Wednesday, February 14, 2007

AUG are always the start codons. Each codon is one amino acid and is made up of three bases.
There are 20 amino acids, but there are multiple condons for each amino acid.


What is it?
DNA translation converts the mRNA sequence into amino acids that form protiens. This creates most of the protiens that make up cells. It creates the last step from DNA to a protien.
Wher does it occur?
Translation occurs outside the nucleas also known as in the cytoplasm. Eventhough this is true one article suggests that translation can occur inside the nucleas. Click here to see.
When does it occur?
Translation occurs right after transcription is done and the mRNA is transported out of the nucleas.
How does it Happen?
During DNA translation, messenger RNA, transfer RNA, and ribosomes work together to produce proteins. A ribosomal subunit attaches to a mRNA molecule. The Transfer-RNA transports the amino acid from the cytoplasm to the ribosome. The start codon attaches to Met this starts making the protein.

What is it?
The DNA Transcription is the process of building RNA copy of a DNA sequence.
Where does it occur?
It occurs in the nucleus of the cell.
When does it happen?
It occurs after DNA replication.
How does it happen?
1. The gene sequence is copied into messenger RNA (mRNA)
- The mRNA is single stranded and has 4 nucleotide like DNA, but instead of Thymine (T) it has Uracil (U).
- Transcription continues until one entire gene has been converted to RNA.
2. After Transcription the whole mRNA strand is transported out of the nucleus to the cytoplasm.
3. In the cytoplasm, the mRNA strand is translated into an amino acid.

Tuesday, February 13, 2007

DNA Replication

What is it?
DNA Replication is a process used to copy chromosomes inside the nucleas of a cell before the cell divides.
Where does it occur?
This process occurs inside the cell's nucleas.
When does it Happen?
The Replication of DNA occurs when before the cell can divide.
How Does it Happen?
1.DNA Replication begins with one double strand of DNA.
2.The Double strand helix is partially unwound by SSB Protiens and helicases into what is known as a replication fork.
3.As the two DNA strands unzip the run in anti-parallel directions.
4. DNA polymerase moves into position at the point where synthesis will begin. But since the Polymerase can only move from 5' to 3' direction the strands will replicate differently.
5.In the leading strand the Primase lays down the RNA primer.
6.Now the the RNA primer had been laid down Polymerase III builds a second strand in the same direction that the double helix is being opened.
7. In the remaining gaps more RNA primers attach yeilding Okazki Fragments (lagging strands)
8. RNA Primer stripped away DNA polymerase replaces with DNA nucleotides.
9. Ligase "glues" the remaining gaps in the sugar-phosphate backbone.

click to enlarge


This project was created to share information on DNA Replication, Transcription and Translation. Our posts will answer many general questions about the three different topics. To view the guidlines of the project click here.