AP Bio- U6 Ch 18

operon

a group of genes with related functions under the control of a single operator -includes the operator, promoter, and the genes they control

Differentiation

a process cells go through at the molecular level (determination) which puts a cell on an irreversible specialized path -requires a specific combination of several regulatory proteins to differentiate

repressor

a protein that binds to the operator and suppresses the gene by blocking attachment of RNA polymerase to the promoter -specific to its operon

structural genes

genes in the operon that code for proteins

regulatory genes

genes that surround and control the operon by controlling the operator

heterochromatin

highly condensed chromatin, doesn't allow for transcription

repressible operon

positive gene regulation- an operon that is usually on unless repressed

cell to cell signals (inductive signals)

result from molecules being sent from cell to cell induction- signals telling neighboring cells what to do

causes of cancer

spontaneous mutations- random environmental influences- chemical carcinogens, x-rays, some viruses

differential gene expression

the expression of different sets of genes by cells with the same genome

corepressor

a small molecule that binds to the repressor to make it active (allosteric regulation)

inducer

a small molecule that inactivates the repressor -helps cells avoid making unnecessary proteins/ waste energy

cell differentiation and morphogenesis are controlled by...

cytoplasmic determinants and inductive signals

alternative RNA splicing

different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons/ introns -intron/ exon shuffling leads to more proteins -its not rearranging the order, but changing the number of exons being put into the protein -significantly expands the repertoire of a set of genes

zygote transformation results from...

-cell division -differentiation -morphogenesis

feedback inhibition

allows cells to adapt to short term fluctuations in substance supply as needed (bacteria are constantly responding to changes in their environment and can adjust the activity of existing enzymes) -occurs at the level of transcription

cAMP

an activator that binds to DNA and stimulates transcription

tumor suppressor genes

encode genes that prevent uncontrolled cell growth p53 gene- causes apoptosis, a mutation in it means no apoptosis and the cell cycle doesn't stop

morphogens

gradients of substances that establish an embryo's axes and other features of its forms (determine polarity and position)

euchromatin

loosely packed chromatin, allows RNA polymerase to bind to it

homeotic genes

master control genes that control pattern formation

cytoplasmic determinants

molecules in the egg cells that influence the course of early development -regulate the expression of genes that affect the developmental fate of the cell

oncogenes

mutated proto-oncogenes that can lead to cancer ex- RAS gene- G protein is constantly on and triggering the cell cycle

inducible operon

negative gene regulation- an operon that is usually off but can be stimulated and switched on

control elements

segments of noncoding DNA in eukaryotic genes that help regulate transcription by binding to certain proteins (usually activators) proximal CE- found close to the gene Distal CE- found further from the gene, come into contact when DNA bends

pattern formation

sets up the body plan and is the result of cytoplasmic determinants and inductive signals -uneven distribution of chemicals called morphogens help establish these axis's

promoter

specific region of a gene where RNA polymerase can bind and begin transcription

gene regulation

the altering of gene expression in response to changes in the environment -important in the development of different cell types and expression of different genes

proto-oncogenes

the normal version of oncogenes; they code for proteins that stimulate normal cell cycle

morphogenesis

the physical process that gives an organism its shape

determination

the point at which an embryonic cell is irreversibly committed to becoming a particular cell type

operator

the segment of DNA that is the on/off switch and controls the access of RNA polymerase to genes

control of transcription initiation

transcription factors- attach to promoter and speed up initiation and therefore transcription chromatin modifying enzymes- provide initial control of gene expression by making a region of DNA more or less available for transcription

control of translation initiation

transport channels- determine how efficiently mRNA moves through nuclear pores to the cytoplasm -enzyme degradation of mRNA (doesn't last forever) -availability of amino acids for translation -posttranslational modifications: phosphorylation -synthesis and degradation of proteins (ubiquitin)

DNA methylation

turns off transcription by by adding a methyl group and causing chromatin to wind back up

histone acetylation

turns on transcription by creating more space for RNA polymerase to attach

coordinate control

when a single on/off switch can control a group of genes with the same function (transcription unit)