15: Genes and Proteins

Question 1

modification added to the 5’ end of pre mRNAs to protect mRNA from degradation and assist translation

Answer 1

7-methylguanosine cap

Question 2

enzyme that “charges” tRNA molecules by catalyzing a bond between the tRNA and a corresponding amino acid

Answer 2

aminoacyl tRNA synthetase

Question 3

three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon

Answer 3

anticodon

Question 4

(GGCCAATCT) essential eukaryotic promoter sequence involved in binding transcription factors

Answer 4

CAAT box

Question 5

states that genes specify the sequence of mRNAs, which in turn specify the sequence of proteins

Answer 5

central dogma

Question 6

three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation

Answer 6

codon

Question 7

in terms of RNA and protein, three “units” of RNA (nucleotides) specify one “unit” of protein (amino acid) in a consecutive fashion

Answer 7

colinear

Question 8

DNA sequence that is used by many species to perform the same or similar functions

Answer 8

consensus

Question 9

prokaryotic RNA polymerase consisting of α, α, β, and β’ but missing σ; this complex performs elongation

Answer 9

core enzyme

Question 10

(of the genetic code) describes that a given amino acid can be encoded by more than one nucleotide triplet; the code is degenerate, but not ambiguous

Answer 10

degeneracy

Question 11

nucleotides following the initiation site in the direction of mRNA transcription; in general, sequences that are toward the 3’ end relative to a site on the mRNA

Answer 11

downstream

Question 12

sequence present in protein-coding mRNA after completion of pre-mRNA splicing

Answer 12

exon

Question 13

complex that “facilitates chromatin transcription” by disassembling nucleosomes ahead of a transcribing RNA polymerase II and reassembling them after the polymerase passes by

Answer 13

FACT

Question 14

(GGCG) nonessential eukaryotic promoter sequence that binds cellular factors to increase the efficiency of transcription; may be present several times in a promoter

Answer 14

GC-rich box

Question 15

structure of RNA when it folds back on itself and forms intramolecular hydrogen bonds between complementary nucleotides

Answer 15

hairpin

Question 16

prokaryotic RNA polymerase consisting of α, α, β, β’, and σ; this complex is responsible for transcription initiation

Answer 16

holoenzyme

Question 17

nucleotide from which mRNA synthesis proceeds in the 5’ to 3’ direction; denoted with a “+1”

Answer 17

initiation site

Question 18

in prokaryotes, called ; in eukaryotes, called tRNAi; a tRNA that interacts with a start codon, binds directly to the ribosome P site, and links to a special methionine to begin a polypeptide chain

Answer 18

initiator tRNA

Question 19

non–protein-coding intervening sequences that are spliced from mRNA during processing

Answer 19

intron

Question 20

determines the correct initiation AUG in a eukaryotic mRNA; the following consensus sequence must appear around the AUG: 5’-GCC(purine)CCAUGG-3’; the bolded bases are most important

Answer 20

Kozak’s rules

Question 21

one of the three mRNA codons that specifies termination of translation

Answer 21

nonsense codon

Question 22

strand of DNA that is not used to transcribe mRNA; this strand is identical to the mRNA except that T nucleotides in the DNA are replaced by U nucleotides in the mRNA

Answer 22

nontemplate strand

Question 23

(ATTTGCAT) nonessential eukaryotic promoter sequence that binds cellular factors to increase the efficiency of transcription; may be present several times in a promoter

Answer 23

Octamer box

Question 24

RNA-based enzyme that is integrated into the 50S ribosomal subunit and catalyzes the formation of peptide bonds

Answer 24

peptidyl transferase

Question 25

extrachromosomal, covalently closed, circular DNA molecule that may only contain one or a few genes; common in prokaryotes

Answer 25

plasmid

Question 26

modification added to the 3' end of pre mRNAs to protect mRNA from degradation and assist mRNA export from the nucleus

Answer 26

poly-A tail

Question 27

mRNA molecule simultaneously being translated by many ribosomes all going in the same direction

Answer 27

polysome

Question 28

cluster of transcription factors and other proteins that recruit RNA polymerase II for transcription of a DNA template

Answer 28

preinitiation complex

Question 29

DNA sequence to which RNA polymerase and associated factors bind and initiate transcription

Answer 29

promoter

Question 30

sequence of triplet codons in mRNA that specify a particular protein; a ribosome shift of one or two nucleotides in either direction completely abolishes synthesis of that protein

Answer 30

reading frame

Question 31

in prokaryotes, termination of transcription by an interaction between RNA polymerase and the rho protein at a run of G nucleotides on the DNA template

Answer 31

rho-dependent termination

Question 32

termination sequence-dependent termination of prokaryotic mRNA synthesis; caused by hairpin formation in the mRNA that stalls the polymerase

Answer 32

rho-independent

Question 33

direct alteration of one or more nucleotides in an mRNA that has already been synthesized

Answer 33

RNA editing

Question 34

(AGGAGG); initiates prokaryotic translation by interacting with rRNA molecules comprising the 30S ribosome

Answer 34

Shine-Dalgarno sequence

Question 35

short tail of amino acids that directs a protein to a specific cellular compartment

Answer 35

signal sequence

Question 36

molecules synthesized by RNA polymerase III that have a variety of functions, including splicing pre-mRNAs and regulating transcription factors

Answer 36

small nuclear RNA

Question 37

process of removing introns and reconnecting exons in a pre-mRNA

Answer 37

splicing

Question 38

AUG (or rarely, GUG) on an mRNA from which translation begins; always specifies methionine

Answer 38

start codon

Question 39

conserved promoter sequence in eukaryotes and prokaryotes that helps to establish the initiation site for transcription

Answer 39

TATA box

Question 40

strand of DNA that specifies the complementary mRNA molecule

Answer 40

template strand

Question 41

region of locally unwound DNA that allows for transcription of mRNA

Answer 41

transcription bubble

Question 42

nucleotides preceding the initiation site; in general, sequences toward the 5' end relative to a site on the mRNA

Answer 42

upstream