6D Gene expression

• the process by which the heritable information in a gene, the sequence of DNA base pairs, is made into a functional gene product, such as protein or RNA

• http://www.youtube.com/watch?v=OEWOZS_JTgk

Gene expression

• Controls & regulates protein synthesis (transcription & translation)

• Remember, every cell is your body contains the exact same DNA…

…so why does a muscle cell have different function and structure than a

nerve cell?

• Because some genes are expressed in a muscle cell that are not expressed in a nerve cell and vice versa.

• Different genes can also be expressed in response to environmental factors or during different stages of an organism’s life cycle.

Gene expression

• Its like a light switch… certain traits are “turned on” & “turned off”

Gene

• Segment of DNA that codes for a trait• Ex: hair color, eye color

Intron

• any nucleotide sequence within a gene that is removed by RNA splicing while the final mature RNA product of a gene is being generated

Exon

• nucleotide sequence encoded by a gene that remains present within the final mature RNA product of that gene after introns have been removed by RNA splicing.

• This is the expressed genetic material… the light is turned on.

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=SLfA8_a12VOmoM&tbnid=NWD5081oLXctrM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww2.estrellamountain.edu%2Ffaculty%2Ffarabee%2FBIOBK%2Fbiobookgenctrl.html&ei=4Y9pUpGsFKKGyQHYlIHIBw&bvm=bv.55123115,d.aWc&psig=AFQjCNE4nzBcwFmdiD9Y8aYb_8N1dqIyWA&ust=1382736202188646

Gene Expression in Prokaryotic Cells

• Prokaryotic cells such as…

BACTERIA

… contain operons.

Operon

• Groups of genes that are regulated together.

• “Buddy system”• Located next to 2 regulatory regions

of DNA – promoter and operator

Promoter• a region of DNA that initiates transcription of

a particular gene• promoters are located near the genes they

transcribe

Operator• a gene that activates the production of

messenger RNA by adjacent structural genes

• When RNA polymerase binds to the promoter, it is a signal that shows RNA polymerase where to begin transcription. The operator is adjacent to the promoter and it controls the rate of transcription.

Repressor

• A protein called a repressor can bind to the operator. If the repressor binds to the operator, the RNA polymerase cannot access the operon and transcription does not occur.

lac operon

lac operon

• The group do 3 genes (lac Z, lac Y, lacA) MUST be turned on before the bacterium can use lactose as food.

• When lactose is not present in the bacterium’s environment, the repressor binds to the operator.

• The protein blocks the movement of RNA polymerase along the DNA, and the operon is not transcribed into RNA.

• When lactose is present, the repressor binds to lactose instead opt to the operator. The path of DNA is cleared from transcription to occur (like a gate across a road).

Gene Expression in Eukaryotic Cells

• Genes are rarely found in clusters that are activated by the same promoter. Many eukaryotic genes are preceded by a short region of DNA called the TATA box.

Gene Expression in Eukaryotic Cells

TATA box

• Positions RNA polymerase.

Transcription Factors

• DNA-binding proteins that aid in regulating gene expression.

• Many types of transcription factors. Each type affects gene expression in different ways.

• Ex: opening tightly packed chromatin (enhancing transcription)

•Ex: opening tightly packed chromatin (enhancing transcription)

Types of Transcription Factors

• opening tightly packed chromatin (enhancing transcription)

• Attracting RNA polymerase• Blocking access to certain genes

• http://www.youtube.com/watch?v=T9Wszg7FhxE

http://www.youtube.com/watch?v=2sMFswbOgKk

http://phet.colorado.edu/en/simulation/gene-expression-basics

http://phet.colorado.edu/en/simulation/gene-machine-lac-operon