Gene expression

Question 1

what is the central dogma of molecular biology?

Answer 1

the information of cells in DNA which is transcripted into RNA and then translated into a protein

Question 2

what is transcription?

Answer 2

going from DNA to RNA

Question 3

what is translation?

Answer 3

going from RNA to polypeptide

Question 4

what is DNA?

Answer 4

a polymer molecule made up of a string of deoxyribonucleic acids - the sequence contains information to generate new organism

Question 5

what is the genome?

Answer 5

sequence of all the DNA in an organism (genes + non-coding regions)

Question 6

what is a gene?

Answer 6

unit of inheritance - many code for proteins but not all

Question 7

what are the three steps of transcription?

Answer 7

initiation, elongation and termination

Question 8

what is initiation?

Answer 8

RNA polymerase II to the start of the gene, DNA strands pulled apart

Question 9

what is elongation?

Answer 9

RNA gets longer - it forma a transcription bubble

Question 10

what is termination?

Answer 10

RNA synthesis stops

Question 11

what is RNA processing?

Answer 11

the primary RNA transcript (pre mRNA) includes introns
-processing in nucleus (5’ cap, 3’ PolyA tail, splicing by spliceosome.) now it is mRNA and is exported to cytoplasm for translation

Question 12

what are transcription factors?

Answer 12

proteins which bind to the short but very specific sequences of DNA. they affect the rate of transcription ( positively or negatively charged)

Question 13

how can transcription be initiated?

Answer 13

a transcription initiation complex is needed.
RNA polymerase II cannot bind directly to DNA
general or basal transcription factors act as a bridge

Question 14

what are some examples of transcription factors

Answer 14

-p53
-E2F
-oestrogen receptor
-testosterone receptor

Question 15

what are enhancers and silencers?

Answer 15

-DNA sequences where transcription factors bind to affect rate of transcription
-can be upstream or downstream of a gene
-can be close or very far away
-makes it more or less likely that a promotor is activated
-are required for expression of most genes
-major detriments of differential expression in space and time
-genes often have several enhancers, each bound by several TFs many signals determine level of expression of a gene

Question 16

how do we get open DNA ready for transcription?

Answer 16

surface enhancers, locus control regions. the open chromatin spanning several genes. an example is global genes

Question 16

how does Globin genes work?

Answer 16

transcription factors bind to globin LCR - only in erythrocytes, opens DNA of all global genes and gene expression is possible

Question 17

what is constitutive gene expression?

Answer 17

genes which are expressed in all cells at all time at about the same level. they maintain basic cell function (eg beta actin, ribosomal proteins)

Question 18

what is inducible gene expression?

Answer 18

genes which are only expressed in certain tissues or cells or only at certain times. they are called spatiotemporal gene expression. (eg cell specific - CD4, collagen. Time specific - cyclins, melatonin)

Question 19

what keeps DNA closed?

Answer 19

nucleosomes - keep it so tightly coiled around histones so transcription cannot occur.

Question 20

how do we open DNA?

Answer 20

super-enhancers called locus control regions

Question 21

what are locus control regions?

Answer 21

super enhancers. they are DNA sequences which can sometimes be quite far from the gene, where transcription factors can bind to make an area of DNA accessible to transcription factors.

Question 22

what is constitutive gene expression?

Answer 22

-genes which are expressed in all cells, all the time at about the same level
-they are housekeeping genes and maintain basic cell function
-they have a constitutive promoter, does not have many regulation points.

Question 23

what are some examples of constitutive genes?

Answer 23

-beta actin (microfilaments)
-ribosomal proteins
-general/basal transcription factors

Question 24

what is inducible gene expression?

Answer 24

-genes which are only expressed in certain tissues or cells -genes which are only produced at certain times

Question 25

what Is spatiotemporal gene expression?

Answer 25

specific to either space or time

Question 26

what are microRNA's

Answer 26

-a short RNA sequence -complementary binding to mRNA to initiate destruction of mRNA -can reduce gene expression post transcriptionally -involved in pathogenesis of cancer and other diseases

Question 27

what is the function of RNA polymerase?

Answer 27

to unwind the DNA double helix

Question 28

how can pre-mRNA be turned into mature mRNA?

Answer 28

5'capping polyadenylation splicing

Question 29

what is 5'capping?

Answer 29

the addition of a methylated guanine cap to the 5' end. its presence is vital for the recognition of the molecule by ribosomes and to protect the immature molecule from degradation by RNAases.

Question 30

what is polyadenylation?

Answer 30

the addition of a poly(A) tail to the 3' end of the mRNA. the poly(A) tail consists of multiple molecules of adenosine monophosphate. this helps to stabilise RNA which is necessary as RNA is much more unstable than DNA.

Question 31

where does translation occur?

Answer 31

cytoplasm

Question 32

what are tRNA molecules responsible for?

Answer 32

as they possess an anticodon which is complementary to the mRNA codon they are responsible for bringing the amino acids to the ribosome in the correct order, ready for the polypeptide assembly.

Question 33

what are aminoacyl-tRNA synthetases?

Answer 33

enzymes that link the amino acids to their corresponding tRNA molecules.

Question 34

what is the start codon specific to?

Answer 34

amino acid methionine which is nearly always the first amino acid in a polypeptide chain.