Deoxyribonucleic acid

kissimmeemisologistBiotechnology

Dec 14, 2012 (4 years and 7 months ago)

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DNA and RNA

Nucleic Acids


Nucleic acids are made from nucleotide
monomers



A nucleotide has 3 groups


Phosphate


Ribose sugar


Nitrogenous base


The phosphate and the ribose combine to
form a long chain polymer with the
nitrogenous base sticking out to the side

Fig. 15
-
21, p. 321


There are two types of nucleic acids



DNA


D
eoxyribo
n
ucleic
a
cid


RNA


R
ibo
n
ucleic
a
cid


There are 5 nitrogenous bases


Adenine (A)


Guanine (G)


Cytosine (C)


Thymine (T)


Uracil

(U)


DNA and RNA each only use 4 of the 5 bases


DNA uses A, G, T, C


RNA uses A, G, U, C


DNA contains the whole genetic code for life
within each single cell



RNA codes for a single type of protein



Thus RNA is made from DNA


In the late 1850s a monk named Gregor
Mendel observed certain traits in plants



He noticed plants could pass along
information such as flower color from one
generation to the next


In the early 1900s chromosomes were found
in cells



Chromosomes

are structured DNA and only
visible when cells are preparing to divide


1953 Watson and Crick determined the base
pairing of DNA



A:T


G:C


Base pairing led to the discovery of the
structure of DNA being a double helix

DNA replication


When cells divide the
DNA must be replicated
so the new cell will also
have a copy


DNA to protein


DNA contains the code for each protein we
need to make


This code is called a “gene”


Each gene codes for a single polypeptide


For humans we have about 40,000 genes



This makes up 20% of our total DNA


Fig. 15
-
24, p. 323

Redundancy in protein coding

Genetic engineering


Restriction enzymes


cut DNA into smaller
fragments


These are naturally occuring enzymes found in
bacteria and viruses to protect their DNA from
foreign DNA


These enzymes cut DNA at specific sites where
there is an inverted repeat of DNA bases



CAGC
GAATTC
TGCACTG


GTCG
CTTAAG
ACGTGAC


Every time this sequence occurs in DNA the
enzyme will make a cut.



We can use this to our advantage

DNA fingerprints


When restriction enzymes are added to a
sample of human DNA it cuts the DNA into
smaller pieces


DNA has an overall (
-
) charge


A special technique can be used to separate
DNA by its charge and size


This is called Gel Electrophoresis


By using several
different restriction
enzymes, each person’s
DNA will be cut up into
different sized
fragments.


This makes up our DNA
fingerprint since each
person will create a
unique set of bands on
the gel.

Recombinant DNA


Restriction enzymes can
also be used to make
new strands of DNA



This allows us to make bacteria work for us as
little protein production factories


Many of the proteins we need to sustain life
can be produced by bacteria cheaper than we
can synthesize them in a lab

Diabetics


Diabetes is a well know problem for many
Americans


This disease revolves around the body’s
inability to produce insulin


Insulin is a very necessary enzyme that helps
get glucose into cells so they can make energy


Without insulin we would die


Until the early 80’s diabetics had to use pig
insulin


Humulin was produced from bacteria carrying
the human insulin gene and marketed in 1983


Less compatibility problems using Humulin
than pig insulin


Many other human products are now begin
produced by bacteria instead of being
harvested from animals


Human Growth Hormone


Bovine Growth Hormone


Epidermal Growth Hormone