Ch. 11 Key Words Genetics

Front 1

activation domain

Back 1

a part of a transcription factor required for the activation of target-gene transcription; it may bind to components of the transcriptional machinery or may recruit proteins that modify chromatin structure or both

Front 2

Barr body

Back 2

a densely staining mass that represents an inactivated X chromasome

Front 3

barrier insulator

Back 3

a DNA element that prevents the spread of heterochromatin by serving as a binding site for proteins that maintain euchromatic chromatin modifications such as histone acetylation

Front 4

chromatin remodeling

Back 4

changes in nucleosome position along DNA

Front 5

coactivator

Back 5

a special class of eukaryotic regulatory complex that serves as a bridge to bring together regulatory proteins and RNA polymerase II

Front 6

constitutive heterochromatin

Back 6

chromosomal regions of permanently condensed chromatin usually around the telomeres and centromeres

Front 7

corepressor

Back 7

a protein or protein complex that acts in concert with a repressor protein to repress transcription, often by modifying chromatin structure; usually not a DNA-binding entity itself

Front 8

dosage compensation

Back 8

the process in organisms using a chromosomal sex-determination mechanism (such as XX vs XY) that allows standard structural genes on the sex chromosomes to be expressed at the same levels in females and in males, regardless of the number of sex chromosomes. in mammals, dosage compensation operates by maintaining only a single active X chromosome in each cell; in Drosophila, it operates by hyperactivating the male X chromosome

Front 9

enhanceosome

Back 9

the macromolecular assembly responsible for interaction between enhancer elements and the promoter regions of genes

Front 10

enhancer (element/mutation)

Back 10

element: a cis-acting regulatory sequence that can elevate levels of transcription from an adjacent promoter. many tissue specific enhancers can determine spatial patterns of gene expression in higher eukaryotes. enhancers can act on promoters over many tens of kilobases of DNA and can be 5' or 3' of the promoters that they regulate
mutation: a modifier mutation that makes the phenotype of mutation of another gene more severe

Front 11

enhancer-blocking insulator

Back 11

regulatory elements postioned between a promoter and an enhancer. their presence prevents the promoter from being activated by the enhancer

Front 12

epigenetic inheritance

Back 12

heritable modifications in gene function not due to changes in the base sequence of the DNA of the organism, examples are paramutation, x-chromosome inactivation, and parental imprinting

Front 13

epigenetic mark

Back 13

a heritable alteration, such as DNA methylation or a histone modification, that leaves the DNA sequence unchanged

Front 14

epigenetic silencing

Back 14

the reversable alteration of a gene due to chromatin structure

Front 15

euchromatin

Back 15

a less-condensed chromosomal region, thought to contain most of the normally functioning genes

Front 16

gene silencing

Back 16

a gene that is not expressed owing to epigenetic regulation. unlike genes that are mutant due to DNA sequence alterations, genes inactivated by silencing can be reactivated

Front 17

genomic imprinting

Back 17

a phenomenon in which a gene inherited form one of the parents is not expressed, even though both gene copies are functional.imprinted genes are methylated and inactivated in the formation of male or female gametes

Front 18

hemimethylation

Back 18

where one DNA sequence where one strand is methylated and other one isn't

Front 19

heterochromatin

Back 19

densely staining condensed chromosomal regions, believed to be for the most part genetically inert

Front 20

herterochromatin protein-1

Back 20

a protein necessary for the maintenance of heterochromatin

Front 21

histone code

Back 21

refers to the pattern of modification (eg acetylation, methylation, phosphorylation) of the histone tails that may carry information required for correct chromatin assembly

Front 22

histone deacetylase (HDAT)

Back 22

the enxymatic activity that removes an acetyle group from a histone tail, which promotes the pression of gene transcription

Front 23

histone tail

Back 23

the end of a histone protein protruding from the core nucleosome and subjected to posttranslational modification

Front 24

hyperacetylation

Back 24

an overabundance of acetyl groups attached to certain amino acids of the histone tails. transcriptionally active chromatin is usually hyperacetylated

Front 25

hypoacetylation

Back 25

an underabundance of acetyle groups on certain amino acids of the histone tails. transcriptionally inactive chromatin is usually hypoacetylated

Front 26

maternal imprinting

Back 26

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 th ecourse of gamete formation

Front 27

mediator complex

Back 27

a protein complex that acts as an adaptor that interacts with transcription factors bound to regulatory sites and with general initiation factors and RNA polymerase II-mediated transcription

Front 28

monoallelic inheritance

Back 28

inheriting one allele?

Front 29

paternal imprinting

Back 29

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

Front 30

pheromone

Back 30

a molecule that promotes mating behavior

Front 31

position-effect variegation (PEV)

Back 31

variegation causeecd byt the inactivation of a gene in some cells through its abnormal juxtaposition with heterochromatin

Front 32

promoter-proximal element

Back 32

the series of transcription-factor binding sites located near the core promoter

Front 33

reporter gene

Back 33

a gene whose phenotypic expression is easy to monitor; used to study tissue-specific promoter and enhancer activities in transgenes

Front 34

synergistic effect

Back 34

a feature of eukaryoti regulatory proteins for which the transciptional activation mediated by the interaction of several proteins is greater than the sum of the effects of the proteins taken individually

Front 35

upstream activation sequence (UAS)

Back 35

a DNA sequence of yeast located 5' of the gene promoter; a transcription factor binds to the UAS to positively regulate gene expresion