transcriptional level control

Question 1

how is gene expression controlled at the transcriptional level

Answer 1

by transcription factors

Question 2

what is a transcription factor

Answer 2

proteins that bind to DNA and switch genes on and off by either increasing or decreasing transcription rate

Question 3

what are factors that increase transcription known as

Answer 3

activators

Question 4

what are factors that decrease transcription known as

Answer 4

repressors

Question 5

what does the shape of a transcription factor determine

Answer 5

whether or not it is able to bind to DNA

Question 6

where does transcription factors bind in eukaryotes

Answer 6

specific DNA sites at the start of their target gene

Question 7

where do transcription factors bind to in prokaryotes

Answer 7

operons

Question 8

what is an operon

Answer 8

a section of DNA that contains a cluster of structural genes, a control element and sometimes regulatory genes

Question 9

what is a structural gene

Answer 9

genes that code for useful proteins (enzymes and hormones)

Question 10

what do control elements contain

Answer 10

promoter
operator

Question 11

what is a promoter

Answer 11

a DNA sequence located before the structural genes where RNA polymerase binds

Question 12

what is an operator

Answer 12

a DNA sequence where transcription factors bind

Question 13

what is a regulatory gene

Answer 13

gene that codes for an activator or a repressor

Question 14

when does e coli respire using lactose

Answer 14

when glucose is not available

Question 15

where are the genes found that code for enzymes to respire lactose in e coli

Answer 15

the lac operon

Question 16

what are the 3 structural genes in the lac operon

Answer 16

lac Z, lac Y and lac A

Question 17

what do the structural genes in the lac operon help produce

Answer 17

proteins that help lactose be hydrolysed (b-galactosidase and lactose permease)

Question 18

what happens when lactose is not present at the lac operon (4)

Answer 18

1. regulatory gene (lacL) produces the lac repressor
2. lac repressor binds to the operator site
3. blocks transcription as RNA polymerase cannot bind to the promoter region
4. structural genes, lacZ, lacY and lacA are not transcribed

Question 19

what happens when lactose is present at the lac operon

Answer 19

1. lactose binds to repressor
2. repressor changes shape so it can no longer bind to operator
3. RNA polymerase binds to promoter region and can transcribe the structural genes
4. structural genes code for enzymes to hydrolyse into glucose for respiration