11.8

Question 1

imprinting

Answer 1

one allele is expressed

epigenetic

Question 2

how to silence a gene

Answer 2

1. dna methylation
2. histone modification
3. binding of long ncRNA

established in the germline

Question 3

Xi

Answer 3

X-inactivation occurs early in development
- irreversible
females have only 1 active X chromosome

the inactive chromosome is very condensed and packaged in HETEROCHROMATIN

Question 4

gene products

Answer 4

all polypeptides are gene products, but not all gene products are polypeptides. some gene products are tRNA and rRNA. microfilaments and other elements of the cytoskeleton (collagen) and many other polypeptides are not enzymes

Question 5

repressible/inducible

Answer 5

repressible -> anabolic enzymes whose transcription is inhibited in the presence of excess product

inducible -> catabolic enzymes whose transcription is stimulated by abundance of substrate

Question 6

Lac Operon (DNS)

Answer 6

DNS

Question 7

regulation of eukaryotes

Answer 7

complex - happens at initiation

UCE (upstream control elements) 200 bps upstream from initiation

core promoter (50 bps upstream from transcription)

TATA box -25 – highly conserved DNA recognition sequence, TBP binds to TATA box to initiate transcription complex assembly at the promoter

Question 8

enhancer (eukaryotic transcriptional regulation)

Answer 8

enhancer sequences in DNA are bound by activator proteins, a type of Transcriptional regulation

located thousands of bps away from promoter, still regulates (DNA looping)

Question 9

gene repressor proteins

Answer 9

eukaryotic method of inhibiting transcription

modify chromatin structure

transcription factors -> DNA binding domains crucial in transcriptional regulation, bind to promoters or other regulatory sequences

extracellular signals -> affects binding of transcriptional machinery

Question 10

eukaryotic transcriptional regulation (3 other methods)

Answer 10

RNA translocation - where mRNA transcripts are sent (localization must occur before translation begins: neuron have polarity, some transcripts are sent to dendrites)

mRNA surveillance - mRNAs must be high quality
RNA interference - RNAi silences gene expression after a transcript has been made (mediated by miRNA and siRNA)

Question 11

translational control

Answer 11

limited control

Question 12

post-translational events

Answer 12

proteins don’t just function after they are produced
they need to be covalently modified
chaperones -> important for folding in all organisms
covalent modification -> addition of fatty acid

proteins can be

• acetylated
• formylated
• alkylated
• glycosylated
• phosphorylated
• sulphated

Question 13

zymogen

Answer 13

protein-precursor - safety reasons

preproinsulin -> proinsulin -> insulin

three cleavage events (occur in a secretory vesicle)

Question 14

DNA replication, transcription, and translation Table DRAW (p. 249)

Answer 14

see differences