The central dogma

Question 1

what is gene expression

Answer 1

process by which information from a gene is used in the making of a functional gene product

Question 2

what is transcription

Answer 2

process of making an RNA molecule complementary to a portion of a strand of DNA

Question 3

what is a promotor and transcription unit

Answer 3

a TATA box located in front of the transcription start point

Question 4

what are the steps of trancription

Answer 4

initiation, elongation, termination

Question 5

what happens in initiation

Answer 5

transcription factor proteins bind to the promoter in the area of the TATA box and an RNA polymerase forming the transcription initiation complex

Question 6

what happens in elongation

Answer 6

the DNA is copied to make RNA in complementary base pairs AU-GC

Question 7

Elongation: how does a transcription bubble happen

Answer 7

as the RNA polymerase slides along the transcription unit separates the DNA strand creating a bubble

Question 8

elongation: in what direction is DNA transcribed

Answer 8

5’ to 3’
transcribed antiparallel as well

Question 9

what is different in the ribonuceloside triphosphate from RNA to DNA

Answer 9

RNA has a OH attached to the 2’ carbon instead of DNA’s H

Question 10

elongation: what happens once the RNA polymerase has done its job

Answer 10

the DNA returns to it’s double helix

Question 11

how does the RNA polymerase know when to stop transcribing

Answer 11

it hits a sequence of nucleotides that signal the stop of transcription

Question 12

what is a codon

Answer 12

3 nucleotides in a row (sequence) on the mRNA (from transcription)

Question 13

why are there more than one codon that give the same amino acid

Answer 13

so that in the unlikely case a mistake is made we still get the right amino acid to make the right protein

Question 14

what is pre-mRNA

Answer 14

mRNA that is directly transcribed in the nucleus

Question 15

what is mature mRNA

Answer 15

mRNA that has gone through processing

Question 16

what makes an mRNA strand mature

Answer 16

a guanine cap, a poly(A) tail, removal of introns

Question 17

what is a guanine cap and why is it important

Answer 17

G cap added to the 5’ end of a pre-mRNA that protects mRNA’s from being degraded by the cytosol, facilitates transport from the nucleus, the site where the ribosome attach in translation

Question 18

what is a poly(A) tail and why is it important

Answer 18

an added 50-250 adenine nucleotides to the 3’ end of pre-mRNA
allows for export through the membrane, makes translation of mRNA into amino acids and proteins easier, and the longer the tail the more times mRNA can be translated before degradation

Question 19

how does it know when to add the poly(A) tail

Answer 19

a polyadenylation signal

Question 20

what are introns

Answer 20

non-coding sequences mixed with exons (coding sequences)
need to be removed so we are only left with coding exons in the mature mRNA

Question 21

what is tRNA

Answer 21

transfer RNA, serves as code readers

Question 22

what does tRNA carry

Answer 22

an amino acid and anticodons

Question 23

what are anticodons

Answer 23

a sequence of three nucleotides forming a unit of genetic code in a transfer RNA molecule, corresponding to a complementary codon in messenger RNA

Question 24

how do we add amino acids to tRNA

Answer 24

through aminoacyl-tRNA synthetase enzyme in the cytosol that add the correct amino acid onto the tRNA with the correct anticodon

Question 25

stages of translation

Answer 25

initiation, elongation, termiantion

Question 26

what happens in the beginning of initiation in translation

Answer 26

we bind together an initiator tRNA with amino acid methionine (the singular start codon), the mRNA, and the small ribosomal subunit

Question 27

why is it important that the initiator tRNA connects to the correct sequence of mRNA

Answer 27

establishes how it reads to codons in the right way gets the right amino acids

Question 28

what happens at the end of initiation in translation

Answer 28

the large ribosomal subunit binds to the small subunit creating three sites to accommodate tRNA's

Question 29

what are the three sites created for tRNA's in translation

Answer 29

E- exit site P- peptidyl site A- aminoacyl site

Question 30

what happens at the beginning of the elongation cycle in translation

Answer 30

tRNA attaches to the correct mRNA sequence (anticodon-codon) in the P site

Question 31

what happens after a tRNA is in the P site

Answer 31

a new tRNA carryign another amino acid attaches to teh A site and peptidyl transferase occurs

Question 32

what is peptidyl transferase

Answer 32

cataclyzes the formation of a peptide bond between amino acids held in the P and A sites

Question 33

what happens after peptidyl transferase in translation

Answer 33

the tRNA's shift to the next section the one in P moves to E to exit, one in A moves to P, and a new tRNA moves into A

Question 34

how is termination carried out

Answer 34

a stop codon in the mRNA and translation is terminated

Question 35

how are the polypeptide chains released in termination (translation)

Answer 35

since there is no tRNA with an anticodon complementary to the stop codons it is recognized by the release factor proteins

Question 36

what is the release factor proteins

Answer 36

something that binds to the stop codon and stimulates the release of the polypeptide chain from the ribosomal unit

Question 37

what is a polysome

Answer 37

when an mRNA strand has multiple ribosome working along it creating the same polypeptide

Question 38

can a functional protein be made up of more than one polypeptide and what happens to the expressed genes

Answer 38

yes, it can be made of 1 or more polypeptides, the more polypeptides the more genes are expressed

Question 39

what is post-translational modification of proteins

Answer 39

when after they exit the ribosome they are somehow folded or modified (add another, fold, etc.)

Question 40

what is the definition of a gene

Answer 40

a unit of heredity on a chromosome that contains the code for a protein molecule or the code for the functioning RNA molecules (tRNA, rRNA)

Question 41

what is a mutation

Answer 41

a permanent heritable change in the genetic material on the large or small scale

Question 42

what is a point mutation

Answer 42

where the mutation only affects one base pair of the DNA

Question 43

what are four types of point mutations

Answer 43

missense, nonsense, silent, and frameshift mutations

Question 44

what is a missense mutation

Answer 44

change in the DNA sequence causing a change in the sense codon (that specifies the amino acid needed) producing a different amino acid changing the function of the protein

Question 45

what is a nonsense mutation

Answer 45

a change in the DNA sequence that causes a change in the nonsense (stop) codon making a shorter polypeptide chain Very unlikely the polypeptide will be functional

Question 46

what is a silent mutation

Answer 46

Change in the DNA sequence causes a change of a codon to a different sense codon but the new codon specifies the same amino acid as in the normal polypeptide Function is unchanged

Question 47

what is a frameshift mutation

Answer 47

Deletion or insertion in the DNA sequence that causes a change in the reading frame of the resulting mRNA After the mutation point will produce a different amino acid sequence resulting in a non-functional polypeptide