6.1 Gene Expression Flashcards Preview

A Level Biology > 6.1 Gene Expression > Flashcards

Flashcards in 6.1 Gene Expression Deck (33):
1

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

housekeeping genes

2

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

tissue specific genes

3

how is expression of genes regulated?

switching genes on and off
increasing or decreasing the rate of product synthesis

4

bacteria respond to changes in environment by expressing genes when?

when products are required

5

what is gene regulation in multicellular organisms needed for?

cell specialisation

6

what levels are genes regulated at?

transcriptional
post transcriptional
translation
post translational

7

at transcriptional level what can happen to genes?

they can be turned on or off

8

at post transcriptional level what happens to mRNA?

it is modified regulating transcription and the types of protein produced

9

at translational level, what can happen to translation?

it can be stopped or started

10

at post translational level what can happen to proteins?

they can be modified after synthesis changing their functions

11

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

chromatin remodelling
histone modification
lac operon
cyclic AMP

12

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

epigenetics

13

(transcriptional control) what is chromatin?

DNA wound around histones in eukaryotic cells

14

(transcriptional control) what is heterochromatin?

tightly wound DNA visible during cell division

15

(transcriptional control) what is euchromatin?

loosely wound DNA during interphase so DNA can be replicated

16

(transcriptional control) why does DNA coil around histones?

histones are positively charged
DNA is negatively charged

17

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

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

18

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

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

19

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

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

20

(transcriptional control) what is an operon?

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

21

(transcriptional control) why is an operon efficient?

way of saving resources
if certain gene products aren't needed all genes switch off

22

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

located near the operon
codes for a repressor protein

23

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

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

24

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

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

25

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

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

26

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

bind to the promoter
transcribing the genes so the enzymes can be synthesised

27

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

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

28

(transcriptional control) what is epigenetics?

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

29

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

DNA methylation & histone modification

30

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

acetyl groups from histones
causing gene silencing making the DNA histone complex more tightly packed

31

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

gametes

32

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

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

33

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

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

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