What determines sequence/order of amino acids in the polypeptide or protein
There are 4 bases → A C G T → in DNA molecule
→ 3 Bases together make up a Codon
→ Each codon codes for one acid
Suppose DNA strand that determines production of polypeptide or protein has following sequence of codons → CGG CCA CAA TTT → sequence of amino acids in the protein will be: Arginine - Proline - Glutamine - Phenylalanine
However if sequence of Codons is CCA CGG TTT CAA Sequence of amino acids will be: Proline - Arginine - Phenylalanine - Glutamine
Hence showing how sequence of Bases in the DNA determines the sequence of amino acids in a polypeptide*** KEY POINT
- cell cannot directly use the DNA template to make protein
- protein synthesis is a 2 step process (Transcription and Translation)
- Transcription takes place in the nucleus while translation takes place in cytoplasm
Steps(From Above Image)
- In the nucleus, the message in the gene is copied into an mRNA (messenger RNA)
- mRNA travels to cytoplasm and attaches to a ribosome
- As the ribosome moves along the mRNA, it synthesises a polypeptide
- When the ribosome leaves the mRNA, the polypeptide is released
→ Note: message in gene is used to make an mRNA → so it is copied INTO an mRNA.
Sample
for the synthesis of a protein- you NEED to write: XXX gene codes for sequence of amino acids in XXX protein CHECK WITH ASNWER KEY WA2 LATER