Method used in forensic science to amplify
genetic material for identification or
analysis.
• Newer technique used only in advanced
laboratories.
• Only a few cells are needed with this
technique.
Amniocentesis
• Method used to analyze the DNA of a
mammal (occasionally other animals) prior
to birth.
• Used widely in humans to predict the
expression of lethal genes or genetic
disorders in high-risk pregnancies.
• Gaining favor in high expense animal
breeding (Ex. Race horses)
Gel Electrophoresis
• Method used to analyze extracted DNA
through the distribution of genetic markers
on an agar media.
• Smaller genes travel further distances on
the gel. Samples extracted through the
same process can be easily compared on a
single gel.
Gel Electrophoresis Process
• An agar gel is placed into a mold to dry,
then placed into an electrophoresis
chamber.
• DNA extraction is placed in small wells at
one end of the agar gel. Each well
represents a different sample or individual.
Gel Electrophoresis Process
• Low voltage direct current is run through a
buffer solution surrounding the agar gel
distributing DNA fragments across the gel
– Fragments separated by the size of the gene
segment; smaller move faster than larger
– Negative charged DNA fragments are repelled away
from the negatively charged wells to the positive
charged end.
Gel Electrophoresis Process
• Buffer solution provides a means of
transmission for electrical current, but also
keeps DNA samples in place in wells in the
gel.
– Buffer is heavier than DNA
Gel Electrophoresis Process
• Strength of the electrical current determines
the speed at which DNA moves across the
gel.
• Ethidium Bromide or another Bromine
based solution is applied at the end of the
electrophoresis process to stain DNA for
better viewing under certain bands of light.