Kapitel 6

Question 1

Enzyme that attaches the correct amino acid to a tRNA molecule to form an aminoacyl-tRNA. (Figure 6–54)

Answer 1

aminoacyl-tRNA synthetase

Question 2

Sequence of three nucleotides in a transfer RNA (tRNA) molecule that is complementary to a three-nucleotide codon in a messenger RNA (mRNA) molecule.

Answer 2

anticodon

Question 3

Sequence of three nucleotides in a DNA or mRNA molecule that represents the instruction for incorporation of a specific amino acid into a growing polypeptide chain.

Answer 3

codon

Question 4

A summary or “average” of a large number of individual nucleotide sequences derived by comparing many sequences with the same basic function and tallying up the most common nucleotides found at each position. (Figure 6–12)

Answer 4

consensus nucleotide sequence

Question 5

Average or most typical form of a sequence that is reproduced with minor variations in a group of related DNA - RNA - or protein sequences. Indicates the nucleotide or amino acid most often found at each position. Preservation of a sequence implies that it is functionally important.

Answer 5

consensus sequence

Question 6

A conformation with loops or coils that DNA adopts in response to superhelical tension; conversely - creating various loops or coils in the helix can create such tension.

Answer 6

DNA supercoiling

Question 7

Protein that helps load initiator tRNA on to the ribosome - thus initiating translation.

Answer 7

eukaryotic initiation factor (eIF)

Question 8

Large protein complex with an interior rich in 3′-to-5′ RNA exonucleases; degrades RNA molecules to produce ribonucleotides.

Answer 8

exosome

Question 9

Any of the proteins whose assembly at all promoters of a given type is required for the binding and activation of RNA polymerase and the initiation of transcription. (Table 6–3 - p. 311)

Answer 9

general transcription factor

Question 10

The set of rules specifying the correspondence between nucleotide triplets (codons) in DNA or RNA and amino acids in proteins. (Figure 6–48)

Answer 10

genetic code

Question 11

A principle for increasing the specificity of substrate recognition by proteins and RNAs. In protein synthesis - a ribosome - or enzyme folds around a codon–anticodon interaction and only when the match is correct is the subsequent reaction allowed to proceed.

Answer 11

induced fit

Question 12

Special tRNA that intiates translation. It always carries the amino acid methionine - forming the complex Met-tRNAi. (Figure 6–70)

Answer 12

initiator tRNA

Question 13

A principle for increasing the specificity of catalysis. In the synthesis of DNA - RNA - and proteins - it refers to a time delay that begins with an irreversible step (such as ATP or GTP hydrolysis) and during which incorrect base pairs are more likely to dissociate than correct pairs.

Answer 13

kinetic proofreading

Question 14

RNA molecule that specifies the amino acid sequence of a protein. Produced in eukaryotes by processing of an RNA molecule made by RNA polymerase. It is translated into protein in a process catalyzed by ribosomes.

Answer 14

messenger RNA (mRNA)

Question 15

Protein that helps guide the proper folding of other proteins - or helps them avoid misfolding. Includes heat-shock proteins (hsp).

Answer 15

molecular chaperone (chaperone)

Question 16

An RNA molecule that is the final product of a gene and does not code for protein. These RNAs serve as enzymatic - structural - and regulatory components for a wide variety of processes in the cell.

Answer 16

noncoding RNA

Question 17

Mechanism for degrading aberrant mRNAs containing in-frame internal stop codons before they can be translated into protein. (Figure 6–76)

Answer 17

nonsense-mediated mRNA decay

Question 18

Large multiprotein structure forming an aqueous channel (the nuclear pore) through the nuclear envelope that allows selected molecules to move between nucleus and cytoplasm. (Figure 12–8)

Answer 18

nuclear pore complex (NPC)

Question 19

Nucleotide sequence in DNA to which RNA polymerase binds to begin transcription. (Figure 7–44)

Answer 19

promoter

Question 20

Nucleotide sequence in DNA to which RNA polymerase binds to begin transcription. (Figure 7–17)

Answer 20

promoter

Question 21

Large protein complex in the cytosol with proteolytic activity that is responsible for degrading proteins that have been marked for destruction by ubiquitylation or by some other means. (Figures 6–83 and 6–84)

Answer 21

proteasome

Question 22

The phase in which nucleotides are read in sets of three to encode a protein. An mRNA molecule can be read in any one of three reading frames - only one of which will give the required protein. (Figure 6–49)

Answer 22

reading frame

Question 23

Any one of a number of specific RNA molecules that form part of the structure of a ribosome and participate in the synthesis of proteins. Often distinguished by their sedimentation coefficient (e.g. - 28S rRNA - 5S rRNA).

Answer 23

ribosomal RNA (rRNA)

Question 24

Particle composed of rRNAs and ribosomal proteins that catalyzes the synthesis of protein using information provided by mRNA. (Figure 6–64)

Answer 24

ribosome

Question 25

Enzyme that catalyzes the synthesis of an RNA molecule on a DNA template from ribonucleoside triphosphate precursors. (Figure 6–9)

Answer 25

RNA polymerase

Question 26

Process in which intron sequences are excised from RNA transcripts. A major process in the nucleus of eukaryotic cells leading to formation of messenger RNAs (mRNAs).

Answer 26

RNA splicing

Question 27

Hypothesis that early life on Earth was based primarily on RNA molecules that both stored genetic information and catalyzed biochemical reactions.

Answer 27

RNA world

Question 28

Gene that specifies a ribosomal RNA (rRNA).

Answer 28

rRNA gene

Question 29

Small RNA molecules that are complexed with proteins to form the ribonucleoprotein particles (snRNPs) involved in RNA splicing. (Figures 6–28 and 6–29)

Answer 29

small nuclear RNA (snRNA)

Question 30

Small RNAs found in the nucleolus - with various functions - including guiding the modifications of precursor rRNA. (Table 6–1 - p. 305 - and Figure 6–41)

Answer 30

small nucleolar RNA (snoRNA)

Question 31

Large assembly of RNA and protein molecules that performs pre-mRNA splicing in eukaryotic cells.

Answer 31

spliceosome

Question 32

Sequence in the promoter region of many eukaryotic genes that binds a general transcription factor (TFIID) and hence specifies the position at which transcription is initiated. (Figure 6–14)

Answer 32

TATA box

Question 33

Signal in bacterial DNA that halts transcription; in eukaryotes - transcription terminates after cleavage and polyadenylation of the newly synthesized RNA.

Answer 33

terminator

Question 34

Set of small RNA molecules used in protein synthesis as an interface (adaptor) between mRNA and amino acids. Each type of tRNA molecule is covalently linked to a particular amino acid. (Figure 6–50)

Answer 34

transfer RNA (tRNA)