Chapter 1- Cellular Control Flashcards
What does an increase in transcription do?
Produce more mRNA.
What can more mRNA be used for?
Make more proteins.
What are transcription factors?
Proteins that bind to DNA and switch genes on or off by increasing or decreasing the rate of transcription.
What are transcription factors called that increase rate of transcription?
Activators.
What are transcription factors called that decrease rate of transcription?
Repressors.
What does the shape of a transcription factor determine?
Whether it can bind to DNA or not.
What can the shape of transcription factors be altered by?
Binding of certain molecules, e.g sugars and hormones.
Where do transcription factors bind to in Eukaryotes?
They bind to specific DNA sites near the start of their target genes- the genes they control the expression of.
Where do transcription factors bind to in Prokaryotes?
In prokaryotes, the control of gene expression often involves transcription factors binding to operons.
What is an Operon?
A section of DNA that contains a cluster of structural genes, that are transcribed together, as well as control elements and sometimes a regulatory gene.
What are structural genes?
Genes that code for useful proteins such as enzymes.
What are control elements?
promoter (DNA sequence located before structural genes that RNA polymerase binds to) and operator (DNA sequence that transcription factors bind to).
What does regulator gene code for?
activator and repressor.
What is the Lac Operon in E. Coli?
- E. coli respires glucose, but can use lactose if glucose isn’t readily available.
- Genes that produce enzymes needed to respire lactose are found on an operon known as the Lac Opero.
What are the 3 structural genes found on the Lac Operon, and what proteins do they produce to help bacteria to digest lactose?
Lac A- unknown
Lac Z- Beta Galactosidase
Lac Y- Lactose permease
What happens when lactose is not present in the Lac Operon?
The regulatory gene (Lac L) produces the lac repressor, which is a transcription factor that binds to the operator site when there’s no lactose present. This blocks transcription as RNA Polymerase cannot bind to the promoter.
What happens when lactose is present in the Lac Operon?
When lactose is present, it binds to the repressor, changing the repressor’s shape so it can no longer bind to the operator site. RNA Polymerase can now begin the transcription of the structural genes.
How is mRNA edited at a post-transcriptional level?
1) Genes in Eukaryotic DNA contain sections that don’t code for amino acids (introns).
2) During transcription, introns and exons (sections of DNA that do code for amino acids) are both copied into mRNA.
3) mRNA strands containing introns and exons are known as primary mRNA transcripts (pre-mRNA).
4) Introns are removed from pre- mRNA via a process known as splicing- introns removed and exons joined, forming mature mRNA.
5) This takes place in nucleus
6) Mature mRNA leaves nucleus for next stage of protein synthesis- translation.