Uncovering the Relationship Between Genes and Proteins - ATA Scientific
Gene expression is the process by which information from a gene is used and finally protein synthesis by means of translation of the mature. Ever wondered the relationship between genes and proteins? Discover this and the tools used to confirm this relationship here. Gene Expression and Protein Synthesis . in the DNA template strand, and the enzyme will catalyze formation of a phosphodiester bond between them.
Proteins are chains of chemical building blocks called amino acids.
A protein may contain a few amino acids or it could have several thousands. The size of a protein is an important physical characteristic that provides useful information including changes in conformation, aggregation state and denaturation. Protein scientists often use particle size analysers in their studies to discuss protein size or molecular weight.
- Fig. 3.1.1
- Unit 1: The Relationship between Genes and Proteins
Archibald Garrod Archibald Garrod was one of the first scientists to propose that genes controlled the function of proteins. Inhe published his observations regarding patients whose urine turned black. This condition known as alkaptonuria happens when there is a buildup of the chemical homogentisate, which causes the darkening of urine.
In most situations, excess amounts of amino acid phenylalanine are metabolised by the body. This led Garrod to surmise that the enzyme responsible for its breakdown must be defective in these patients.
In addition, since the black urine phenotype was passed from generation to generation in a regular pattern, Garrod reasoned that a gene had to be responsible for the production of the defective enzyme. He attributed a defective enzyme to a defective gene, suggesting a direct link between genes and proteins.
The Relationship Between Genes and Proteins Most genes contain the information require to make proteins. Events at initiation of transcription a. The initiating nucleotides can bind to the enzyme, as directed by their complementary nucleotides in the DNA template strand, and the enzyme will catalyze formation of a phosphodiester bond between them.
During abortive initiation, the polymerase catalyzes synthesis of short transcripts about 6 or so nucleotides long and then releases them. This binding is associated with "resetting" the catalytic center so that the enzyme will now catalyze the synthesis of oligonucleotides long. The enzyme now translocates to an new position on the template. During this process sigma leaves the complex.
A conformational change in the enzyme associated with sigma leaving the complex lets the "thumb" wrap around the DNA template, locking in processivity. Thus the core enzyme catalyzes RNA synthesis during elongation, which continues until "signals" are encountered which indicate termination.
Events at initiation 3. Initiation RNA polymerase holoenzyme binds at the promoter, unwinds DNA open complex and form phosphodiester links between the initiating nucleotides.
Elongation s dissociates and core elongates.
Perhaps other factors bind to enhance the processivity maybe NusA? The factor r is required at many terminators. Sites on RNA Polymerase core a.
The enzyme covers about 60 bp of DNA, with a transcription bubble of about 17 bp unwound. The duplex DNA being transcribed is unwound at one active site on the enzyme, thereby separating the two strands Fig.
Part Three: Gene Expression and Protein Synthesis
The two strands are rewound at another active site, regenerating duplex DNA. The incoming nucleotide is linked to the growing RNA chain by nucleophilic attack of the 3' OH on the a phosphoryl of the NTP, with liberation of pyrophosphate.
The reaction progresses the enzyme moves about 50 nts per sec. This is much slower than the rate of replication about nts per sec.
This effect of the increase in W will be exerted in the DNA ahead of the polymerase. T will increase by 1 for every 10 bp rewound.