Describe: gene control b.stev

BACTERIA: control which genes are expressed according to their requirements: enzymes needed for chemical processes proteins for renewal of cellular structures defence monitoring of the environment use of different components for replication digestive requirements for the environment control of timing and evolutionary change TWO TYPES: Positive control Negative control (Wikipedia, 2008)

enzymes needed for chemical processes

proteins for renewal of cellular structures

defence monitoring of the environment

use of different components for replication

digestive requirements for the environment

control of timing and evolutionary change

TWO TYPES:

Positive control

Negative control

bacteria need to make specific enzymes to utilise lactose as a nutrient lactose binds to the repressor protein & prevents it from attaching to the DNA, thus allowing transcription to occur POSITIVE CONTROL: repressor protein attachment to the operator is prevented via chemical interaction: ie: presence of lactose (sugar) in the environment (Campbell N. A, Reece J. B, 2005)

when the REPRESSOR PROTEIN binds to the OPERATOR it prevents transcription regulatory gene operator structural genes promoter TRANSCRIPTION FACTOR OPERON RNA polymerase direction of transcription = lactose binds , allows transcription to occur

prevents RNA polymerase movement over the DNA strand’s structural genes that hold certain sequences for the protein(s) to be made NEGATIVE CONTROL: prevents the process of transcription repressor protein is made that attaches to the operator on the transcription factor ie: tryptophan (amino acid), bacteria produce this though when enough has been made: regulatory gene produces the repressor protein that attaches without hindrance to the operator

prevents the process of transcription

the REPRESSOR PROTEIN binds to OPERATOR & prevents transcription regulatory gene operator structural genes promoter TRANSCRIPTION FACTOR (1) OPERON RNA polymerase direction of transcription

RNA polymerase can not move over the DNA strand: prevents transcription regulatory gene operator structural genes promoter TRANSCRIPTION FACTOR (2) - negative control RNA polymerase direction of transcription

Bibliography Campbell N. A, Reece J. B. (2005). Biology (7th ed.) . San Francisco: Benjamin Cummings Pommerville J.C. (2004). Alcamo’s – Fundamentals of Microbiology (7 th ed.). Massachusetts: Jones and Bartlett. Wikipedia. (2008). Gene expression – wikipedia, the free encyclopedia . Retrieved October 23, 2008, from http:www. en.wikipedia. org/wiki/ Gene _ expression - 49k -