Ch 7: RNA and the Genetic Code

Question 1

Central Dogma

Answer 1

DNA -> RNA -> proteins

Question 2

degenerate code allows

Answer 2

multiple codons to encode for the same amino acid

Question 3

Initiation (start) codon

Answer 3

AUG

Question 4

Termination (stop) codon

Answer 4

UGA, UAA, UAG

Question 5

redundancy and wobble (third base codon) allows

Answer 5

mutations to occur without effects in the protein

Question 6

point mutations can cause

Answer 6

silent, nonsense (truncation), missense

Question 7

silent mutations

Answer 7

with no effect on protein synthesis

Question 8

nonsense (truncation) mutations

Answer 8

produce a premature stop codon

Question 9

missense mutations

Answer 9

produce a codon that codes for a different amino acid

Question 10

frameshift mutations

Answer 10

result from nucleotide addition or deletion, and change the reading frame of subsequent codons

Question 11

RNA is structurally similar to DNA except

Answer 11

substitution of a ribose sugar for deoxyribose
substitution of uracil for thymine
single-stranded instead of double-stranded

Question 12

3 types of RNA with separate jobs during transcription

Answer 12

messenger, transfer, and ribosomal

Question 13

messenger RNA (mRNA)

Answer 13

carries the message from DNA in the nucleus via transcription of the gene; travels into the cytoplasm to be translated

Question 14

transfer RNA (tRNA)

Answer 14

brings in amino acids, recognizes the codon on the mRNA using its anticodon

Question 15

Ribosomal RNA (rRNA)

Answer 15

makes up the ribosome; enzymatically active

Question 16

unwind the DNA double helix

Answer 16

helicase and topoisomerase

Question 17

RNA polymerase II

Answer 17

binds to the TATA box within the promoter region the gene (25 bp upstream from first transcribed base)

Question 18

hnRNA is synthesized from

Answer 18

DNA template (Antisense) strand

Question 19

posttranscriptional modifications include

Answer 19

7-methylguanylate triphosphate cap added to the 5’ end

polyadenosyl (poly-A) tail is added to the 3’ end

Question 20

Spicing is done by ___ and ____ in the ___ ; introns are removed in the ___ structure, and exons are ligated together

Answer 20

snRNA
snRNPs
lariat

Question 21

polycistronic genes

Answer 21

allows prokaryotic cells to increase their variability of gene products from one transcript through this; starting transcription in different sites the gene leads to different gene products

Question 22

alternative splicing

Answer 22

how eukaryotic cells increase variability of gene products ; by combining different exons in a modular fashion to acquire different gene products

Question 23

translates the codon into the correct amino acid

Answer 23

tRNA

Question 24

factories where translation (protein synthesis) occurs

Answer 24

ribosomes

Question 25

3 stages of translation are

Answer 25

initiation, elongation, and termination

Question 26

Initiation in prokaryotes

Answer 26

occurs when the 30S ribosome attaches to the Shine-Dalgarno sequence and scans for a start codon; it lays down N-formylmethionine in the P site of the ribosome

Question 27

Initiation is eukaryotes

Answer 27

occues when the 40S ribosome attaches to the 5’-cap and scans for a start codon; it lays down methionine on the P site of the ribosome

Question 28

Elongation involves the addition of

Answer 28

a new aminoacyl-tRNA into the A site of the ribosome and transfer of the growing polypeptide chain from the tRNA in the P site to the tRNA in the A site. The now uncharged tRNA pauses in the E site before exiting the ribosome

Question 29

Termination occurs when the codon in the

Answer 29

A site is a stop codon, release factor places a water molecule on the polypeptide chain and thus releases the protein

Question 30

help with each step in the recruitment and assembly/disassembly of the ribosome

Answer 30

initiation, elongation, and release factor

Question 31

posttranslational modifications include

Answer 31

folding by chaperones
formation of quaternary structure
cleavage of proteins or single sequence
covalent addition of other biomolecules (phosphorylation, carboxylation, glycosylation, prenylation)

Question 32

Jacob-Monad model explains

Answer 32

how operons work with repressors and activators

Question 33

operons

Answer 33

are inducible or repressible clusters of genes transcribed as a single mRNA

Question 34

inducible systems

Answer 34

bound by a repressor under normal conditions; they can be turned on by an inducer pulling the repressor from the operator site

lac operon

Question 35

repressible systems

Answer 35

transcribed under normal conditions; they can be turned off by a corepressor coupling with the repressor from the operator site

trp operon

Question 36

search for promoter and enhancer regions in the DNA

Answer 36

transcriptional factors (promoters, enhancers)

Question 37

within 25 base pairs of the transcription start site

Answer 37

promoter

Question 38

more than 25 bp away from the transcription start site

Answer 38

enhancers

Question 39

modifications of _____ affects the ability of transcriptional enzymes to access the DNA through ___ or ___

Answer 39

chromatin structure

histone acetylation (increases accesibility)
DNA methylation (decreases accessibility)