transcriptional regulation

Question 1

explain how oestrogen in chicken eggs is an example of hormonal control of transcription

Answer 1

oestrogen increases the transcription of the gene that encodes ovalbumin
it also triggers production of progesterone, which increases transcription of the gene for avidin
also changes cell behaviour; increases cilia motility causes egg to move down oviduct

Question 2

how do steroid hormones regulate gene expression?

Answer 2

1) hormone binds receptor -> conformational change

2) hormone-receptor complex binds DNA, affecting transcription

Question 3

explain how signal transduction regulates gene expression

Answer 3

1) ligand binds transmembrane receptor, activating the intracellular domain
2) kinases cause phosphorylation cascade
3) activation of transcription factors

Question 4

what are the direct and indirect ways in which transcription factors alter gene expression?

Answer 4

direct: interacting with transcriptional machinery
indirect: modulation of chromatin structure

Question 5

explain how promoters such as the TATA box can initiate transcription

Answer 5

TATA box located 30bp downstream of start codon
positions RNAP II to begin transcription.
DNA binds to TATA sequence in the minor groove, making DNA more accessible to RNAP II

Question 6

what are inhancers?

Answer 6

transcription factors which increase transcription by causing increased interaction of proteins with the RNAP II complex

Question 7

how can chromatin structure be altered to regulate transcription?

Answer 7

by modification of the N-terminal histone tail

Question 8

what are HATs and HDACs?

Answer 8

HATs: histone acetyltransferases, make chromatin more loose
HDACs: histone deactylases, repress transcription by making chromatin less loose