Chapter 18: Regulation of gene expression

What is a metabolic pathway?

series of chemical reactions in which the product of one reaction is the substrate for the next reaction

How can cells regulate metabolic pathways?

feedback inhibition of enzyme activity or production of enzymes

How would we produce the enzymes to regualte metabolic pathways?

Transcription of the corresponding genes

What makes a cluster of genes functionally related?

collaboration within the same metabolic

pathway

What is an operator?

A DNA sequence located near the promoter

What is the promoter region?

A specific sequence of DNA bases at the start of a gene on the sense strand where RNA polymerase binds.

What is an operon?

the whole stretch of DNA that includes the promoter, the

operator and the genes that they control

How can we switch an operon off?

a repressor that binds to the operator, preventing

the RNA polymerase to attach

Is a repressor active or inactive?

It can be either

What does a repressor do?

It can bind with another molecule called

the corepressor, which is usually related to the metabolic pathway controlled by

the operon

What is a corepressor?

a molecule that cooperates with a repressor protein to switch an operon off

What is a repressible operon?

The operon is usually "on". The repressor is inactive.

What does the product of the operon do.

Acts as the corepressor if there is excess product

What metabolic pathways are repressible operons related to?

anabolic pathways

What is an inducible operon?

An operon that is usually off. The repressor is active and attached to the

operator

What is gene expression important for in pluricellular organisms.

Cell specialization and communication

Do cells of the same organisms share the same genes?

mostly yes, but only a few genes are expressed

What is regulation in transcription?

control of gene expression at the level of transcription

What is chromatin regulation?

heterochromatin not being expressed and euchromatin being expressed. position of nucleosome plays a role

What is DNA methylation?

Addition of methyl group to DNA. associated with low transcription.

What is histone acetylation?

the addition of an acetyl group to an amino acid in a histone tail

What are control elements?

sequences recognized by transcription factors that facilitate the attachment of the RNA polymerase to the promoter

What is the term for distal control elements?

enhancer sequences

What are transcription factors?

is a protein that regulates gene expression by binding to specific DNA sequences. Allows for RNA polymerase to attach.

Is RNA able to attach by itself?

No

What are activation sequences?

DNA regions that help initiate or enhance the transcription of a gene.

What do activation sequences and transcription control have to do in order to be efficient?

Match each other.

Do eukaryotic genes get organized in operons?

No, but related genes have the same control sequences and react to the same controls

What is post-transcriptional regulation?

essentially alternative splicing

What is post-translational regulation?

Newly synthetized proteins may undergo processing, and can be marked for degredation.

What is the non-coding genome transcribed into?

ncRNA

What are the non-coding RNA's

miRNA and siRNA

What is Micro-RNA?

small sequences that bind with some

sequences of mRNA and either cause degradation of this mRNA or block

its translation

What is Small Interfering RNA?

Similar to miRNA, they silence gene expression by degrading mRNA.

What drives the embryonic development program?

gene expression

What sets up the program for gene expression in the egg?

cytoplasmic determinants

What are cytoplasmic determinants?

maternal substances in the egg that influence early development

How does cell division impact cytoplasmic determinants?

cell division splits these determinants non-evenly, which influences

their future development

Do the cells communicate with each other at this stage?

yes

What is pattern formation?

The development of a spatial organization of tissues and organs.

What is the first step of pattern formation?

establishment of polarity axes

How is cell development controlled?

By positional information via molecules

What is the beginning of pattern formation and spatial organization?

Determinants in an unfertilized egg

How does cell division affect this?

creates specific areas (segments) that will express some

specific factors

What about in later stages?

homeotic genes control patterns formation

What animal was it where this experiment took place?

Fruit fly

Do mammals have similar system?

yes

What is macroevolution?

creation of novel body shapes

What is the result of mutation in developmental genes?

Macroevolution

How does cancer form

default in gene regulation for cell division

What is a proto-oncogene?

genes that code for proteins that stimulate normal growth

and cell division

What happens if a protooncogene becomes mutated?

it becomes an oncogene (unregualted)

What can cause the mutation in a proto-oncogene?

It can result from an increase of gene activity or the protein activity

What inhibits cell division?

Tumor-suppressor genes

What is the proto-oncogene ras.

a G-protein that relay the signal of growth factors received by a receptor

What happens if the ras protein is mutated?

the G-protein remains active, and the signal is transmitted even

without growth factors

What does Tumor-suppressor p53 do?

controls damages in cell DNA, can inhibit the cell cycle, can trigger genes involved in DNA repair, and can even trigger apoptosis.

What happens if p53 is mutated?

it does not prevent cell division?

What does cancer result from?

a series of mutation that affect proto-oncogenes and tumor suppressor genes.

What happens if a virus integrates its DNA with cell DNA?

it interferes with normal gene regulation?