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Flashcards in Chapter 11 Deck (48):
1

Constitutive Genes

Actively expressed all the time

2

Inducible Genes

Expressed only when their proteins are needed by the cell.

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Selective Gene transcription

The cell has control over when it wants specific genes to be expressed.

4

Transcription factors

Control whether or not a gene is active

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Repressor

(Negative regulation) Binds near the promoter to prevent transcription.

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Activator

(Positive regulation) Binds near promoter to stimulate transcription.

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Virus

Injects its genetic material into a host cell, and often turns that cell into a virus factory.

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Lytic life cycle

The host cell immediately begins producing new viral particles after being infected

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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.

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HIV (Human Immunodeficiency virus

Infective agent that causes Aquired immunodeficiency syndrome (AIDS) in humans

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Retrovirus

virus whose genome is a single stranded RNA

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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.

13

Number of proteins involved in the uptake of lactase by E. Coli

3 proteins

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Inducer

switches on expression in inducible genes

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structural genes

The genes that encode the three enzymes for processing lactose in E. Coli

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Operon

cluster of genes with a single promoter

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operator

in lac operon, is near the promoter and controls transcription of the structural genes.

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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

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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.

20

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

21

Summary of Repressible systems

The product of a metabolic pathway (corepressor) binds to the repressor protein which then binds to the operator, blocking transcription.

22

Sigma Factors

Special proteins in prokaryotes called Sigma factors that can bind to RNA polymerase and direct the polymerase to specific promoters.

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TATA Box

The most common core promoter. Rich in A-T base pairs.

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RNA Polymerase II

The polymerase that transcribes the protein-coding genes in eukaryotes,

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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.

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Enhancers

DNA sequences that bind activators to initiate translation.

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Silencers

DNA sequences that bind repressors to restrict translation.

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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.

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Epigenetic changes

Regulating transcription of DNA by reversible, non sequence specific alterations to the DNA in the nucleus. These are heritable alterations.

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DNA Methylation

Chemically modifying cytosine in DNA that use repressors, inactivating the DNA.

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DNA Methyltransferase

The enzyme that catalyzes the covalent addition of the methyl group to cytosine.

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CpG Islands

DNA regions rich in C and G residue doublets

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Maintenance methylase

When DNA is replicated, this catalyzes the formation of 5-methylcytosoine in the new DNA strand, because it is heritable.

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Demethylase

Catalyzes the removal of the methyl group from cytosine.

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Euchromatin

Uncondensed transcribable DNA. Unmethalated.

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Heterochromatin

Condensed untranscribable DNA. Methylated.

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How is DNA methylation involved in the X chromosomes in females

One of the X chromosomes is heterochromatin, and so cannot be transcribed

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Chromatin remodeling

Large amounts of DNA are packed within the nucleus with histones

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Histones

The proteins that wind around the DNA, tightening it, and repressing it, not allowing it to transcribe.

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Histone acetyltransferases

Can add acetyl groups to the histones to neutralize charges and loosening the DNA and allowing it to transcribe. It activates transcription.

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Histone deacetylase

Can remove the acetyl groups from histones and repress transcription.

42

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.

43

Alternative splicing

Can be a deliberate mechanism for removing introns and splicing them together in different ways, often removing exons as well.

44

MicroRNA (miRna)

tiny rnA molecules that can inhibit and degrate mRNA.

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How can translation of mRNA be regulated?

By inhibiting translation with miRNAS, modifying the 5' cap, and translational repressor proteins

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translational repressor proteins

proteins that block translation by binding to mRNAs and preventing their attachment to the ribosome.

47

Ubiquitin

a 76-amino acid involved in the destruction of proteins

48

Proteosome

a huge protein complex that targets proteins to be destroyed.