Regulation of transcription and translation

Question 1

What are transcription factors?

Answer 1

Proteins which control the transcription of genes

Question 2

Where are promoters found?

Answer 2

At the start of the target gene

Question 3

What are promoters?

Answer 3

Specific DNA sites which the transcription factors bind to

Question 4

What are target genes?

Answer 4

The genes that transcription factors control the expression of

Question 5

What are the two types of transcription factor?

Answer 5

activators

repressors

Question 6

What do activators do?

Answer 6

They stimulate or increase the rate of transcription

Question 7

What do repressors do?

Answer 7

They decrease or inhibit the rate of transcription

Question 8

How do activators work?

Answer 8

They help RNA polymerase to bind to the target gene and activate transcription

Question 9

How do repressors work?

Answer 9

They bind to the start of the target gene to prevent RNA polymerase from binding

Question 10

What is oestrogen?

Answer 10

A steroid hormone that can affect transcription

Question 11

What does oestrogen bind to?

Answer 11

Transcription factor called an oestrogen-receptor to form an oestrogen-oestrogen receptor complex

Question 12

Where does the oestrogen-oestrogen receptor complex move from and to?

Answer 12

From the cytoplasm to the nucleus

Question 13

Where does the oestrogen-oestrogen receptor complex bind?

Answer 13

Specific DNA sites near the start of the target gene

Question 14

What is RNAi?

Answer 14

RNA interference

Small double-stranded RNA molecules stop mRNA from target genes from being translated into proteins

Question 15

What are the two types of RNAi involved?

Answer 15

siRNA

miRNA

Question 16

What is the process involving siRNA?

Answer 16

• Double stranded siRNA associates with several proteins and unwinds
• One of the single strands of siRNA is selected and the other strand is degraded
• The single strand of siRNA then binds to the target mRNA
• The base sequence of the siRNA is complimentary to the base sequence in sections of the target mRNA
• The proteins associated with the siRNA cut the mRNA into fragments so it is no longer translated
• The fragments then move into a processing body which contains the tools to degrade them

Question 17

What is the process involving miRNA?

Answer 17

• the miRNA isn’t fully complimentary to the target mRNA which makes it less specific than siRNA and so it may target more than one RNA molecule
• when miRNA is first transcribed, it exists as a long, folded strand and it is processed into a double strand and then into two single strands by enzymes in the cytoplasm
• One strand associates with proteins and binds to target mRNA in the cytoplasm.
• Instead of the proteins associated with the miRNA cutting mRNA into fragments, the miRNA-protein complex physically blocks the translation of the target mRNA
• The mRNA is then moved into a processing body to be either stored or degraded