 The DNA unit known as nucleotide consists of a five-carbon sugar
(deoxyribose), a phosphate group, and one of 4 nitrogenous bases
(adenine, guanine, cytosine, thymine).
 DNA is formed of two strands of nucleotides combined in a specific
way, A with T and C with G.
 The strands run opposite, one goes from 5’ to 3’ while the other goes the
opposite way, from 3’ to 5’, making the double helix form known today.
 RNA unit consists of a five-carbon sugar, a phosphate group and one of
4 nitrogenous groups as well, the difference with DNA is:
 The sugar is ribose instead of deoxyribose
 In its bases instead of thymine uses uracil
 It is not a double strand but a single strand
 There are 3 types: messenger , ribosomal and transfer RNA
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 Known as semi-conservative
Parent DNA
replication
Daughter DNA
Each DNA strand of the
parent cell is used as a
template for the 2 daughter
cells’ DNA
DNA replication occurs
inside the nucleus of the cell
Daughter strands contain one
“old” and one “new” strand.
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 Is the process by which the information in the DNA is
copied into a strand of messenger RNA (mRNA).
 What would have been thymine is changed to uracil in
RNA.
 Occurs inside the nucleus of the cell.
 Example:
5’ TTTAAACCCGGG 3’
DNA
3’ AAAUUUGGGCCC 5’ mRNA
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 Is the change from a chain of nucleotides to that of





amino acids, forming proteins.
Occurs in the ribosomes.
Ribosomes are made of protein and rRNA, and have 2
subunits.
The mRNA passes between the subunits and it is
“read” by the ribosome. A codon is made of 3 bases.
tRNA has anti-codons that complement the codons
and it carries the amino acid correspondent to it.
As the mRNA is read, the amino acids attach to each
other forming a chain which will become a protein.
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 1- tRNA carries the
amino acid to the
ribosome
3
1
 2- The anticodon of
the tRNA is
complementary to
the codon of the
mRNA
 3- As the tRNA
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moves along the
ribosome it releases
the amino acid
already attached to
the prior one.
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 In a blender the banana is
combined with 250 ml
deionized water and blended
for a few seconds.
 25 ml of a soap solution and
25 ml of a meat tenderizer
solution are then added to
the banana mixture and
mixed gently.
 The solution is then heated
until it simmers, and filtered.
Meat tenderizer and soap are used in the breaking of
the cell and nuclear membranes. It is heated to
accelerate the process.
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 10 mL of the filtered solution is
put in a test tube
Ethanol
DNA
 Ice cold 95% ethanol is added to
the tube, gently. DNA is not
soluble in alcohol, this causes it
to come out of solution.
Filtrate
layer
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 DNA fragments can be cut by enzymes and then separated
by a procedure called gel electrophoresis. Restriction
endonucleases or restriction enzymes (REs) are enzymes
obtained from bacteria that physically cut DNA.
 RE’s recognize a 4- or 6-base pair sequence known as
palindrome and cut the DNA in the same way every time.
 Some cut through the complementary strands at the same
position, producing blunt ends. Others cut it unevenly
producing sticky ends.
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 Blunt ends
Haemophilus aegyptius (bacteria) produces a restriction enzyme, Hae III that
recognizes the palindrome …GGCC… and cuts between the G and the C producing
blunt (or flush) ends.
…G G C C…
…C C G G…
…GG
…CC
+
CC…
GG…
 Sticky ends
Escherichia coli RY13 (bacteria) produces a restriction enzyme, EcoR I that
recognizes the palindrome … GAATTC… and cuts between the G and the A
producing sticky (or staggered) ends.
…G A A T T C…
…C T T A A G…
…G
+
…GTTAA
AATTC…
G…
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 Electrophoresis is the process
of applying voltage to a
solution of charged molecules
(DNA or proteins).
 Fragments of DNA obtained
by the use of REs are used to
identify individuals.
 Agarose is used to make a gel
where wells are made and the
DNA is placed in them.
