Chapter 7

Question 1

Transcription

Answer 1

process in which RNA polymerase uses one strand of DNA as a template to synthesize a complementary RNA sequence

Question 2

RNA polymerase

Answer 2

enzyme that catalyzes the synthesis of an RNA molecule from a DNA template using ribonucleoside triphosphate precursors

Question 3

Do RNA polymerases need a primer?

Answer 3

no

Question 4

Do RNA polymerases proofread their work?

Answer 4

no

Question 5

messenger RNA (mRNA)

Answer 5

RNA molecule that specifies the amino acid sequence of a protein

Question 6

each mRNA carries information transcribed for _____

Answer 6

just one gene which codes for a single protein

Question 7

noncoding RNA

Answer 7

an RNA molecule that is the final product of a gene and does not code for protein
serve as enzymatic, structural, and regulatory components

Question 8

ribosomal RNAs form the _______ of the ribosomes

Answer 8

structural and catalytic core

Question 9

transfer RNAs (tRNAs)

Answer 9

act as adaptors that select specific amino acids and hold them in place as the ribosome links them to the growing protein

Question 10

microRNAs (miRNAs)

Answer 10

regulate gene expression

Question 11

small interfering RNAs (siRNAs)

Answer 11

provide protection from viruses and proliferating transposable elements

Question 12

long noncoding RNAs (lncRNAs)

Answer 12

act as scaffolds and serve other diverse function, many of which are still being discovered

Question 13

Promoter

Answer 13

DNA sequence that initiates gene transcription
includes sequences recognized by RNA polymerase and its accessory proteins

Question 14

what does the sigma factor do

Answer 14

begins to open the DNA double helix to examine the exposed base pairs

Question 15

which direction of DNA is used as its template

Answer 15

3’ to 5’ direction

Question 16

general transcription factors

Answer 16

proteins that assemble on the promoters of eukaryotic genes near the start site of transcription and load the RNA polymerase in the correct position

Question 17

RNA processing steps

Answer 17

capping
splicing
polyadenylation

Question 18

RNA capping

Answer 18

modification of the 5’ end of a maturing RNA transcript by the addition of an atypical nucleotide

Question 19

polyadenylation

Answer 19

the addition of multiple adenine nucleotides to the 3’ end of a newly synthesized mRNA molecule

Question 20

introns

Answer 20

noncoding sequence within a eukaryotic gene that is transcribed into an RNA molecule but is then excised by RNA splicing to produce an mRNA

Question 21

exon

Answer 21

segment of a eukaryotic gene that is transcribed into RNA and dictates the amino acid sequence of part of a protein

Question 22

RNA splicing

Answer 22

process in which intron sequences are excised from RNA molecules in the nucleus during the formation of a mature messenger RNA

Question 23

small nuclear RNA (snRNA)

Answer 23

RNA molecules that participate in RNA splicing

Question 24

spliceosome

Answer 24

large assembly of RNA and protein molecules that splices introns out of pre-mRNA in the nucleus of eukaryotic cells

Question 25

alternative splicing

Answer 25

production of different mRNAs from the same gene by splicing its RNA transcripts in different ways

Question 26

mRNA transport from the nucleus to the cytosol is _______ and is mediated by _______

Answer 26

highly selective nuclear pore complexes

Question 27

what is true of eukaryotic mRNAs? -they are synthesized and translated simultaneously -they must always be folded into a complex three-dimensional shape before they can be translated -they are subjected to processing only after being released by the polymerase -they are translated after they are exported from the nucleus

Answer 27

they are translated after they are exported from the nucleus

Question 28

a RNA chain is synthesized in which direction

Answer 28

5' to 3' only

Question 29

in eukaryotes, which parts of a gene are transcribed into RNA?

Answer 29

introns and exons

Question 30

translation

Answer 30

process by which the sequence of nucleotides in a messenger RNA molecule directs the incorporation of amino acids into protein

Question 31

codon

Answer 31

group of 3 consecutive nucleotides that specifies a particular amino acid or that starts or stops protein synthesis

Question 32

reading frames

Answer 32

one of three possible ways in which a set of successive nucleotide triplets can be translates into protein, depending on which nucleotide serves as the starting point

Question 33

transfer RNA (tRNA)

Answer 33

small RNA molecule that serves as an adaptor that "reads" a codon in mRNA and serves as the source of the amino acid added to the growing polypeptide chain

Question 34

anticodon

Answer 34

set of 3 consecutive nucleotides in a tRNA molecule that recognizes, through base-pairing, the 3 nucleotide codon on a mRNA molecule

Question 35

aminoacyl-tRNA synthetase

Answer 35

during protein synthesis, and enzyme that attaches the correct amino acid to a tRNA molecule to form a "charged" aminoacyl-tRNA

Question 36

_____ are responsible for the ribosome's overall structure and its ability to catalyze protein synthesis

Answer 36

rRNAs

Question 37

ribozymes

Answer 37

RNA molecules that possess catalytic activity

Question 38

initiator tRNA

Answer 38

special tRNA that initiates the translation of an mRNA on a ribosome always carries methionine

Question 39

translation initiation factor

Answer 39

protein that promotes the proper association of ribosomes with mRNA and is required for the initiation of protein synthesis

Question 40

start codon

Answer 40

AUG codes for methionine

Question 41

stop codons

Answer 41

UAA UAG UGA

Question 42

protease

Answer 42

enzyme that degrades proteins by hydrolyzing their peptide bonds

Question 43

proteasome

Answer 43

large protein machine that degrades proteins that are damaged, misfolded, or no longer needed by the cell

Question 44

ubiquitin

Answer 44

major role is to mark target proteins for degradation by the proteasome

Question 45

how many different aminoacyl-tRNA synthetases do most organisms have?

Answer 45

one for each amino acid

Question 46

what is false regarding codons in mRNA molecules -some codons do not code for amino acids -in some cases, several different codons code for the same amino acid -all codons contain three nucleotides -some codons code for more than one amino acid

Answer 46

some codons code for more than one amino acid

Question 47

which reaction is catalyzed by a ribozyme in present-day cells? -RNA polymerization during transcription in bacteria -DNA polymerization during DNA replication -peptide bond hydrolysis by the proteasome -peptide bond formation during translation

Answer 47

peptide bond formation during translation