6.1 Gene Expression

Question 1

what are genes that code for enzymes constantly required for respiration called?

Answer 1

housekeeping genes

Question 2

what are genes that code for protein based hormones only required at certain times called?

Answer 2

tissue specific genes

Question 3

how is expression of genes regulated?

Answer 3

switching genes on and off

increasing or decreasing the rate of product synthesis

Question 4

bacteria respond to changes in environment by expressing genes when?

Answer 4

when products are required

Question 5

what is gene regulation in multicellular organisms needed for?

Answer 5

cell specialisation

Question 6

what levels are genes regulated at?

Answer 6

transcriptional
post transcriptional
translation
post translational

Question 7

at transcriptional level what can happen to genes?

Answer 7

they can be turned on or off

Question 8

at post transcriptional level what happens to mRNA?

Answer 8

it is modified regulating transcription and the types of protein produced

Question 9

at translational level, what can happen to translation?

Answer 9

it can be stopped or started

Question 10

at post translational level what can happen to proteins?

Answer 10

they can be modified after synthesis changing their functions

Question 11

(transcriptional control) what are the different types of transcriptional control?

Answer 11

chromatin remodelling
histone modification
lac operon
cyclic AMP

Question 12

(transcriptional control) chromatin remodelling by histone modification is often called what?

Answer 12

epigenetics

Question 13

(transcriptional control) what is chromatin?

Answer 13

DNA wound around histones in eukaryotic cells

Question 14

(transcriptional control) what is heterochromatin?

Answer 14

tightly wound DNA visible during cell division

Question 15

(transcriptional control) what is euchromatin?

Answer 15

loosely wound DNA during interphase so DNA can be replicated

Question 16

(transcriptional control) why does DNA coil around histones?

Answer 16

histones are positively charged

DNA is negatively charged

Question 17

(transcriptional control) what is acetylation and what effect does it have?

Answer 17

addition of acetyl groups
reduces positive charge of histones
DNA coils less tightly allowing genes to be transcribed

Question 18

(transcriptional control) what is phosphorylation and what effect does it have?

Answer 18

addition of phosphate
reduces positive charge of histones
DNA coils less tightly allowing genes to be transcribed

Question 19

(transcriptional control) what is methylation and what effect does it have?

Answer 19

addition of methyl group
makes histones more hydrophobic
DNA binds more tightly

Question 20

(transcriptional control) what is an operon?

Answer 20

group of genes under control of same regulatory mechanism expressed at the same time

Question 21

(transcriptional control) why is an operon efficient?

Answer 21

way of saving resources

if certain gene products aren’t needed all genes switch off

Question 22

(transcriptional control) lac operon - what is a regulatory gene?

Answer 22

located near the operon

codes for a repressor protein

Question 23

(transcriptional control) lac operon - what is the repressor protein?

Answer 23

binds to operator preventing RNA polymerase binding and transcribing structural genes in absence of lactose

Question 24

(transcriptional control) lac operon - what is the lac operon?

Answer 24

group of 3 genes, lacZ, lacY and lacA involved in metabolism of lactose
code for 3 enzymes

Question 25

(transcriptional control) when lactose is present what does it do?

Answer 25

binds to the repressor protein causing it to change shape so it cant bind to the operator

Question 26

(transcriptional control) when lactose is present what can RNA polymerase do?

Answer 26

bind to the promoter

transcribing the genes so the enzymes can be synthesised

Question 27

(transcriptional control) why is the lac operon described as being leaky?

Answer 27

it is still transcribed to a limited extent even in the absence of lactose
without lactose permease (one of the enzymes produced) lactose would never be able to enter

Question 28

(transcriptional control) what is epigenetics?

Answer 28

heritable changes to gene expression in eukaryotic cells (genes switched on/off which can affect the phenotype of the cell)

Question 29

(transcriptional control) epigenetics - how can genes be silenced?

Answer 29

DNA methylation & histone modification

Question 30

(transcriptional control) epigenetics - what does the enzyme histone deacetylase remove?

Answer 30

acetyl groups from histones

causing gene silencing making the DNA histone complex more tightly packed

Question 31

(transcriptional control) epigenetics - for a epigenetic factor to be passed between generations where must it be found?

Answer 31

gametes

Question 32

(transcriptional control) epigenetics - what is a factor that affects development of bees?

Answer 32

all bee larvae are identical but if fed royal jelly with royalactin they will become queens with reduced levels of DNA methylation

Question 33

(transcriptional control) epigenetics- give an example of genetic imprinting (genetic factor that can be passed on)?

Answer 33

Angelman syndrome maternal copies are missing or inactive and paternal copies are silenced resulting in learning difficulties and growth abnormalities