gene regulation

Question 1

how do prokaryotes regulate the production of enzymes?

Answer 1

feedback inhibition or gene regulation

Question 2

what is a mechanism for control of gene expression in bacteria?

Answer 2

the operon model

Question 3

3 points about trp ?

Answer 3

cluster of functionally related genes which can be on or off
switch called an operator positioned with a primer
operon switched off by repressor enzyme

Question 4

what does a repressor enzyme do to trp operon?

Answer 4

prevents gene transcription by binding to operator and blocks rna polymerase

Question 5

what is a corepressor?

Answer 5

cooperates a repressor to switch operon off

Question 6

what does a lac operon do?

Answer 6

hydrolyse lactose
if lactose present, a side product binds to repressor activating it and so can no longer bind so enzymes are produced for hyrolysing lactose = glucose

Question 7

what is an inducible enzyme?

Answer 7

usually function in catabolic pathways; synthesis induced by chem signal

Question 8

what is a repressible enzyme?

Answer 8

function in anabolic pathways

Question 9

what is positive gene regulation?

Answer 9

when lactose is present , glucose is scarce (cAMP level high)

Question 10

what is an operon composed of?

Answer 10

a promoter / operator and genes (upstream regulatory genes)

Question 11

what are the two types of operons?

Answer 11

repressible trp, inducible lac

Question 12

what is chromatin?

Answer 12

a complex of proteins and nucleic acid in nuclei

Question 13

what is NCP?

Answer 13

nucleosome core particle

Question 14

which genes are not expressed?

Answer 14

genes with highly packed heterochromatin

Question 15

what is epigenetic inheritance?

Answer 15

although chromatin modifications do not alter DNA they can be passed down generations

Question 16

what is a chromosome territory?

Answer 16

chromosome capture techniques allow identification of regions of chromosomes which interact

Question 17

two parts of nuclear architecture?

Answer 17

loop of chromatin and transcription factories

Question 18

post transcriptional mechanisms do?

Answer 18

allow a cell to fine tune gene expression rapidly

include RNA processing and RNA degredation

Question 19

what are three mechanisms of RNA processing?

Answer 19

adding 5’ cap, adding ploy-a tail, removing introns

Question 20

4 points about mRNA degredation?

Answer 20

lifespan is important
eukaryotic mrna lives longer than prokaryotic
nucleotide sequences influence lifespan
longer the lifespan, more protein made

Question 21

what processing do polypeptides undergo?

Answer 21

cleavage and chemical modifications

Question 22

what is length of protein functions regulated by?

Answer 22

selective degradation

Question 23

what marks proteins for degradation?

Answer 23

ubiquitin

Question 24

what degrades proteins?

Answer 24

proteasome

Question 25

what are microRNA?

Answer 25

small single stranded RNA that bind to complementary sequences in mRNA
can cause degradation pf traget mRNA or sometimes block translation

Question 26

what are siRNA?

Answer 26

small and similar to microrna , block gene expression by siRNA called rna interference

Question 27

what effects do piRNA have on chromatin?

Answer 27

small ncRNA induce formation of heterochromatin blocking expression of parasitic DNA in genome known as transposons