Unit 17- Gene expression

Question 1

eukaryotic gene regulation

Answer 1

• each gene has its own promoter and is transcribed separately
• DNA must unwind from the histone proteins before transcription
• transcription and translation are separated in time and space

Question 2

DNase I hypersensitivity

Answer 2

DNase I hypersensitive site: more open chromatin configuration site

Question 3

Histone modification

Answer 3

• addition of methyl groups to the histone protein tails
  
  • depending on which area is methylated- either activation or repression
• addition of acetyl groups to histone protein tails
  
  • associated with activation

Question 4

chromatin remodeling complexes

Answer 4

reposition the nucleosomes (8 histones and DNA), allowing transcription factors and RNA polymerase to bind to promoters and initiate transcription

Question 5

flowering in Arabidopsis

Answer 5

• controled by acetylation of histones
• flowering locus C (FLC) gene (*regulator protein: represses flowering)
• flowering locus D (FLD) gene (deacetylase enzyme: removes acetyl groups. activates flowering)

Question 6

DNA methylation

Answer 6

DNA methylation of cytosine bases adjacent to guanine nucleotides (CpG)- “CpG islands”

Question 7

chromatin immunoprecipitation sequencing (ChIP-seq)

Answer 7

can be used to indentify DNA-binding sites of a specific protein and the locations of modified histone proteins

Question 8

transcription factors

Answer 8

• stimulate and stabilize basal transcription apparatus at core promoter
• mediator

Question 9

enhancers

Answer 9

DNA seq stimulating transcription a distance away from promoter

Question 10

silencer

Answer 10

DNA seq with an inhibitory effect on the transcription of distant genes
- position and orientation independent, and they can obtain binding sites for transcription factors that dec transcription

Question 11

insulators

Answer 11

• DNA seq that blocks or insulates the effect of enhancers
• may function by causing loops of chromatin that may form interacting regions of genes and regulatory elements

Question 12

insulators and their binding proteins…

Answer 12

may help create “neighborhoods” of regulatory elements and genes that are able to physically interact but are insulated from regulatory elements in other neighborhoods

Question 13

regulation of transcriptional stalling and elongation

Answer 13

• at some genes, RNA polymerase may pause or stall downstream of the promoter
  
  • heat shocked genes are stalled until heat stress is encountered
• regulatory factors affect stalling and the elongation of transcription.

Question 14

response elements

Answer 14

common regulatory elements upstream of the start sites of a collective group of genes in response to a common environmental stimulus.

Question 15

sex determination in drosophilia

Answer 15

alternative splicing of tra pre-mRNA.

Question 16

Dicer and RISC

Answer 16

RNA-induced silencing complex

Dicer: cleaves and processes double-stranded RNA to produce siRNAs or miRNAs 21-25 nuclotides long which combine with proteins to form RISC

RISC: pairs with complementary base seqs in specific mRNA molecs (often 3’ UTR of mRNA)

small interfering RNAs base-pair perfectly with mrNAs (microRNAs often form less-than-perfect pairings)

Question 17

RNA cleavage

Answer 17

RISC containing an siRNA, pair with mRNA molecs and cleave mRNA

Question 18

inhibition of translaion

Answer 18

miRNAs bind to mRNA, disallowing translation

Question 19

Transcriptional silencing

Answer 19

altering chromatin structure (small RNAs bind to DNA and attract methylases to specific histone tails)

Question 20

Slicer-independent degradation of mRNA

Answer 20

miRNA attracts Dicer and RISC to cleave mRNA

Question 21

what affects the rate of translation?

Answer 21

availability of ribosomes, charged tRNas, and initation and elongation factors

Question 22

eukaryotic gene control

Answer 22

level of regulation: primarily