Biology Ch.18

Front 1

how is gene expresion controlled by regulating transcription?

Back 1

binding protein to regulatory sequence blocks transcription by getting in the way of rna polyermase, or stimulates transcrip. by facilitating binding rna polyermase to the promoter

Front 2

what is transcriptional control in prokaryotes?

Back 2

adjusts cell's activities to immmediate, external environment to grow and divide as rapidly as possible

Front 3

what is transcriptional control in eukaryotes?

Back 3

-most common
-primary funct. is maintaining gene control
-compensate for physiological cnages or mediate product, decisions

Front 4

what is posttranscriptional control?

Back 4

influencing mRNA produced from genes or the activity of proteins encoded by the mRNA

Front 5

what is a major groove?

Back 5

-proteins can bind to outside surface of double helix
-nucleotides' hydrophobic methyl groups, hydrogen atoms, and hydrogen bond donors & acceptors protrude from major groove
-employ bends in protein chain that permit interlocking w/major groove (dna-binding motifs)

Front 6

describe the helix-turn-helix motif.

Back 6

-one helical segment fits snuggly in major groove, other butts against outside of dna molecule
-two binding sites doubles contact zone and greatly strengthens the bond

Front 7

describe the homeodomain motif.

Back 7

-special kind of helix-turn-helix motif surrounded by region initiating key develop. stages

Front 8

describe the zinc finger motif.

Back 8

-zinc atoms coordinate dna binding
-the more zinc fingers in cluster, the stronger the protein binds to dna

Front 9

describe the leucine zipper motif.

Back 9

-formed when region on one subunit containing several hydrophobic amino acids interacts w/similar region on another subunit

Front 10

what is a lac operon?

Back 10

multi. genes are part of a single gene expression unit.

Front 11

what do basal transcription factors do?

Back 11

they are necessary to eestablish productive initiation; do not increase the rate

Front 12

what do specific transcription factors do?

Back 12

they act in a tissue-or time-dependent manner to stimulate higher levels of transcription than the basal levels

Front 13

what are enhancers?

Back 13

binding site of specific transcription factors;accomplished by dna bending to form a loop, positioning the enhancer close to the promoter

Front 14

why is transcriptional control more complicated in eurkayotes than in prokaryotes?

Back 14

-dna organized in chromatin
-transcrip. occurs in nuclues & translat. in cytoplasm
-complex developm. programs
-multiple tissue types

Front 15

what is one effect of chromatin structure on gene expression?

Back 15

promoter blocking by nucleosomes

Front 16

what does dna methylation do?

Back 16

blocks accidental transcription of "turned off" genes

Front 17

what does posttranscriptional control on eukaryotes involve?

Back 17

invovles the recognition of specific sequences on primary rna transcript. by regulatory proteins and small rna molecules

Front 18

how does rna interference work?

Back 18

gene silencing happens when a change in gene expression is passed from one generation to another; appears to play a major role in epigenetic change

Front 19

what is alternative splicing?

Back 19

exons can be spliced together in dif. ways to assemble a variety of polypeptides

Front 20

describe the transport of the transcript out of the nucleus.

Back 20

passage out of mRNA transcript across nuclear membrane requires the transcript to be recognized

Front 21

what do translation repressor proteins do?

Back 21

shut-down translation by binding to the beginning of the transcript so that it can't attach to the ribosome