Gene regulation

Question 1

constitutive genes:

Answer 1

genes expressed all the time

Question 2

regulated genes:

Answer 2

genes only expressed when needed

Question 3

housekeeping proteins: and eg

Answer 3

• proteins which are always needed

- ribosomal proteins

Question 4

how does a cell regulate production of proteins:

Answer 4

• feedback inhibition

- gene regulation

Question 5

prokaryotes: feedback inhibition

Answer 5

• activity of first enzyme in pathway stoped by end product

Question 6

prokaryotes: gene regulation

Answer 6

• gene coding for enzymes in metabolic pathway are controlled

Question 7

prokaryotes: operon general features

Answer 7

• prokaryote genes often arranged in operons
• same genes under control of single promotor
• all necessary proteins produced at same time in response to same stimulus

Question 8

operons: list parts

Answer 8

• operator
• promoter
• genes that they control

Question 9

operons: operator

Answer 9

• regulatory ‘switch’

- segment of DNA positioned within the promotor

Question 10

operons: switched off by

Answer 10

protein repressor

Question 11

operons: repressor

Answer 11

• prevents gene transcription by binding to operator

- blocking RNA polymerase

Question 12

operons: what codes for repressor protein

Answer 12

• by regulatory gene

- located elsewhere in genome (co-repressor is tryptophan)

Question 13

repressible operons:

Answer 13

• usually on

- binding a repressor to operator will shit off transcription

Question 14

repressible enzymes: function when

Answer 14

• in anabolic (creating metabolites) pathways
• synthesis repressed by high levels of end product
• eg. tryptophan synthesis

Question 15

inducible operons:

Answer 15

• usually off

- inducer inactivates repressor to turn on transcription

Question 16

inducible enzymes: function when

Answer 16

• in catabolic (breaking down metabolic) pathways
• synthesis induced by chemical signal
• eg. lactose

Question 17

lactose: general features

Answer 17

• major sugar of milk
• uncommon nutrient for bacteria
• enzymes for lactose metabolism usually not expressed (conserve energy)

Question 18

lactose: energy for cells

Answer 18

• cells use glucose for energy

- lactose: disaccharide of glucose and galactose

Question 19

lac operon: list enzymes involved

Answer 19

• permease
• b-galactosidase
• transacetylase

Question 20

lac operon: permease

Answer 20

• allows lactose to enter bacterial cell

Question 21

lac operon: b-galactosidase

Answer 21

• breaks down lactose to glucose and galactose

Question 22

lac operon: transacetylase

Answer 22

unknown function, assists lactose breakdown

Question 23

lac operon: lac I

Answer 23

• control gene
• encodes lac repressor protein
• when bound to DNA (operator) will prevent transcription at lac operon

Question 24

lac operon: inducer

Answer 24

• form of lactose

- binds to repressor protein and inactivates it -> transcription of lac operon

Question 25

negative control:

Answer 25

- both inducible and repressible operons involve negative control of genes (via repressor)

Question 26

positive control:

Answer 26

- regulatory protein that switches transcription on | - eg. CRP activity in lac operon

Question 27

when is CRP inactive:

Answer 27

- if glucose and lactose is present | - reduced expression of lac operon

Question 28

when is CRP active:

Answer 28

- lactose present - no glucose - high levels of lac operon transcription

Question 29

eukaryotes: gene transcription

Answer 29

- multiple control elements | - segments of noncoding DNA act as binding sites for transcription factors (help regulate transcription)

Question 30

eukaryotes: what are critical to precise regulation of gene expression in different cell types

Answer 30

- control elements | - transcription factors

Question 31

proximal control elements:

Answer 31

- located close to promotor

Question 32

distal control elements:

Answer 32

- groupings of enhancers | - may be far away from a gene or even located in an intron

Question 33

where do transcription factors bind:

Answer 33

- to TATA box within promoter/ other proteins/ transcription factors or RNA polymerase

Question 34

when does complete transcription occur:

Answer 34

- when complete transcription initiation complex is assembled - eg. RNA polymerase and transcription factors

Question 35

how can some transcription factors also function as:

Answer 35

repressors

Question 36

an enhancer has:

Answer 36

- 10 control elements

Question 37

control element:

Answer 37

- binds 1-2 specific transcription factors

Question 38

combo of control elements important:

Answer 38

- in transcription regulation

Question 39

coordinated transcription: features

Answer 39

- unlike genes of prokaryotic operon, co-expressed eukaryotic genes have promoter and control elements - genes can be scattered over different chromosomes but each has same combo of control elements

Question 40

copies of activators recognise specific control elements and promote:

Answer 40

simultaneous transcription of the genes

Question 41

post-transcriptional regulation:

Answer 41

- mRNA only codes for a protein-> the protein that carries out the function

Question 42

after transcription we can have:

Answer 42

- alternative RNA splicing - block translation with regulatory proteins that prevent attachment of mRNA to ribosome - regulation of post-translational modification of protein

Question 43

cell differentiation:

Answer 43

- process of cells becoming specialised in structure and function

Question 44

stem cell:

Answer 44

- relatively unspecialised cell that can reproduce itself indefinitely and differentiate into specialised cells of one or more types

Question 45

embryonic stem cell:

Answer 45

- isolated from early embryo which are able to differentiate into all cell types

Question 46

do adults have stem cells:

Answer 46

- yes | - replace non-reproducing cells as needed

Question 47

totipotent stem cells:

Answer 47

- obtained from early embryos, spores, plant calluses | - give rise to complete individual

Question 48

pluripotent stem cells:

Answer 48

- give rise to many different cell types | - cannot produce entire individual

Question 49

multipotent stem cell:

Answer 49

- gives rise to different cell types within tissues

Question 50

induces pluripotent stem cells (iPS):

Answer 50

- potentially used to treat repair of damaged tissue in adults - using skin cells, reprogramming them

Question 51

proto-oncogene:

Answer 51

normal version of a gene

Question 52

oncogene:

Answer 52

cancer causing gene