 An electric field is applied
and DNA moves to the
positive electrode, since DNA
is negatively charged.
wells
Agarose gel
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Source of electric current
Electrodes are used to create an
electric charge. DNA will move towards
the positive one.
+
Agarose with wells filled with DNA for testing
(outlined by the pink rectangle) is submerged in
a conductor of electricity for at least one hour.
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 The DNA fragments move at
different rates depending on
their size.
well
faster moving
fragments of DNA
 Small fragments migrate faster
than larger ones. Fragments of
the same size concentrate in one
group forming a band (thin line)
on the gel.
+
Slower moving DNA
fragments
DNA movement
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 Population: DNA of





the population of the
area
Victim: female victim
of rape
S/V: DNA of victim
and suspected rapist.
S1: suspect 1
S2: suspect 2
Which of the 2 you
think is the rapist?
Population
Victim
S/V
S1
S2
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 The red rectangle shows
Population
Victim
S/V
S1
S2
the DNA of the victim is
present in the S/V
sample.
 The black rectangles
shows the DNA of the
rapist coincides with
that of suspect 1,
concluding he is the
rapist.
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 Examples where this technique is used in:
 Parental disputes
 An African-American man in his will asked to be buried in the
President Jefferson’s family plot alleging to be a descendant of his, and
was denied by the Jefferson’s family. DNA testing proved he was
descendent of Thomas Jefferson and Sally Heming so the Jefferson
family had to allow it.
 Crime investigation
 Rapes, incest, murder, etc.
 Studies on evolution (how similar or different species are)
 Did you know 50% of your DNA is common with that of plants?
 Did you know we have at least 20 genes in common with
bacteria?
 Studies on inheritable diseases
 cystic fibrosis, Tay-Sacs, etc.
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 ABO blood type group is an example of multiple allele
system where 3 alleles determine the outcome.
 Follows the principles of co-dominance, in which the
presence of two non identical alleles result in the
expression of both.
 Red blood cells (RBC) have unique antigens on their
surface that identifies them as blood type A, B, AB or O.
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 Letter I represents the dominant gene and i is the
recessive. The exponential represents the blood type
present in it.
 Both dominant traits are expressed
 IAIA and IAi = group A
 IBIB and IBi = group B
 IAIB
= group AB
 ii
= group O
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 Rh factor is independent from ABO blood type group
 Behaves like a complete dominance
 DD, Dd = Rh +
 dd = RH –
 Example
 Possible genotype of blood type A+
 IAIADD
 IAIADd
 IAiDD
 IAiDd
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Blood type
Antigens
Antibodies
Possible
donors
A+
A and Rh
B
A+,A-,O+,O-
A-
A
B and Rh
A- and O-
B+
B and Rh
A
B+,B-,O+,O-
B-
B
A and Rh
B- and O-
O+
Rh
A and B
O+ and O-
O-
None
All
O-
AB+
A, B and Rh
None
All
AB-
A and B
Rh
AB-,A-,B-,O-
Not just anyone can give you blood. Your RBC have antigens on its surface, unique to
your blood type, and antibodies that will attack RBC of other blood types as those
have different antigens on their surfaces.
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 Equipment
Anti A
Blood sample
Chamber s
Anti B
Anti Rh
Reactants for group type and Rh
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 A drop of blood is placed in all of
the chambers.
 In the chamber named A,
coagulant for group A is placed, if
it is blood type A it will cause it to
coagulate.
 In the chamber B, a coagulant for
group B is placed, if it is blood
type B it will cause it to coagulate.
 In the chamber Rh, a coagulant
for the Rh factor is added, if the
blood is Rh+, it will cause it to
coagulate.
22
Notice the coloration in the wells,
it is not uniform or smooth.
That indicates coagulation.
Remember: coagulation indicates
positive for that group
This person is AB+
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Although the colors may seem different,
the texture is the same, no coagulation.
This person in O-
The End
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