Nucleic Acids (DNA & RNA)
• Composed of C O H N & P to form the
nucleotides.
• Nucleotides include:
- a 5 carbon sugar
- a phosphate group
- a nitrogen base ( 5 types)
1. Thymine ( T ) 4. Guanine ( G )
2. Adenine ( A ) 5. Uracil ( U )
3. Cytosine ( C )
Nucleic Acid con’t
• These nucleotides
(monomers) are
arranged to form the
(polymers) nucleic
acids DNA & RNA.
DNA (deoxyribonucleic acid)
• Long double-stranded
polymer that is twisted
forming a double
helix.
• The backbone of the
ladder-like molecules
are formed by
alternating sugar
(deoxyribose) &
phosphate units.
DNA con,t
• The rungs are formed by the
binding together of
complementary bases (A- T
& G - C) by hydrogen bonds
• DNA is located in the nucleus
of a cell.
• Is the genetic material, directs
protein synthesis, & replicates
itself before cell division
• Chromosomes are
structures in the
nucleus of a cell
that contain genetic
(DNA) information
that is passed on
from one
generation to
another
DNA the discovery of
• *1865- Gregor Mendel, working alone in Austria,
discovers that some characteristics are inherited in
‘units’.
• 1870- Friedrich Miescher isolates chemicals from the
cell nucleus, including ‘nucleic acids’.
• 1879-Walter Flemming describes behavior of
chromosomes during cell division, implicating these
nuclear structures in inheritance.
• 1900- Hugo DeVries and others rediscover Mendel’s
work and establish first laws of inheritance.
• *1909- Wilhelm Johannsen coins the term ‘gene’.
The History of DNA continues!!!
• 1910- Thomas Hunt Morgan is the first to show that genes
are arranged in a linear fashion along chromosomes.
• 1928- Frederick Griffith uses a chemical extract to convert
harmless pneumonia bacteria into pathogenic forms nature
of this ‘inheritance factor’, however, is unknown.
• *1929- Phoebus Levene discovers that a sugar, deoxyribose,
is present in nucleic acids. Later identifies that DNA is
made up of nucleotides, a chemical unit comprising a
deoxyribose sugar, a phosphate group and one of four small
organic molecules known as nitrogen bases.
Rome wasn’t built in one day
• 1941- George Beadle and Edward Tatum show
that genes direct the production of proteins.
• *1943-William Astbury makes the first X-ray
diffraction images of DNA.
• 1944- Oswald Avery and colleagues show that
DNA can ‘transform’ cells cementing the link
between DNA and genes. His team determines
that genes are composed of DNA.
• *1950-Edwin Chargaff discovers that there are
patterns in the amounts of the four bases in DNA:
the amounts of G and C, and of A and T, are
always the same.
Still Building Rome !!!!!
• 1951- Linus Pauling and Robert Corey determine
that the structure of a class of proteins is a helix.
• 1960 – Sydney Brenner and other scientists show
the existence of messenger RNA.
• 1977 – Walter Gilbert, Allan Maxam, and
Fredrick Sanger develop methods to read the
DNA Sequence.
• 2000 – Human Genome Project an attempt to
sequence all human DNA is essentially complete.
The Discovery of DNA continues.
• *1952- Rosalind Franklin
and her colleague, Maurice
Wilkins takes her first Xray diffraction pictures, and
she writes a paper
proposing that DNA is so
thick that it is probably
doubled.
• *1953- James Watson and
Francis Crick publish first
paper proposing a double
helix structure for DNA.
James Watson and Francis Crick
Rosalind Franklin's X-ray diffraction photograph of DNA, 1953
DNA Review
•
•
•
•
•
•
•
Nucleotides include:
- a 5 carbon sugar
- a phosphate group
- a nitrogen base ( 4 types)
1. Thymine ( T ) 3.Guanine (G)
2. Adenine ( A ) 4. Cytosine ( C )
These nucleotides (monomers) are
arranged to form the (polymers) nucleic
acids DNA & RNA.
• The bases are grouped as purines
and pyrimidines
• Purines= Adenine & Guanine
• Pyrimidines= Thymine, Cytosine
& Uracil (found only in RNA)
Prokaryote DNA versus Eukaryote DNA
PROKARYOTE DNA:
• Prokaryotes do not have a nucleus so there DNA
is found in the cytoplasm.
• Most Prokaryotes have a single circular DNA
molecule that contains nearly all the cell’s
genetic information.
• Prokaryotes have about 1000 times less DNA
than an Eukaryote. (although an E coli
bacterium’s DNA contains approximately
4,639,221 base pairs)
Prokaryote DNA versus Eukaryote DNA
continued…
EUKARYOTE DNA:
• Eukaryotes DNA is a bit more complicated, 1000 X
more than Prokaryotes and is found in the nuclei of the
cell in the form of a number of chromosomes.
• The nucleus of a human cell contains more than 1 meter
of DNA (coiled into 46 tiny chromosomes!)
• Eukaryotic chromosomes contain both DNA and
protein, tightly packed together to form a substance
called Chromatin.
More on Eukaryotic DNA…
• Chromatin consists of DNA that is tightly
coiled around proteins called Histones.
• Together the DNA and histone molecules
form a beadlike structure called a
Nucleosomes.
• Nucleosomes seem to be able to fold
enormous lengths of DNA into the tiny
space available in the cell nucleus.
DNA Replication
• The use of existing DNA as a
template for the synthesis of new
DNA strands
• DNA replicates by "unzipping" along
the two strands, breaking the
hydrogen bonds which link the pairs
of nucleotides. Each half then serves
as a template for nucleotides
available in the cell which are joined
together by DNA polymerase.
