11.txt

Tightly. May be modified to counteract environmental changes or gene expression can change to change cell function

Proteins that are expressed all the time

Expressed only when they are needed to be ‘induced’

Transcription

At the promoter, where the transcription is initiated

A ‘decision’ is made about which genes to activate. And transcription factors control whether a gene is active

Regulatory proteins that bind to specific dna sequences near promoter

Negative and positive

a repressor protein preventing transcription

an activator protein binding to stimulate transcription

They inject host cell with nucleic acid that takes over synthesis. New viral particles (virions) appear rapidly and are soon released from the now lysed cell

A typical viral reproductive cycle in a lysogenic phase. The viral genome is incorporated into the host genome and is replicated too

DNA and RNA and may not have a lysogenic phase.

Early stage and Late stage

Promoter in the viral genome binds to host RNA polymerase and the nearby viral genes are ranscribed. Early genes shut down transcription and begin replicating themselves. Posttranscriptional mechanism shuts down host gene. The viral nucleus digests the host’s chromosome.

It takes about 30 minutes, viral genes are now transcribe and they encode the viral capsid proteins and enzymes to lyse the host cell and release new virions

HIV, a virus that encloses itself in the host cell. Fuses with its membrane and through reverse transcriptase, DNA synthesis directs RNA. Two strands of DNA are synthesized and they chill in the host’s chromosome as provirus.

Some can. One such system is transcription terminator. Proteins that interfere with RNA polymerase but HIV counteracts this negative regulation with TAT.

Transactivator of transcription. It allows RNA polymerase to transcribe the viral genome

They only make proteins when needed

Transcription

Adapt quickly to food supply changes. Glucose or lactose may be present

Then glucose is low and E. coli synthesizes all 3 enzymes

The synthesis stops

A compound that induces protein synthesis

Gene expression and regulating enzyme activity

They specify primary protein structure – the amino acid sequence.

They are adjacent on the chromosome, they share a promoter, and they are transcribed together. Their synthesis is ALL OR NONE

It is a gene cluster with a single operon; a short stretch of DNA near the promoter that controls transcription of structural gene. Lac operon encodes for lactose enzymes

It is off unless needed (unless it needs to be induced)

It is on until it needs to be repressed (off)

When B- galactoside predominates in the cell

It detatches and allows RNA polymerase to initiate transcription.

The repressor protein.

The repressible operon is OFF. But it only binds in the presence of a co-repressor

It causes a repressor to change shape in order to bind to the protmoter and inhibit transcription.

It acts as its own repressor in the trp Operon.

Inducible and repressible

A metabolic substrate (inducer) interacts with a regulatory protein (repressor) the repressor then cannot bind and allows for transcription

A metabolic product (co-epressor) binds to regulatory protein which then binds to operator and blocks transcription.

They are turned on when the substrate is available

They are turned on UNTIL the product concentration becomes excessive

Other proteins that bind to RNA polymerase and direct it to specific promoters

Global gene regulation and sporulation

Genes that encode protein relate functions may have different locations but they hav the same promoter sequence- they are on at the same time

This occurs when nutrients are depleted and genes are expressed sequentially, directed by a sigma factor.

Transcription factors. Each promoter contains a core promoter sequence where RNA polymerase binds.

TATA box. Rich in a-t base pairs. Only after general transcription factors bind to the core promoter, RNA polymerase II bind and initiate transcription

DNA sequences that bind activators.

The combination of factors present

Nucear factors of activated t-cells. They are transcription factors and they control genes in the immune system.

Even if the genes are far apart on different chromosomes. They have regulatory sequences that bind the SAME transcription factors.

They use the dehydration response element. A transcription factor changes shape and binds to this element during a drought

Reversal alterations to DNA or chromosomal proteins can be passed on to daughter cells. These epigenetic changes are different from mutations because they are reversible

In cytosine, methyl group is covalently added to 5’ carbon to form 5’-methylcytosine. DNA methyltransferase catalyzes this reaction.

A covatlent one.

When dna replicates, maintenance methylase catalyzes formation of 5’ methylcytosine in new strand and demethylase catalyzes the removal of this extra methyl group

Can bind proteins involved in repression of transcription and genes tent to be silenced (inactive); patterns of DNA methylation can include large regions or whole chromosomes.

Euchromatin and heterochromatin

It is diffuse and light staining; contains DNA and mRNA transcription

It is condensed, dark staining; and containes genes not transcribed

Inactive X chromosome in mammals. The barr body is identifiable during interphase and can be seen in cells of human females.

A mechaninism for epigenetic regulation; it is the lalteration of the chromatin structure.

Histones acetyltransferases change charge by adding acetyl groups and histone loses affinity for DNA. It can activate transcription

Another kind of chromatin remodeling protein that can remove acetyl groups from histones thurs, repressing transcription

Environment; twins can show different methylation after living in different environments.

It can make different mRNAs from the same gene.

Yep! After the initial gene transcript is made.

Small molecules of noncoding RNA. They are important regulators of gene expression

They cause larvae to skip the first step; normally, they would be involved in it

It causes the cell to repeat stage one events.

Protein and mRNA concenrations are not consistently related- they are governed by factors after mRNA is made. They can be blocked or altered as to how long they persist in cell

Inhibition of translation with miRNAs, modification of 5’cap end of mRNA or repressor proteins can block translation (translational repressors).

Creb fam of transcription factors can activate or repress genes by binding to cAMP response element (CRE). It has been linked to addiction and memory tasks as well as metabolism.