Molecular Genetics Exam 3

a, alpha, and diploid a/alpha cells

the three cell types in the yeast mating system

a-factor

molecule released by alpha cells to initiate mating with a cells

transcriptional gene silencing

genes cannot be transcribed because they are in heterochromatin

MAT locus

locus (genes) that determines yeast mating type

position effect

expression of genes depends on their placement along a chromosome

operon

a segment of DNA that encodes a multigenic mRNA as well as adjacent promoted and regulatory regions

positive regulation

type of regulation where an activator binds to a DNA site and turns on transcription

allosteric effector molecule

molecules that bind to proteins and change their conformation

catabolite repression

the inactivation of an operon caused by the presence of large amounts of the metabolic end product of the operon

constitutive mutation

mutations that result in expression of an operon even in the absence of an inducer

operator

the cis-acting site is bound by a repressor to inactivate transcription

catabolite activator protein (cap)

the transacting protein that is activated when glucose is low

sigma-factor

the trans-acting protein in prokaryotes that recognizes the -10 and -35 sites in a promoter

promoter

cis-acting region in both prokaryotes and eukaryotes where rna polymerase binds to initiate transcription

trp repressor

in global control of the trp operon, tryptophan binds to this trans- acting protein turning off transcription of the trp operon

histone deacetylase (hdac)

removes acetyl group from histones, leading to open chromatin

rna polymerase 2

the enzymes that exclusively transcribes mrna in eukaryotes

constitutive mutations

class of mutations that result in expression of structural genes in the absence of the inducer

cAMP-CAP

the protein complex that binds to the operator in the lac operon and activates transcription when glucose is low

attenuation

in the tryptophan operon, this method of regulation involves alternative secondary structures of leader sequence

tata box

most important binding site in promoter of eukaryotes

promoter proximal elements

binding site just upstream of promoter that binds to general transcription factors

upstream activation sequence

in the gal pathway, this cis-acting site binds gal-4 to activate expression of the Gal protein coding genes

galactose

binding of this allosteric effector molecule to gal-3 activates expression of gal genes

deacetylation of histones in the gal promoter

in regulation of the yeast gal pathway, binding of tup1 to mig1 reduces transcription in this way

general transcription factors

trans-acting protein complex required for expression of all proteins in eukaryotes

gal-80

in the gal pathway, this protein represses expression in the absence of galactose

chromatin remodeling

the movement of nucleosomes to regulate expression of genes in eukaryotes

acetylation

chemical modification that neutralizes the negative charge of lysine residues in histone tails

maternal imprinting

the expression of a gene only when inherited from the father, because the copy of the gene inherited from the mother is inactive due to methylation in the course of gamete formation