More on DNA Replication…
• The double helix structure of DNA explains how DNA
could be copied or duplicated.
• Each strand (side) has all the information needed to
reconstruct the other half by the mechanism of base
pairing.
• In Prokaryotes replication begins at a single point in the
chromosome.
• In Eukaryotes replication occurs at hundreds of places.
• Replication proceeds in both directions until each
chromosome is completely copied.
• The sites where separation and replication occur are
called replication forks.
DNA Polymerase
• Is the principal enzyme involved in DNA
replication.
• It joins individual nucleotides to produce a
DNA molecule, which is, of course, a
polymer.
• It also “proofreads” each new DNA strand,
helping to maximize the odds that each
molecule is a perfect copy of the original
DNA.
RNA (ribonucleic acid)
Is different than DNA because:
• Single strand of nucleotides.
• Uracil replaces thymine
• its sugar is ribose instead of
deoxyribose.
• Involved in protein synthesis
• found in nucleus, cytoplasm & at
the ribosomes of a cell.
• Has 3 types: messenger RNA,
Transfer RNA, Ribosomal RNA
3 Types of RNA
1. Messenger RNA – (mRNA) carries copies of the
instructions for assembling amino acids into
proteins to the ribosome. Serve as messengers
from the DNA to the rest of the cell.
2. Transfer RNA – (tRNA) transfers each amino
acid from the cytoplasm to the ribosome as it is
specified by the coded messages in mRNA.
3. Ribosomal RNA – (rRNA) make up ribosomes
in conjunction with several dozen proteins.
Protein Synthesis
• The process by which the
genetic code puts together
proteins in the cell.
• Both DNA and RNA is
used to carry-out this
process.
• There are two parts of
protein synthesis
-transcription
-translation
Transcription (DNA Transcription)
• Process by which one part of the
nucleotide sequence of DNA is copied
into a complementary sequence of
RNA.
• Takes place in the nucleus of a cell.
• During Transcription, RNA
polymerase binds to DNA and
separates the DNA strands. RNA
polymerase then uses one strand of
DNA as a template from which
nucleotides are assembled into a
strand of RNA.
Transcription (DNA Transcription)
• RNA polymerase doesn’t bind to DNA just
anywhere to start copying DNA.
• The enzyme will bind only to regions of DNA
known as Promoters, which have specific base
sequences. So in effect they are signals in the
DNA to tell the enzyme where to bind, there
are also signals in the RNA to stop
transcription.
• DNA sequence is copied into a functional
RNA (mRNA) "messenger RNA"
Transcription (DNA Transcription)
• Once the RNA is copied from the DNA it has to be
finished.
• DNA had 2 different types of sequences of
nucleotides: Introns and Exons
• Introns are not involved in coding for proteins.
• Exons are the codes for building proteins.
• So to finish the RNA into the message for building
proteins the Introns are cut out and the Exons are
spliced together to form mRNA.
• The coding mRNA sequence can be described as a
unit of three nucleotides called a codon.
Translation (protein synthesis)
• The mRNA leaves the nucleus and
travels to the cytoplasm, where it
encounters cellular bodies called
ribosomes.
• The ribosome binds to the mRNA
at the start codon (AUG) that is
recognized only by the initiator
tRNA the anticodon.
• The ribosome proceeds to the
elongation phase of protein
synthesis which takes place in the
cytoplasm of the cell.
Translation continues.
• The ribosome moves from codon
to codon along the mRNA.
Amino acids are added one by
one, translated into polypeptide
chain forming a protein.
• At the end, a release factor binds
to the stop codon, terminating
translation and releasing the
complete polypeptide chain from
the ribosome.
PROTEIN SYNTHESIS DRAWING
ASSIGNMENT -- USE PAGES 301, 305 AND
306 TO HELP YOU
1.Draw and label protein synthesis include both
procedures of transcription and translation together as
one complete process
2.Must be done on one page
3.Required parts and structures include:
-nucleus
-ribosome's
-cytoplasm
-DNA ( deoxyribose, phosphate, adenine,
thymine, cytosine, and guanine)
-RNA: both mRNA and tRNA ribose, phosphate,
adenine, uracil, cytosine, guanine, codon, and anticodon
-amino acids: (example = val, phe or ala) pg 303
- polypeptide chain
Protein Review
• Proteins are made from amino
acids
• There are 20 different types of
amino acids that are used to
make proteins. ( much like the
letters of the alphabet are used to
form words)
• Chains of amino acids linked by
peptide bonds called
polypeptides
Genetic Coding
• Since RNA is constructed from
four types of nucleotides, there are
64 possible triplet sequences or
codons (4x4x4). Three of these
possible codons specify the
termination of the polypeptide
chain. They are called "stop
codons". That leaves 61 codons to
specify only 20 different amino
acids. Therefore, most of the
amino acids are represented by
more than one codon.
Reading the Genetic Code
• To read the codon ACGRead A from the left-hand
side of the table
Read C across the top of
the table
Read G as the fourth line
in that block, on the righthand side of the table
• The codon ACG codes for
the amino acid thr
(threonine)
Chemical Reactions in Organic Compounds
(Dehydration Synthesis & Hydrolysis)
• Dehydration synthesis
is the process of
removing a hydrogen
atom and a hyrdoxyl
group (-OH) from two
combining
monosaccharides to
form a larger
disaccharide.
Hydrolysis
• Hydrolysis is the
reverse process, in
which water is
"split" in the process
of breaking
polysaccharides
down into smaller
saccharides.