Transcript DNA, RNA, and Protein Synthesis

DNA, RNA,
and Protein Synthesis
Chapter 10
DNA Double Helix
• 1953 – James Watson
and Francis Crick
came up with the
model of DNA
LE 16-6
Rosalind Franklin
Franklin’s X-ray diffraction
photograph of DNA
DNA
• DNA – Deoxyribonucleic acid
• Stores and transmits genetic information
that tells cells which proteins to make and
when to make them.
• Proteins, in turn, form the structural units of
cells and help control chemical processes
within cells.
What is DNA?
• DNA is a long
molecule or “chain”
of nucleotides.
• A nucleotide is
made up of 3 things:
phosphate group,
deoxyribose, and a
nitrogen base.
DNA Structure
• Made of repeating
subunits called
nucleotides.
• There are 4 kinds of
nitrogen bases.
DNA Structure
• Four nitrogen bases
–
–
–
–
Adenine,
Thymine
Guanine
Cytosine
Double-stranded
Double Helix
Charagaff’s Rule
Adenine = Thymine
Guanine = Cytosine
DNA Structure
Pyrimidines
• 1 ring base
– Thymine and Cytosine
Purines –
• 2 ring base
– Adenine and Guanine
DNA REPLICATION
DNA Replication
• DNA replication is the process by which
DNA is copied in a cell before the cell
divides by mitosis, meiosis, or binary
fission.
DNA Replication
• When DNA is
copied, the 2
strands “unzip”
• DNA Helicase
enzyme acts as the
“unzipper”
Steps of DNA replication
• Helicase enzymes separate DNA’s two chains of
nucleotides
Steps of DNA replication
• Enzymes called DNA polymerases bind to
the separated chains. One nucleotide at a
time, the enzyme constructs a new
complementary chain of nucleotides
3’ to 5’
Steps of DNA replication
• DNA polymerases finish replicating the
DNA and fall off. There are now two
identical DNA molecules
DNA: Base Pairing
• Each nucleotide in DNA preferentially
pairs with its partner nucleotide on the
opposite strand. So one side
• A pairs with T
“compliments” the other.
• C pairs with G
• This structure of DNA is the physical
basis for inheritance.
DNA Replication
Use the principle of base pairing to create
this strand of DNA’s complimentary copy.
ACC GCT TTA GCC GAT TAC GAA
That’s easy!!
TGG
When you’re done with that example, create a
new DNA strand for your partner to work on.