Gene Polyribosome

Figure 46-1. Diagrammatic representation of the two branches of protein sorting occurring by synthesis on (1) cytosolic and (2) membrane-bound polyribosomes. The mitochondrial proteins listed are encoded by nuclear genes. Some of the signals used in further sorting of these proteins are listed in Table 46-4. (ER, endoplasmic reticulum GA, Golgi apparatus.)...

In addition, several ribosomes can independently and simultaneously translate a mRNA molecule and, hence, synthesize several identical polypeptide chains concurrently (Figure 12.3). Such clusters or groups of ribosomes are called polyribosomes or polysomes. The number of attached ribosomes depends on the size of the mRNA and how frequently ribosomes can initiate at the start of a gene sequence. Because RNA transcription and translation are neither temporally nor spatially separated in prokaryotes, it is possible for translation to begin before transcription is completed. However, we have already noted that prokaryotic mRNAs have short half-lives this is probably a result of their continuous degra-... 

The linear deoxyribonucleotide sequence information encoded in genes is copied into a linear sequence of ribonncleotides in messenger RNA (mRNA) by the process of transcription. Ribosomes bind one at a time near to the 5 end of each mRNA molecule and translate the ribonucleotide base sequence into an aminoacyl sequence according to the genetic code. Each mRNA is bound to more than one ribosome at a time, forming a polyribosome, often abbreviated to polysome. Typically the rate of... 

Aminolevulinic acid (ALA ) formation is catalyzed by mitochondrial ALA synthase, which condenses glycine and succinyl-CoA to ALA. The enzyme is located on the matrix side of the inner mitochondrial membrane. It is encoded by a nuclear gene and is synthesized in the cytosol on the free polyribosomes as a... 

How would a mutation in the poly (A)-binding protein I gene affect translation How would an electron micrograph of polyribosomes from such a mutant differ from the normal pattern ... 

Dramatic advances in molecular biology have elucidated the manner in which genes control the function of an organism. The gene is a template of DNA which transmits its information to another template of RNA die RNA carries its information to the polyribosomes where it is translated into a sequence of amino acids. This template mechanism of information transfer permits an accurate and essentially error-free control of protein... 

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