REPLICATION

 

DNA must be able to copy itself. The process of making a copy of itself is called replication.  To make a copy, you need an original AKA a template.  Because DNA is a double helix if has templates built into it.  There are steps to the replication process.

In order for DNA to go through replication it must first unwind.

 

Step 1: an enzyme unwinds the twisted double helix

 

Step 2: an enzyme unzips the untwisted double helix, breaking the bonds between the bases.

As the bonds break, each strand of the DNA molecule becomes separate.  Free floating bases float around the cell. Specific enzymes match up these free floating bases with the template.  A pairs up with T, T pairs up with A, C pairs up with G and G pairs up with C.

 

Step 3: one by one, new bases are joined together to make a new strand opposite each old strand.  When replication is complete, 2 double stranded DNA molecules are formed.  They are identical to the original.

 

TRANSCRIPTION

 

A scribe is a person who writes down important information.  In the process of transcription, DNA acts like a scribe.  Transcription is the copying of a genetic message from a strand of DNA into a molecule of RNA.  DNA writes a message to RNA so RNA can tell the ribosomes to make proteins.  The RNA that is created is called messenger RNA (mRNA). 

 

----------------------------------

    A G T C G T A A G C T G       DNA

 

       U C A G C A U U C G T C       mRNA

 -----------------------------------

U= Uracil

 

RNA is only a single strand!!

 

The bases are the message that the messenger RNA carries to the ribosomes to tell them to make proteins.  RNA is the instructions on how to make a protein. 

 

 

TRANSLATION

 

1) What is a ribosome and what does it do?

A ribosome is an organelle within the cell that makes proteins.

 

 

2) How does the ribosome make proteins?

It needs amino acids to make proteins

 

3) How do you get an amino acid?

DNA codes for the amino acid sequence.  DNA provides RNA with the instruction for making proteins.

--------------------------------------- RNA

              A U G  C C A  C G A  U G A

 

Triplets of 3 bases are called a codon.  Each codon represents a specific amino acid.

 

--------------------------------------- RNA

              A U G   C C A   C G A     U G A

 

The ribosome translates RNA language into amino acid language to make a protein.  Ribosomes make proteins by translating the mRNA into proteins.

 

Website with the table of  codons:

http://student.ccbcmd.edu/biotutorials/protsyn/fg9.html