Transcript DNA - Harrison High School

Structure and Function of
DNA
Structure of DNA(deoxyribonucleic acid)
• Discovered by Watson
& Crick in 1953
• DNA is a nucleic acid
• DNA is made up of
small subunits called
nucleotides
The nucleotides are made up of:
•deoxyribose(sugar)
•phosphate group
• nitrogen bases-4 types
1. Adenine- A
2. Guanine-G
3. Cytosine- C
4. Thymine-T
DNA is actually 2
long chains of
nucleotides that
are joined together
in the form of a
ladder. The ladder
is twisted in the
form of a double
helix or spiral
Structure of DNA
Nucleotide
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
The sides of the
ladder are
composed if
alternating
deoxyribose(sugar)
and phosphate. The
rungs of the ladder
are composed of
pairs of nitrogen
bases.
The nitrogen bases always pair up in a
specific pattern.
•Adenine(A) pairs up with Thymine(T)
•Guanine(G) pairs up with Cytosine(C)
Example
AGC
TCG
TAC
ATG
GCA
one side
CGT
other side
All organisms have the same type of
nucleotides. The nucleotide arrangement
provides for all the different types
Ex- A mouse and a rosebush have the same
nucleotides. However, they are different
because their nucleotides are in different
orders.
*This sequence of nucleotides forms the
genetic information(code) of an organism.
Replication of DNA
Before meiosis and mitosis (during
Interphase) a copy of DNA must be made so
that when the new cells are formed, they
each get an exact copy of the genetic
information.
This DNA copy is made through a process
known as replication.
Steps of Replication
During replication, each strand serves as a
pattern or TEMPLATE to make new DNA
molecule.
• First step: DNA (H bonds are broken)
unzips into 2 strands
• Second step: free nucleotides join onto
“unzipped” strands to form 2 new strands
of DNA
• 2 complete strands will result, these will be
exactly alike
Section 12-2
Figure 12–11 DNA Replication
New strand
Original
strand
DNA
polymerase
Growth
DNA
polymerase
Growth
Replication
fork
Replication
fork
New strand
Go to
Section:
Original
strand
Nitrogenous
bases
Warmup- Transcribe the DNA and translate
the codon sequence into a protein.
DNA
mRNA
tRNA
GCC
AAA
CGC
GCG
TTT
ATT
CGG
UUU
GCG
CGC
AAA
UAA
GCC
AAA
CGC
GCG
UUU
AUU
Amino acid