Chapter 16

Question 1

The immediate RNA product of transcription before any posttranscriptional processing reactions.

Answer 1

Primary Transcript

Question 2

A sequence of nucleotides in a gene that is transcribed but excised before the gene is translated. Also called an intervening sequence.

Answer 2

intron

Question 3

The segment of a eukaryotic gene that encodes a portion of the final product of the gene; a segment of RNA that remains after posttranscriptional processing and is transcribed into a protein or incorporated into the structure of an RNA.

Answer 3

exon

Question 4

A residue of 7-methylguanosine (7-meG) linked to the 5′-terminal residue of an mRNA through a 5′,5′-triphosphate linkage, which protects the mRNA from exoribonucleases.

Answer 4

5’ Cap

Question 5

A protein complex that recruits capped mRNAs to the ribosome to initiate translation.

Answer 5

cap-binding complex

Question 6

A length of adenosine residues (typically 80 to 250) added to the 3′ end of many mRNAs in eukaryotes (and sometimes in bacteria), which serves as a binding site for proteins that protect the mRNA from exonucleases.

Answer 6

3′ poly(A) tail

Question 7

The site where an mRNA is cleaved by a specific endonuclease to generate the free 3′ hydroxyl to which A residues are added. The site is marked by a highly conserved 5′-AAUAAA sequence 10 to 30 nucleotides on the 5′ side, and a G- and U-rich region 20 to 40 nucleotides on the 3′ side.

Answer 7

poly(A) addition site:

Question 8

The removal of introns and joining of exons in a primary transcript

Answer 8

RNA splicing

Question 9

A ribonucleoprotein complex that splices mRNAs in eukaryotic cells

Answer 9

spliceosome

Question 10

The splicing of exons from a single gene in various combinations to produce different mRNAs and thus different polypeptides.

Answer 10

alternative splicing

Question 11

The existence of more than one site in an mRNA that may be cleaved to generate the free 3′ hydroxyl to which A residues are added, which can generate diverse transcripts from a single gene.

Answer 11

poly(A) site choice

Question 12

An internal A residue just upstream of the 3′ splice site of an intron that attacks the phosphate at the 5′ splice site, forming the loop of the intron lariat.

Answer 12

branch point

Question 13

A protein and snRNA complex, found in the nucleus and a component of the spliceosome.

Answer 13

small nuclear ribonucleoprotein (snRNP):

Question 14

A class of short, noncoding RNAs, typically 100 to 200 nucleotides long, found in the nucleus and involved in the splicing of eukaryotic mRNAs.

Answer 14

small nuclear RNA (snRNA):

Question 15

A large, self-splicing ribozyme that catalyzes its own excision from an mRNA, tRNA, or rRNA transcript in a reaction that requires a guanosine nucleotide or nucleoside to initiate the reaction.

Answer 15

Group 1 Intron

Question 16

A large, self-splicing ribozyme that catalyzes its own excision from an mRNA transcript as a lariat structure.

Answer 16

Group 2 Intron

Question 17

A process in nematode worms in which a short leader sequence is spliced to the 5′ end of a primary transcript from a separate RNA molecule.

Answer 17

trans-splicing

Question 18

The posttranscriptional modification of an mRNA that alters one or more codons prior to translation.

Answer 18

RNA editing

Question 19

The enzymatic removal of amino groups from biomolecules such as amino acids or nucleotides.

Answer 19

deamination

Question 20

A protein complex that catalyzes the insertion or deletion of nucleotide residues during the process of RNA editing

Answer 20

editosome

Question 21

An enzyme that catalyzes the conversion of adenosine to inosine by removal of the amino group at C-6 on the adenine ring.

Answer 21

adenosine deaminase acting on RNA (ADAR):

Question 22

A family of nuclear transport receptors including importins and exportins

Answer 22

karyopherins

Question 23

A protein receptor responsible for transporting noncoding RNAs processed in the cytoplasm into the nucleus through a nuclear pore.

Answer 23

importin

Question 24

A protein receptor responsible for transporting RNAs from the nucleus, through a nuclear pore, into the cytoplasm.

Answer 24

exportin

Question 25

A molecular complex of RNA and protein, such as the ribosome.

Answer 25

ribonucleoprotein (RNP):

Question 26

A complex of proteins deposited on an mRNA by the spliceosome 20 to 24 nucleotides upstream of exon-exon junctions.

Answer 26

exon junction complex (EJC)

Question 27

The complete hydrolysis of RNA into its component ribonucleotides, usually catalyzed by ribonucleases or the exosome

Answer 27

RNA degradation

Question 28

A complex of 3′→5′ exonucleases in eukaryotic cells that processes the 3′ ends of rRNAs and tRNAs and is responsible for RNA degradation in higher eukaryotes.

Answer 28

exosome

Question 29

A pathway for degradation of mRNA molecules with a premature stop codon, triggered by the presence of an exon junction complex on a transcript that has been translated.

Answer 29

nonsense-mediated mRNA decay (NMD):

Question 30

An area in the cytoplasm of a eukaryotic cell where mRNAs that are not being translated are sequestered, possibly for degradation.

Answer 30

processing body (P body)

Question 31

The primary transcript of ribosomal RNAs in bacterial and eukaryotic cells, which is processed into mature ribosomal RNAs (and transfer RNAs in bacteria).

Answer 31

preribosomal RNA (pre-rRNA):

Question 32

A protein and snoRNA complex that guides the modification of rRNAs in the nucleolus

Answer 32

small nucleolar ribonucleoprotein (snoRNP):

Question 33

A class of short, noncoding RNAs, generally 60 to 300 nucleotides long, found in the nucleolus and involved in the modification of rRNAs.

Answer 33

small nucleolar RNA (snoRNA):

Question 34

A class of small RNA molecules (21 to 23 nucleotides after processing is complete) involved in gene silencing by inhibiting translation and/or promoting the degradation of particular mRNAs.

Answer 34

microRNA (miRNA)

Question 35

An endonuclease in eukaryotic cells that cleaves the hairpin of primary miRNA transcripts to produce pre-miRNAs.

Answer 35

Drosha

Question 36

An endonuclease in eukaryotic cells that catalyzes the hydrolysis of double-stranded RNAs, producing siRNAs or processing pre-miRNAs to mature miRNAs. Dicer also plays a role in the creation of RNA-induced silencing complexes.

Answer 36

Dicer: