Analyze how protein synthesis works in terms of:

A.        Transcription of DNA and picture

Transcription is the process of copying the DNA. In a eukaryote, the DNA never leaves the nucleus. The copy is called mRNA. Transcription usually takes place in the cytoplasm of a prokaryote and in the nucleus of a eukaryote. This whole process is performed by an enzyme known as RNA polymerase. In order to make RNA a polymerase must first:

1. Bind to the DNA sequence at a specific sequence (the promoter)
2. Unlink and untangle the two strands of DNA
3. Use one of the DNA strands as a blueprint or guide
4. Match the new nucleotides in the right sequence in the DNA strand (G with C, A with
5. Bind the new RNA nucleotides together to form a copy of the DNA strand (mRNA)

B.     Various types of RNA and picture

The three types of RNA are known as mRNA, tRNA, and the rRNA. The RNA, mRNA, is also known as the messenger RNA. It contains information on the primary sequence of amino acids in a protein to be synthesized. It is the “blueprint” for the protein product. The mRNA carries the code into the cytoplasm where protein synthesis occurs. The anti-codons are used to “read” the mRNA codons. During the life of mRNA, it may be processed, edited and transported prior to translation. Eukaryotic mRNA molecules require extensive processing and prokaryotic mRNA does not. TRNA is known as the transfer RNA. It contains about 75 nucleotides, 3 anti-codons, and one amino acid. The tRNA reads the code and carries the amino acid to be included into the developing protein. There are at least 20 different tRNA’s - one for each amino acid. Part of the tRNA doubles back upon itself to form several double helical sections. The tRNA "reads" the mRNA codon by using its own anti-codon. Each codon is "read" by various tRNA's until the appropriate match of the anti-codon with the codon occurs. Last but not least, rRNA is known as ribosome RNA. In the cytoplasm, ribosome RNA and protein combine to form a nucleoprotein called a ribosome. The ribosome serves as the location and carries the enzymes necessary for protein synthesis. There are about equal parts rRNA and protein. The ribosome attaches itself to mRNA and provides the stabilizing structure to hold all substances in position as the protein is synthesized. Several ribosomes may be attached to a single RNA at any time.

b.       Translation and picture

In the process of translation, the ribosome synthesizes the proteins using the mRNA copy produced in transcription. A tRNA molecule transports amino acids to the ribosome. An anticodon attaches to a codon in the mRNA. A transfer RNA molecule transports other amino acids. A different transfer RNA molecule bonds with the mRNA at the ribosome. These codes must match. Finally a bond is formed between the amino acids. The ribosome then moves along the messenger RNA and exposes a new codon. (PICTURE WITH TRANSCRIPTION!)

C.        How amino acids are supplied

Amino acids are supplied from the food that goes in our mouth and our diet. It is important to eat certain foods which contain a lot of protein because if you don’t eat enough protein, then your body won’t have the efficient amounts of amino acids to perform their duties. High protein foods include meat, poultry, nuts, beans, seeds, etc. At cellular levels, every protein has to be linked to 3 amino acids.  

D.       How amino acids are linked

Amino acids are the basic building blocks of protein. There are 23 total amino acids, but only 20 of them are common. An amino acid links up to another amino acid by a condensation reaction to form a bond that is known as the peptide bond. This process continues until a polypeptide chain is formed.

E.        A codon chart and its function

A codon chart gives the genetic codes and arranges them in a tabular form of the codons for each amino acid in translation of mRNA into protein. It also shows the start and stop codons. The function of the codon chart is to tell the mRNA and tRNA which specific amino acid to get.

-By Kharishma Patel, Deepthy Varghese, Jeswina John, and Miranda Juergens  

8th period, Medical Microbiology, Rickard