8.6 gene expression and regulation

Why is gene expression regulated in prokaryotic cells

It allws them to better respond to stimuli and to conserve energy and materials

When is gene expression regulated in prokaryotic cells

Start of transcription

Effect of bacteria growing in culture medium withoutlactose added

Repressor continues to bind to the operator

Blocks rna polymerase from transcribing the genes

Because it blocks transcription, it is called a repressor protein

Cause of bacteria growing in culture in culture medium with lactose added

Lactose bind to the repressor, which makes repressor change shape and fall of the lac operon

Rna polymerase transcribe the genes in lac operon

Resulting transcript is translated into 3 enzymes

3 enzymes work together to break down lactose

Why do cells in your body differ from each otehr

Different genes are expressed in different cells

What role do transcription factors play in a cell

Bind to dna strand and help rna polymerase know where the gene starts

TATA box

Seven-nucleotide promoter

What is sonic hedgehog an example of

How some genes control the expression of many other genes

Difference between exon and intron

Exons are nucleotide segments that code for parts of the protien

Introns are nucleotide segments that intervene between exons

Promoter

Dna segment that allows a gene to be transcribed

Helps rna polymeerase find where a gene starts

Operon

Region of dna that includes a promoter, an operator and one or more structural genes that code for all the proteins needed to do a specifictask

Lac operon

One of the earliest examples of gene regulation discovered in bacteria

Has three genes which all code for enzymes that play arole in breaking down sugar lactose

What is transcription controlled by in eukaryotic cells

Dna sequences and proteins called transcription factors

Occur in different combinations in different types of cells, results in specialized cells and cell responses

What are regulatory dna sequences recognized by

Transcription factors that bind to the dna strand and help rna polymerase know where gene starts

Some genes control expression of other genes and others play an important role in development

Mrna processing

Mrna produced by transcription is similar to a rough cut of a film that needs editing

Specialized nucleotide is added to the beginning of each mrna molecules which forms a cap, which helps mrna strand to bind to a ribosome and prevent strand from being broken down too fast

End of mrna molecule gets a string of A nucleotides called tail to help mrna exit nucleus

Extra footage is nucleotide segments that are not included in final protein - exons and introns

How does the presence of lactose enable rna polymerase to transcribe lac genes

When lactosee present, it bids to the repressor protein which blocks the repressor from binding to the promoter, which allows rna polymerase to transcribe lac genes and loactose is broken down

What types of dna sequences help eukaryotic cells regulate gene expression

Promoters, enhancers, and silencers

What happens during mrna processing

When the sequences in mrna strand are either expressed in the protein or are cut out