cellular control🐛

Question 1

effect of insertion mutation

Answer 1

• reading frame shifts by one base (frameshift)
• alters triplet codes for amino acids
• amino acid sequence from point of frameshift will be different

Question 2

in the lac operon describe how Z and Y genes are controlled in the absence of lactose

Answer 2

• regulatory gene produces repressor protein
• repressor protein binds to operator
• RNA polymerase cannot move to promoter
• genes Z and Y not expressed

Question 3

what is the advantage of the lac operon being controlled by presence of lactose

Answer 3

• organism saved energy by only producing lactase in presence of lactose
• lactase produces when only lactose is available as a respiratory substrate

Question 4

what is a homeobox gene

Answer 4

• homeotic or regulatory gene that contains a homeobox sequence
• controls development of body plan

Question 5

how does a homeobox gene carry out its function

Answer 5

• homeobox gene codes for transcription factor
• TF binds to DNA with homeodomain
• TF controls expression of other genes by switiching them on and off

Question 6

what does highly conserved across species mean

Answer 6

homeobox genes in all species have very similar gene sequence and are located in the same positions

Question 7

suggest why homeobox genes have not really been changed by mutation

Answer 7

• mutation in homeobox genes likely to affect body plan or affect many other genes
• likely to be selected against

Question 8

outline apoptosis

Answer 8

• enzymes break down cytoskeleton
• nucleus breaks down
• bulges/blebs appear in plasma membrane
• cell breaks down into vesicles

Question 9

describe plant cloning

Answer 9

• cutting from parent plant
• dip in plant hormones
• put into pot where it grows into genetically identical plant

Question 10

advantages of plant cloning

Answer 10

• greater yield as all plants are desirable
• pest resistant so no pesticide needed
• faster to produce

Question 11

disadvantages of plant cloning

Answer 11

• less able to adapt to climate change
• more susceptible to same disease
• decreases biodiversity

Question 12

types of substitution mutation

Answer 12

• silent
• missense (changes one amino acid)
• nonsense (causes premature stop codon)

Question 13

what are the 3 regulatory mechanisms

Answer 13

• transcriptional level
• post transcriptional level
• post translational level

Question 14

what are regulatory mechanisms for

Answer 14

• not all genes expressed in all cells
• not all genes expressed all the time
• regulatory mechanisms ensure correct genes are expressed

Question 15

what is an operon

Answer 15

• group of genes controlled by same promoter
• under same regulatory mechanism
• transcribed together

Question 16

function of promoter

Answer 16

RNA polymerase binds to begin transcription

Question 17

what do the genes in the lac operon code for

Answer 17

lacZ= lactase
lacY= permease
lacA= transacetylase

Question 18

how to find out what genes are being expressed in a cell

Answer 18

analyse RNA is present as this shows which genes are transcribed

Question 19

where do transcription factors bind

Answer 19

promoter

Question 20

how are gene expressions regulated post translation

Answer 20

• protein modified by golgi apparatus
• activation by cAMP
• binding of cAMP alters shape of protein

Question 21

post transcription regulation

Answer 21

introns removed from mRNA by splicing to produce mature mRNA

Question 22

what are homeobox genes

Answer 22

• regulatory genes
• controls development of body plan
• by regulating mitosis and apoptosis
• code for homeodomain

Question 23

what is homeodomain

Answer 23

• transcription factor

- binds to DNA to regulate transcription

Question 24

what is a hox gene

Answer 24

-homeobox gene in animals

Question 25

what organisms have homeobox genes

Answer 25

highly conserved in plants, animals, fungi

Question 26

how does apoptosis control growth

Answer 26

cells produced earlier in development may no longer be needed

Question 27

what do tumour suppressor genes do

Answer 27

reduce cell division or stimulate apoptosis

Question 28

what do genes that control the cell cycle and apoptosis respond to

Answer 28

• internal stimuli: irreparable DNA damage, RNA decay, biochemical changes, can initiate apoptosis in stressed cells
• external stimuli: presence of signalling molecules eg cytokines hormones growth factors, pathogens pollutants and UV may damage cells faster than they are replaced

Question 29

explain how failure of the control mechanism by hox gene could lead to deformities

Answer 29

• transcription factor not activated
• gene expressed which should not have been
• molecules signalling apoptosis not produced
• if apoptosis does not occur, deformities can form

Question 30

explain how a mutation could alter a protein so that it no longer performs its function

Answer 30

• if frame shift then all triplets downstream will be different
• different tertiary structure so different shape

Question 31

where do transcription factors bind

Answer 31

promoter

Question 32

how is it possible for a mutation to have no effect on protein

Answer 32

• genetic code is degenerate so many combinations of triplets may code for same amino acid
• amino acid sequence not altered
• shape not altered