Genes and Proteins Flashcards

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1
Q

7-methylguanosine cap

A

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

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2
Q

Aminoacyl tRNA synthetase

A

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

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3
Q

Anticodon

A

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

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4
Q

CAAT box

A

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

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5
Q

Central dogma

A

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

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6
Q

Codon

A

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

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7
Q

Colinear

A

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

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8
Q

Consensus

A

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

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9
Q

Core enzyme

A

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

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10
Q

Degeneracy

A

(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

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11
Q

Downstream

A

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

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12
Q

Exon

A

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

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13
Q

FACT

A

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

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14
Q

GC-rich box

A

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

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15
Q

Hairpin

A

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

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16
Q

Holoenzyme

A

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

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17
Q

Initiation site

A

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

18
Q

Initiator tRNA

A

in prokaryotes, called tRNAMetf
; 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

19
Q

Intron

A

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

20
Q

Kozak’s rules

A

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

21
Q

Nonsense codon

A

one of the three mRNA codons that specifies termination of translation

22
Q

Nontemplate strand

A

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

23
Q

Octamer box

A

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

24
Q

Peptidyl transferase

A

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

25
Q

Plasmid

A

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

26
Q

Poly-A tail

A

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

27
Q

Polysome

A

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

28
Q

Preinitiation complex

A

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

29
Q

Promoter

A

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

30
Q

Reading frame

A

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

31
Q

rho-dependent termination

A

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

32
Q

rho-independent

A

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

33
Q

RNA editing

A

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

34
Q

Shine-Dalgarno sequence

A

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

35
Q

Signal sequence

A

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

36
Q

Small nuclear RNA

A

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

37
Q

Splicing

A

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

38
Q

Start codon

A

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

39
Q

TATA box

A

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

40
Q

Template strand

A

strand of DNA that specifies the complementary mRNA molecule

41
Q

Transcription bubble

A

region of locally unwound DNA that allows for transcription of mRNA

42
Q

upstream

A

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