Genetics chapter 14 & 15

The lac operon has how many operator sites for the lac repressor

3 O1 Next to the promoter O2 Downstream in the lacZ coding region O3 Slightly upstream of the CAP site

An operon is flaked by

A promoter and a terminator, two or more structural genes are found between these sequences

catabolic repression

A type of positive transcriptional control in which the end product of a catabolic pathway inhibits further transcription of the gene encoding an enzyme early in the pathway.

92. Antisense RNA

A way to regulate translation. This is an RNA strand that is complementary to a strand of mRNA. It is used in osmoregulation which regulates the amount of H2O in a cell

allolactose

Acts as a small effector molecule to regulate the lac operon

ARS's

Autonomously Replicating Sequences - replicating sequences that are found in eukaryotic cells. There are multiple ARSs through out the chromosome. Contain a AT rich region Contain a copy of the ARS consensus sequence

Inhibitor

Binds to an activator protein and prevents it from binding to the DNA

Inducible genes

Genes whose expression is turned on by the presence of some substance. Regulate catabolic pathways.

negative control mechanism of the lac operon

It involves the lac repressor protein The inducer is allolactose which binds to the lac repressor and inactivates it

In the lac operon the repressor binds to the __________

Operator

What are the 2 types of regulators

Repressor Activator

Allosteric regulation

The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site. the action of small effector molecules like allolactose, A product of beta galactosidase, when lactose is present in a cell and glucose is absent beta G converts some of the lactose to allolactose which binds to the lac repressor and in doing so the lac operon is activated.

autopolyploidy

The state of having more than two full sets of chromosomes due to a mutation that doubled the chromosome number

dimerization

When a nucleotide binds with a neighboring nucleotide instead of its complementary nucleotide

Beta Galactosidease

When glucose is absent and Lactose is present Beta G will convert a small amount of lactose to allolactose which acts as the inducer.

alloploidy

a change in chromosome number between an individual and its offspring, Polyploid organism that contains the genomes of two or more different species.

SWI/SNF

a group of proteins that are used in ATP -dependent chromatin remodeling. In this process the energy from APT hydrolysis is used to drive a change in the structure of the nucleosome and thereby makes the DNA more accessible for transcription. SWI/SNF are found in all eukaryotic species. The structural change may involve a change in the spacing of nucleosomes in relationship to one another.

Operon

a group of two or more genes under the transcriptional control of a single promoter

a corepressor binds to

a repressor

Inducer

a small effector molecule that causes transcription to increase. It can do this in 2 ways 1. bind to a repressor and prevent it from binding to the DNA 2. bind to an activator protein and cause it to bing to the DNA

Corepressor

a small molecule that binds to a repressor protein thereby causing the to bind to the DNA.

an inhibitor binds to an

activator

histone acetyltransferases

an enzyme the plays a roll in the chromatin structure remodeling. The DNA is tightly bound around the Histone often preventing replication. The amino terminal tail can be modified to alter the chromatin compaction. Histone acetyltransferases attaches an acetyl group (-CHCH3) to the lysine and eliminated the positive charge. This may loosen the structure of the nucleosome and the 30 nm fiber and thereby facilitate the ability of the RNA pol to transcribe the gene.

During catabolic repression what does glucose use as the Effector molecule?

cAMP

Regulatory proteins work with

effector molecules

effector molecules

exert their effect by binding to an activator or repressor. The binding of the effector molecule causes a conformational change in the regulatory protein and there by influencing whether of not the protein can bind to the DNA.

Inducible

gene activity that is normally off however it can be turned on via an inducer which will bind a repressor protein and prevent it from binding to DNA or it could bind to an activator protein and cause it to bind to DNA

Repressible

gene activity that is normally on however it can be turned off via the use of an coreprssor or an inhibitor. A corepressor is a small molecule that binds to a repressor protein and thereby causing the protein to bind to DNA. An inhibitor acts by binding to an activator protein and prevents transcription

Constitutive gene expression

gene expression that is constant.

constitutive genes

genes that are transcribed all the time.

Trans-acting factor

genetic regulation that can occur even though two genes are not adjacent. the actions of the lac repressor on the lac operon is a trans-effect.

Catabolite repression

in the presence of abundant glucose, the diminished synthesis of catabolic enzymes for other energy sources, specifically lactose

allolactose is the _______ for the lac repressor protein

inducer

Because the lac operon is off by default it is said to be

inducible

Repressor

is a regulatory protein that binds to the DNA and inhibits transcription

Activator

is a regulatory protein that increases the rate of transcription

Operator site (lacO)

is a sequence of bases that provides a binding site for a repressor protein

Promoter

is found in a DNA sequence to incite replication. The promoter will have a -10 region (TATA box) and a -35 region (Consensus sequence)

lac operon control by an activator protein

known as Catabolic repression and it involves cAMP and CAP

Lac operon consists of

lacZ LacY LacA CAP site Lac promoter Operator site

polycistronic mRNA

mRNA that includes coding regions for two or more structural genes.

If an inhibitor binds to an activator protein

no transcription occurs

regulatory proteins are give their name based

on how they effect transcription when they are bound to DNA

Both inhibitors and corepressors act to

reduce the rate of transcription

RNA editing

refers to a change in the nucleotide sequence of an RNA molecule that involves additions of deletions of particular bases or a conversion of one type of base to another such as a cytosine to uracil. This can have various effects such as generating start codons, generating stop codons and changing the coding sequence for a polypeptide.

Presence of allolactose

the binding of allolactose causes a confirmation change that prevents the lac repressor from binding to the operator site.

Ara operon

the operon that controls the metabolism of arabinos. The Ara operon can function as a negative or positive regulator of transcription.

Adaptor hypothesis

the position of an AA within a polypedtide chain is determined by the binding between the mRNA and an adoaptor molecule carrying a specific AA. Later work suggested that the adaptor molecule is tRNA. During translation a tRNA has two functions 1) it recognizes a three base codon sequence in mRNA and 2) it carries an AA specific for that codon.

The presence of glucose leads to

the repression of the lac operon

Hershey Chase experiment

this experiment was used to show that DNA was the genetic material. They used a bacteriophage witch is a DNA molecule surrounded by a protein coat. In the first experiment the DNA was not marked but the coat was radioactively marked. The result was cells that contained no radioactive material. In the second experiment the DNA in the phage was marked with P32, and the subsequent offspring had marked DNA

If an inducer binds to a repressor protein

transcription occurs

Negative control

transcription regulation by a repressor protein

Positive control

transcription regulation by an activator protein