Microbiology Demystified

Once the transcription process is completed, information of the mRNA is

turned into protein in the translation process. The translation processis one

in which genetic information encoded in mRNA is translated into a specific

sequence of amino acids that produce proteins.

Appropriate amino acids are brought to the translation site in the ribosomes

and are assembled into a growing chain. It is here that tRNA recognizes specific

codons. Each tRNA molecule has an anticodon, which is a sequence of three

bases that is complementary to the bases on the codon. These bases are then

paired, and amino acids are brought to the chain.

This process continues until a polypeptide is produced. The polypeptide is

removed from the ribosome for further processing. The polypeptide may be

stored in the Golgi body of a eukaryotic organism. The mRNA molecule degen-

erates and the nucleotides are returned to the nucleus. The tRNA molecule is

returned to the cytoplasm and combines with new molecules of amino acids.

GENOTYPE AND PHENOTYPE: REALIZING

YOUR POTENTIAL

The genetic makeup of an organism is called a genotypeand represents that

organism’s potential properties. Some properties may not have developed. Those

that do develop are called an organism’s phenotype. The phenotyperepresents

expressed properties, such as blue eyes and curly hair.

A genotype is the organism’s DNA (a collection of genes). The phenotype is

a collection of proteins. The majority of the cell’s properties comes from the

structures and functional properties of these proteins.

Controlling Genes: You’re Under My Spell

The process of making proteins (remember, polypeptides become proteins either

after they are combined with other polypeptides or when they become biologi-

cally functional) begins with the copying of the genetic information found in

DNA, into a complimentary strand of RNA. This copying is called transcription.

Messenger RNA (mRNA) will carry the coded information or instructions for

assembling the polypeptides from DNA to the ribosomes of the cell’s endoplas-

mic reticulum where the polypeptides will be made.

(^124) CHAPTER 7 Microbial Genetics