Dna (1)

I0018* Property of STI
DNA and Genetics
 Mendel and Heredity
 DNA Structure and
Function
 DNA Technology
I0018
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Eiffel Tower
Paris, France
Petronas Towers
Kuala Lumpur,
Malaysia
Empire State
New York, USA
Burj Khalifa
Dubai, UAE
Image source: Google image search
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What is a blueprint?
Blueprint
Image source: jtanhueco.devianart.com
• Contains vital information
regarding the design
specifications such as the
size, numeric equations
involved, and the scope of
the type of construction to
be done
• Ensures that the
measurements are correct
so that the structure will be
well-built
• Contains the instructions on
how to build something
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DNA and Genetics
DNA is the Blueprint of Life
Image source: worldmag.com
Image source: dbriers.com
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DNA and Genetics
• Deoxyribonucleic acid
• Molecule that encodes all genetic
information used in growth and
functioning
• Every cell in the body contains DNA
which has all the information to
make a person who he/she is
• Most DNA molecules are double-
stranded helices, consisting of two
long biopolymers of simpler units
called nucleotides
What is DNA?
* Property of STI
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DNA and Genetics
• Each nucleotide is composed of
 Nucleobases (guanine, adenine,
thymine, and cytosine), recorded using
the letters G, A, T, and C
 Backbone made of alternating sugars
and phosphate groups, with the
nucleobases attached to the sugars
• Well-suited for biological information
storage, since the DNA backbone is
resistant to cleavage and the double-
stranded structure provides the
molecule with a built-in duplicate of
the encoded information
What is DNA?
* Property of STI
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DNA and Genetics
• Genetics is the branch of
science that deals with the
study of genes, heredity,
variations among organisms,
and DNA
What is DNA?
* Property of STI
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Mendel and Heredity
• Father of modern
genetics
• Born July 20, 1822
• Died January 6, 1884
• Botanist and a priest
• Researched on plants
(pea) to study about
heredity
Gregor Mendel (1822 - 1884)
Image source: en.wikipedia.org
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Terminologies
Mendel and Heredity
• Genotype – genes that are present in the
DNA of an organism
• Phenotype – what an organism looks like
as a result of the genotype and its
environment
• Allele – alternative form of the same gene
• Gamete – a reproductive cell
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Terminologies
Mendel and Heredity
• Heterozygous – condition in which two
alleles for a given gene are different from
each other
• Homozygous – A condition in which two
alleles for a given gene are the same
• Dominant traits – traits that are expressed
• Recessive traits – traits which are covered
up
• Probability – the chances that something
will occur
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How did Mendel’s Laws started?
Mendel and Heredity
• Mendel worked as a gardener and bee-
keeper during childhood
• He entered the monastery and from there,
his interest with the plants variation grew
• He used peas in his study because they
were available in many varieties,
reproduced quickly, and showed obvious
differences in their traits
• The use of peas gave Mendel control over
which plants mated
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Mendel and Heredity
• Mendel bred pea plants and recorded
inheritance patterns in the offspring
• He hypothesized that parents pass on to
their offspring separate and distinct
factors that are responsible for inherited
traits
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Mendel and Heredity
• He selected seven traits to study that each
occurred in different forms:
 Flower color – purple or white
 Flower position – axial or terminal
 Seed color – yellow or green
 Seed shape – round or wrinkled
 Pod shape – inflated or wrinkled
 Pod color – green or yellow
 Stem length – tall or dwarf
7 Traits of Peas Mendel Chose
Image source: http://www.wilson.wynric.org
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Mendel’s Steps in Breeding Peas
Mendel and Heredity
• Chose purple and white flowers as parent 1 and
parent 2
• Removed stamen (male reproductive organ in plants)
from parent 1 to prevent self-fertilization
• Transferred pollen from stamen of parent 2 to carpel
(female reproductive organ in plants) of parent 1
• Pollinated carpel matured into a pod containing
seeds (peas)
• Planted seeds from pod
• Examined offspring which are all purple flowers
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Mendel’s Steps in Breeding Peas
Mendel and Heredity
• The resulting hybrid offspring was called the first filial
or F1 generation
• The F1 generation resulted in all purple flowers
• He then allowed the F1 plants to self pollinate and
referred to the offspring as the F2 generation
• This time, he noticed a 3:1 ratio of purple and white
flowers
• Mendel then realized that this was the key to
understanding the basic mechanisms of inheritance
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Mendel’s Conclusions
Mendel and Heredity
• From his experiments, he came to three
important conclusions:
• The inheritance of each trait is determined by
“factors” that are passed on to descendants
unchanged
• The individual inherits one such factor from each
parent for each trait
• A trait may not show up in an individual but can
still be passed on to the next generation
