Chapter 11 Flashcards
Constitutive Genes
Actively expressed all the time
Inducible Genes
Expressed only when their proteins are needed by the cell.
Selective Gene transcription
The cell has control over when it wants specific genes to be expressed.
Transcription factors
Control whether or not a gene is active
Repressor
(Negative regulation) Binds near the promoter to prevent transcription.
Activator
(Positive regulation) Binds near promoter to stimulate transcription.
Virus
Injects its genetic material into a host cell, and often turns that cell into a virus factory.
Lytic life cycle
The host cell immediately begins producing new viral particles after being infected
Lysogenic phase
Dormant phase found in some life cycles. The viral genome becomes incorporated into host cell. Replicated along with the host genome. Later triggered by environmental signal to start virus production.
HIV (Human Immunodeficiency virus
Infective agent that causes Aquired immunodeficiency syndrome (AIDS) in humans
Retrovirus
virus whose genome is a single stranded RNA
reverse transcriptase
After infection, this makes a DNA strand that is complementary to the HIV RNA while also degrading it and making a second DNA.
Number of proteins involved in the uptake of lactase by E. Coli
3 proteins
Inducer
switches on expression in inducible genes
structural genes
The genes that encode the three enzymes for processing lactose in E. Coli
Operon
cluster of genes with a single promoter
operator
in lac operon, is near the promoter and controls transcription of the structural genes.
lac Operon
The lac operon is not transcribed unless latose (or other B galactoside) is the predominant sugar. This rmoves the repressor normally bound to the operator
trp operon
Typ operon is switched off when its repressor is bound to the operator. In this case, the repressor beinds to the DNA only in the presence of a corepressor. Tryptophan functions as the corepressor in this case.
Summary of inducible systems
the substrate of metabolic pathway (inducer) interacts with a transcription factor (The repressor), releasing the repressor from the operator, allowing transcription
Summary of Repressible systems
The product of a metabolic pathway (corepressor) binds to the repressor protein which then binds to the operator, blocking transcription.
Sigma Factors
Special proteins in prokaryotes called Sigma factors that can bind to RNA polymerase and direct the polymerase to specific promoters.
TATA Box
The most common core promoter. Rich in A-T base pairs.
RNA Polymerase II
The polymerase that transcribes the protein-coding genes in eukaryotes,
General Transcription Factors
Certain factors must bind to the promotor before the RNA Polymerase II. First TFIID binds to TATA box, followed by Polymerase and other transcription factors.
Enhancers
DNA sequences that bind activators to initiate translation.
Silencers
DNA sequences that bind repressors to restrict translation.
How do Enhancers and Silencers work?
After repressors or activators bind to the enhancers and silencers, they cause the DNA to bend. This bending along with other transcription factors, determines the initiation of transcription.
Epigenetic changes
Regulating transcription of DNA by reversible, non sequence specific alterations to the DNA in the nucleus. These are heritable alterations.
DNA Methylation
Chemically modifying cytosine in DNA that use repressors, inactivating the DNA.
DNA Methyltransferase
The enzyme that catalyzes the covalent addition of the methyl group to cytosine.
CpG Islands
DNA regions rich in C and G residue doublets
Maintenance methylase
When DNA is replicated, this catalyzes the formation of 5-methylcytosoine in the new DNA strand, because it is heritable.
Demethylase
Catalyzes the removal of the methyl group from cytosine.
Euchromatin
Uncondensed transcribable DNA. Unmethalated.
Heterochromatin
Condensed untranscribable DNA. Methylated.
How is DNA methylation involved in the X chromosomes in females
One of the X chromosomes is heterochromatin, and so cannot be transcribed
Chromatin remodeling
Large amounts of DNA are packed within the nucleus with histones
Histones
The proteins that wind around the DNA, tightening it, and repressing it, not allowing it to transcribe.
Histone acetyltransferases
Can add acetyl groups to the histones to neutralize charges and loosening the DNA and allowing it to transcribe. It activates transcription.
Histone deacetylase
Can remove the acetyl groups from histones and repress transcription.
How can epigenetic changes be induced by the environment?
Health, toxins, and the settings humans can affect their DNA, slightly altering it. This is way twins differ as they age.
Alternative splicing
Can be a deliberate mechanism for removing introns and splicing them together in different ways, often removing exons as well.
MicroRNA (miRna)
tiny rnA molecules that can inhibit and degrate mRNA.
How can translation of mRNA be regulated?
By inhibiting translation with miRNAS, modifying the 5’ cap, and translational repressor proteins
translational repressor proteins
proteins that block translation by binding to mRNAs and preventing their attachment to the ribosome.
Ubiquitin
a 76-amino acid involved in the destruction of proteins
Proteosome
a huge protein complex that targets proteins to be destroyed.
