Describe: bacterial gene

b.stev

Transcriptional Promoter Initiation Codon Operator Operons Open Reading Frame Ribosome Binding Site Start/ Stop Codon Transcription Terminator

BACTERIAL GENE components to be outlined in the description:

- easily utilise glucose as a nutrient- an example of when transcription is used

IF: lactose is present & there is insufficient glucose for required needs the bacteria must produce specific enzymes so that the sugar lactose can be utilised in a metabolic pathway: enzymes

o B galactosidaseo Permeaseo Galactose acetylase

the presence of lactose causes the repressor protein NOT to bind to the transcription unit - signalling the process to begin

ABOUT BACTERIA:

(Campbell N. A, Reece J. B, 2004)

Open Reading Frame: sequence whereby NO stop codons are

present thus, the sequence represents a particular function. The

sequence(s) vary in length in accord to their particular function they

perform.

THE particular codon sequence that initiates the point upon the

transcription factor where the process begins is the amino acid:

Methionine – AUG (start codon)

this is an example of one of the 64 different amino acids that

surmount to the,”dictionary of the genetic code.”

AND, when the required sequence is read there are:

3 codons that initiate the process to cease

UAA/ UAG/ UGA – known only as stop codon(s)

when the REPRESSOR PROTEIN binds

to

the OPERATOR it prevents

transcription

regulatory gene

operator

structural genes

promoter

TRANSCRIPTION FACTOR

OPERON

RNA polymerase

direction oftranscription

regulatory gene

operator

structural genes

promoter

a RIBBON of codons is made- named: the mRNA transcript- when completed it detaches

RNA polymerase

direction oftranscription

TO commence transcription : a promoter attracts

RNA polymerase to bind specifically in place to it

PROMOTER: sequence in DNA - RNA polymerase recognises then binds in position to the

start point; extends several dozen nucleotide pairs

upstream

ALSO:

promoter determines which of the 2 strands of DNA helix

is going to be used as the template strand in

transcription(Campbell N. A, Reece J. B, 2004)

OPERONS: structural genesclusters of genetic codes that provide the: codons for

proteins to be made for metabolic function to nutrients

OPERATOR: before operon sequence of codons:

codons that consist of the operator are placed

to determine if TRANSCRIPTION is to take place

repessor protein can attach to this

pointpoint to prevent the transcription

TRANSCRIPTION TERMINATOR: a stop codon is read in

the sequence that causes the mRNA transcript to release

and RNA polymerase detaches from the DNA transcript

THE made mRNA transcript floats within the cytoplasm of the bacterium until it encounters a ribosome

RIBOSOME: makes the useable proteins for the bacteriaconsists:consists: two parts

WHEN complete it pauses, breaks off the protein & moves to the next start codon to create the next protein needed

Large: consists of 49 proteinsSmall: consists of 33 proteins

(Pommerville J.C, 2004)

APE

large ribosome

mRNA transcript

small ribosome

bind site:

upstream to the start codon is a specific

sequence

that the small ribosome recognises and

binds to, so

follows the large ribosome that attaches

above this

5’3’

RIBOSOME bind sites

E: exit siteP: peptidyl-tRNA siteA: aminoacyl-tRNA site

direction of translation

Bibliography

Campbell N. A, Reece J. B. (2005). Biology (7th ed.). San Francisco: Benjamin Cummings

Pommerville J.C. (2004). Alcamo’s – Fundamentals of Microbiology (7th ed.). Massachusetts: Jones and Bartlett.