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Law of Dominance
Three Laws of Inheritance
• When two parents with different traits are cross-
bred, a dominant trait will appear
• The dominant traits from the seven traits he chose
were:
• purple (flower color)
• axial (position)
• yellow (seed color)
• round (seed shape)
• inflated (pod shape)
• green (pod color)
• tall (stem length)
• The other traits are called recessive traits
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Law of Segregation
• Allele pairs separate during gamete formation and
randomly unite at fertilization
• There are four main concepts in this idea:
 There are alternative forms of genes – a gene
can exist in more than one form
 For each trait, organisms inherit two alternative
forms of that gene, one from each parent
 When gametes are produced, allele pairs
separate leaving them with a single allele for
each trait
 When the two alleles of a pair are different, one
is dominant and the other is recessive
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Law of Independent Assortment
• Different pairs of alleles are passed to
offspring independently of each other
• New combinations of genes present in
neither parent are possible
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Punnett Square
Punnett Square
• A diagram that is used to predict an outcome of a particular
cross or breeding experiment
• Named after Reginald C. Punnett, who devised the approach,
and is used by biologists to determine the probability of an
offspring's having a particular genotype
• A tabular summary of every possible combination of one
maternal allele with one paternal allele for each gene being
studied in the cross
• These tables give the correct probabilities for the genotype
outcomes of independent crosses where the probability of
inheriting copies of each parental allele is independent
• A visual representation of Mendelian inheritance
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Punnett Square
• B – Black (dominant trait)
• b – White (recessive trait)
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Punnett Square
• A pure bred black dog
with dominant black
alleles
• A pure bred white dog
with recessive white
alleles
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Punnett Square
• A black dog with a
dominant black allele
and a recessive white
allele
• A pure bred white dog
with recessive white
alleles
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Punnett Square
allele
allele
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Mendelian Genetics
Did you cheat
on me?! 
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Mendelian Genetics
Question # 1
A recessive allele (f) is responsible for a fire-breathing
dragon. A male dragon who does not breathe fire carries
this allele and reproduces with another dragon. One of
their four (4) hatchlings is a fire-breather. What are the
possible genotypes of the male and female dragon? Show
using a Punnet Square.
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Mendelian Genetics
Blending Theory of Inheritance
 Widespread hypothetical pre-Mendelian model of
inheritance
 No scientific basis
 Traits were passed on from parents to offspring like
a blended liquid solution
 Once traits have been mixed, they cannot be
separated anymore
 After lots of generations, the individuals would
arrive to a uniform appearance
Image source: en.wikipedia.org
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DNA Structures and Functions
Frederick Griffith’s Experiment
Image source: http://www.nature.com
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DNA Structure
 Composed of nucleotides which consists of a
phosphate group, a five-carbon sugar and a
nitrogenous base bonded together
 Each nucleotide has one of four nitrogenous bases:
o Adenine
o Guanine
o Thymine
o Cytosine
 Adenine and Guanine are called purine bases
 Thymine and Cytosine are known as pyrimidine
bases
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DNA Structure
 1940s: Erwin Chargaff found that a DNA
molecule contains the same amount of
adenine as thymine, and the same
amount of cytosine as guanine
 1953: James Watson and Francis Crick
worked out the actual structure of DNA
 Watson and Crick deduced that the DNA
molecule was arranged in the form of a
double helix
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DNA Structure
 The sides of the ladder are composed of
nucleotides with their nitrogenous bases pointed
toward the center of the ladder
 The rungs of the ladder are bonds between the
bases on the opposite sides
 Watson and Crick suggested that adenine only
forms a bond with thymine, and guanine only
forms a bond with cytosine
 If one side of the DNA molecule reads TTGACTA,
then the other strand must read AACTGAT
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DNA Structure
• The opposite sides of the helix are
antiparallel
• At the very end of each side of the
molecule is a nucleotide
• At one end, the phosphate group is the
very last molecule, while at the other end;
the sugar molecule is the last one
• Scientists have dubbed the end with the
phosphate group the 5' end, and the end
with the sugar the 3' end
• The 3' end on one side of the ladder is
opposite the 5' end on the other side
Image source: http://library.thinkquest.org/27819/ch6_3.shtml
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DNA Technology
Fields that have shown remarkable
growth from DNA Technology:
 Forensics
 Restriction fragment length
polymorphism (RFLP)
 Short tandem repeat
profiling (STR)
 Bioinformatics
 Pharmacology and
nanotechnology
 Archaeology and
anthropometry
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