structure and function of dna. structure of dna(deoxyribonucleic acid) discovered by watson &...
TRANSCRIPT
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 types1. Adenine- A2. Guanine-G3. Cytosine- C4. 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
Hydrogen bonds
Nucleotide
Sugar-phosphate backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Structure of DNA
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
A G C T A C G C A one side T C G A T G C G T 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
Figure 12–11 DNA ReplicationSection 12-2
Go to Section:
Growth
Growth
Replication fork
DNA polymerase
New strand
Original strand DNA
polymerase
Nitrogenous bases
Replication fork
Original strand
New strand
Warmup- Transcribe the DNA and translate the codon sequence into a protein.
DNA mRNA tRNA Amino acid
GCC CGG GCC
AAA UUU AAA
CGC GCG CGC
GCG CGC GCG
TTT AAA UUU
ATT UAA AUU