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DNA Chapter 10
The Code of Life
History
Griffith
Hershey and Chase
Chargaff
Linus Pauling
Maurice Wilkins
Rosalind Franklin
Francis Crick
James Watson
Model
Double Helix
Building Blocks-Nucleotides
Sugar-Deoxyribose
Phosphate
Nitrogen Base
Types of Nitrogen Bases
Pyrimidines and Purines
•DNA has four kinds of bases, A, T, C, and G
thymine
cytosine
adenine
guanine
Hydrogen bonds between
bases hold the strands
together
Each base pairs with a
complementary partner
A pairs with T
G pairs with C
DNA stands for_____________.
Describe the structure and replication of
DNA.
Describe Transcription.
Describe Translation.
DNA is made up of building blocks called
nucleotides. A nucleotide consists of a
phosphate, a sugar (deoxyribose) and a
nitrogen base.
There are two kinds of basespurines(adenine and guanine) and
pyrimidines(cytosine and thymine).
Purines have a double ringed structure
and pyrimidines have a single ringed
structure.
A pairs with T and they join
with a double hydrogen bond
and C pairs with G and they
join with a triple bond. DNA is
anti-parallel. Its structure is
called a double helix.
In DNA replication, the
strands separate.
Enzymes use each strand as a
template to assemble the new
strands
DNA replication begins at
specific sites
Each strand of the double
helix is oriented in the
opposite direction
DNA Replication
Where? Nucleus
When? before cell division so that each cell
can have a complete set of instructions
What? DNA, free nucleotides, enzymes and
energy
Enzymes (helicases) unwind the DNA. Then it
unzips beginning in the middle-points of
origin.
Free DNA nucleotides come in and join with
complimentary base on each strand.
Enzymes join the sides of the
new DNA strands.
Each strand is half old and
half new. Thus this process is
semi-conservative.
RNA vs DNA
Ribose-deoxyribose
RNA is single stranded and
DNA is double stranded
Uracil instead of thymine
A specific gene specifies a
polypeptide
The “words” of the DNA
“language” are triplets of
bases called codons.
The codons in a gene specify
the amino acid sequence of a
polypeptide.
Virtually all organisms share
the same genetic code
Transcription
Where? Nucleus
Why? DNA wants to send out a message.
What? DNA, free RNA nucleotides, enzymes
and energy
First, a section (gene) of DNA unzips.
Then RNA nucleotides come in and join with
the template side of the DNA.
Enzymes join the RNA nucleotides and the
RNA pulls away and leaves the nucleus.
DNA zips back up.
mRNA Editing
Exons-left in
Introns-cut out
Noncoding segments
called introns are
spliced out
A cap and a tail are
added to the ends
Translation (Protein Synthesis)
Where? At a ribosome in the
cytoplasm
What? enzymes and energy,
mRNA, tRNA, rRNA, amino acids
Transfer RNA molecules serve
as interpreters during
translation
In the cytoplasm, a
ribosome attaches
to the mRNA and
translates its
message into a
polypeptide
The process is aided
by transfer RNAs
Each tRNA molecule has a
triplet anticodon on one end
and an amino acid attachment
site on the other
Ribosomes (rRNA)
mRNA, a specific tRNA, and
the ribosome subunits
assemble during initiation
Translation
subunit joins mRNA at a start codon-AUG. Th
A. Large ribosomal sub unit joins.
es bringing the correct amino acid with it. A pe
s, and the 1st tRNA leaves.
Translation
First a small ribosomal subunit joins mRNA at a start
codon-AUG.
The appropriate tRNA comes to join the mRNA. Large
ribosomal sub unit joins.
Another tRNA comes bringing the correct amino acid
with it. A peptide bond forms between the amino
acids, and the 1st tRNA leaves.
This continues until a stop
codon (UGA, UAG, UAA) is
reached. Then all break apart
and a polypeptide is released.
Mutations
Good, bad, or who cares?
Substitution-redundancy
Deletion or Insertion
Frameshift
Spontaneous
Mutagens
High energy radiation
X rays, UV light
Chemicals
Viruses-DNA or RNA in a
protein coat
RNA viruses-retroviruses
Reverse transcriptase
Lytic cycle
Lysogenic
Viruses of concern
Ebola
Hanta
HIV
Avian (Bird) flu
Influenza 203
AIDS 205
Differentiation
Cancer results from mutations
in genes that control cell
division.
Oncogenes
Proto-oncogenes
Colon Cancer
Recombinant Genetics
Gel Electrophoresis
Separates fragments by their size