3. Regulation of Gene Expression I

Question 1

what are transcription factors?

Answer 1

a regulatory protein which travel into the nucleus and control the rate of transcription by either activating or repressing RNA polymerase

Question 2

where do transcription factors bind to, when either activating or repressing RNA polymerase?

Answer 2

the promoter region

Question 3

define the promoter region

Answer 3

the binding site of RNA polymerase

Question 4

what enzyme do transcription factors affect?

Answer 4

RNA polymerase

Question 5

how can transcription factors repress RNA polymerase?

Answer 5

as the receptors will bind to the specific receptor, which will block the promoter of the RNA polymerase.

Question 6

Oestrogen is a ___________ __________

Answer 6

transcription factor

Question 7

what is oestrogen?

Answer 7

a transcription factor
it is a short sequence of DNA within the promoter of a gene, which can bind to a specific hormone receptor complex, regulating transcription

Question 8

how does oestrogen activate or repress transcription?

Answer 8

• binds to an oestrogen receptor
• forming an oestrogen-oestrogen complex
• this moves from the cytoplasm into the nucleus
• binding to the promoter, which will either activate or repress transcription

Question 9

what is oestrogen an example of?

Answer 9

a transcription factor

Question 10

what can prevent translation?

Answer 10

interfering RNA (RNAi)

Question 11

define RNAi molecules

Answer 11

small lengths of non coding RNA,

Question 13

what is the role of RNAi

Answer 13

they regulate gene expression by affecting translation

Question 14

describe RNAi’s features

Answer 14

they are double stranded

Question 15

name two examples of RNAi’s

Answer 15

• short interfering RNA (animals)
• Micro RNA (animals and plants)

Question 16

describe how siRNAs in plants work

Answer 16

• double stranded siRNA associates with proteins in the cytoplasm and unwinds
• one siRNA strand degrades while the other binds to the target mRNA
• the protein associated with siRNA cut the mRNA into smaller fragments meaning it cannot be translated

Question 17

will miRNA always make a difference?

Answer 17

they are not fully complimentary, meaning they may not always bind to the right target mRNA

Question 18

describe how miRNA affects translation?

Answer 18

• one strand from the double stranded miRNA is degraded so that it is a single strand
• it binds to the complimentary mRNA
• this blocks the receptor and stops a ribosome from binding
• mRNA is then stored or degraded