Download Basic Review of DNA

Basic Review of DNA
Biomolecules
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These are the molecules that make up all
living things
Carbohydrates
Lipids
Proteins-chains of amino acids
Nucleic acids-chains of nucleotides
Elements
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99% of any living thing is made up of just
4 elements.
Carbon-C
Hydrogen-H
Oxygen-O
Nitrogen-N
Phosphorus-P
Carbohydrates
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Sugars such as glucose and starches
The function is to store energy
Made up of C,H,O
Lipids
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Fats and oils
The functions are energy storage,
insulation, protective cushion, and is the
main component of cell membranes
Made up of C, H, H
Proteins
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Structural proteins such as keratin,
enzymes like amylase, most hormones like
insulin
Functions include structure, growth,
development, and metabolism
Made of C, H, O, N
Nucleic Acids
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DNA and RNA
Storing hereditary information, directing
the production of proteins.
Made of C, H, O, N, P
How DNA is related to traits
DNA is protected in the nucleus of cells, it
has the directions for making proteins
DNA is transcribed into RNA which can go
out of the nucleus to the ribosomes (protein
factories)
RNA is read by the ribosomes and translated
into proteins
Proteins determine the traits you see.
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DNA – RNA – PROTEIN – TRAIT
Only 1% of the DNA leaves the nucleus of
the cell.
That 1% is responsible for making DNA a
factor in Forensic testing
Structure of DNA
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Made up of two chains of nucleotides
Each nucleotide has 3 subunits
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Deoxyribose sugar
Phosphate ion
One of four bases
Adenine
 Guanine
 Cytosine
 Thymine
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The two chains of nucleotides come
together to form a ladder.
The nitrogenous bases are the rungs of the
ladder
Sugars and phosphates are the outsides of
the ladder.
Adenine bonds with Thymine (Two bonds)
Guanine bonds with Cytosine(Three bonds)
Recombinant DNA
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When a genetic code is identified on a
strand of DNA as having the instructions
for a certain protein, biologists want to use
this protein for research and drugs.
A recombinant DNA is a sequence of DNA
that has been spliced at specific places to
use the natural chemical producing
abilities.
Restriction Enzymes
These are the enzymes that cut the
recombinant DNA.
They are special “scissors” that cut a specific
strand of the DNA molecule when it
recognizes the bases.
These pieces of DNA are introduced into
bacterial or animal cells that reproduce the
protein over and over.
Tandem Repeats
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This is a region of the chromosome that has
multiple copies of a core DNA sequence
that repeat constantly.
More than 30% of the human genome is
made up of these.
Seem to have no impact on genetic
function or appearance.
Restriction Fragment Length
Polymorphisms (RFLP)
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Different fragment lengths of base pairs
that result from cutting a DNA molecule
with restriction enzymes.
All humans have the tandem repeats but the
number of repeats differs greatly.
The first scientifically accepted protocol
for DNA typing in the USA
Polymerase Chain Reaction PCR
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This is a technique to copy and multiply DNA
strands.
Uses a DNA polymerase to synthesize a specific
region of DNA
Uses temperature to break bonds and stimulate
replication.
Better than RFLP, extremely sensitive. Has been
used to ID saliva on stamps, coke cans and
envelopes.
Short Tandem Repeats STR
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Locations on the chromosome that contain
short sequence elements that repeat
themselves within the DNA molecule.
Usually only 3-7 bases. Much shorter than
RFLP procedure.
STRs can be found in bodies and stains that
have been decomposed.
STR v/s Y-chromosome STR
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Amelogenin gene- gene for tooth pulp, is
shorter by 6 bases on X chromosome than
the Y chromosome.
Y chromosome is male specific and always
paired with the X
Very useful when more than one males is
involved in assault.
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Currently 20 different Y-STR markers have
been id. A test kit is avail for 6 Y-STR .
This is only from the male so when
looking at a DNA profile it will take out
lots of overlapping info.on the profile
Ex. A rape specimen: XX from female
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XY from 1st suspect
XY from 2nd suspect
Mitochondrial DNA
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Nuclear DNA is found only in nucleus and
contains 23 pairs of chromosomes
Mitochondrial DNA- mtDNA- outside the
nucleus and is inherited only from the mother.
The mitochondria are responsible for supplying
the energy of the cell.
Each cell in our body has 100 to 1000 of
mitochondria.
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Used in cases where the DNA is degraded such as
charred remains and small quantities like the hair
shaft
When a reference sample from a deceased or
missing person, they can get mtDNA from any
maternally related relative.However people with
the same maternal linkage are indistinguishable.
This testing is more sensitive than nuclear DNA
but is much more costly and time consuming.
The FBI has strict limits on the types of cases they
will accept these samples from.
Combined DNA index System
CODIS
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Allows crime labs to compare DNA types
recovered from crime scenes to DNA of
convicted sex offenders and convicted
criminals.
Uses 13 standard STRs
Collection procedures
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Biological evidence must be packaged in a
paper bag or well ventilated box, never in
an airtight container.
Must be refrigerated or stored out of direct
sunlight in a cool place, unless it is blood
mixed with soil which must be frozen
immediately
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Must collect 7cc of whole blood for a
reference or a buccal swab inside the
mouth. To be kept refrigerated.
Contamination can occur if the collector
sneezes or coughs during the collection .
Ways to prevent contamination
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Change gloves before each item
Collect a control
Pick up small items with forceps
Each piece of evidence gets its own bag