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BIO 111 > ch. 15 > Flashcards

ch. 15 Flashcards

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Biology 101 flashcards
1
Q

what is a 7-methylguanosine cap?

A

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

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2
Q

what is aminoacytl tRNA synthase?

A

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

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3
Q

what is an anticodon?

A

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

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4
Q

what is a CAAT box?

A

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

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5
Q

what is the central dogma?

A

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

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6
Q

what is a 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

what does colinear mean?

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

what is a consensus?

A

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

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9
Q

what is a 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

what is degeneracy of the genetic code?

A

it 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

what does downstream mean?

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

what is an exon?

A

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

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13
Q

what is a FACT complex?

A

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

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14
Q

what is a 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

what is a hairpin structure?

A

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

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16
Q

what is a 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

what is an information site?

A

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

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18
Q

what is initiator tRNA?

A

(in prokaryotes, called tRNA^Met f; 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

what is an intron?

A

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

20
Q

what are Kozak’s rules?

A

They determine the correct initiation Aug in a eukaryotic mRNA; the following consensus sequence must appear around the AUG; 5’-GCC(purine) CCAUGG-3’

21
Q

what is a nonsense codon?

A

one of the three mRNA codons that specifies termination of translation

22
Q

what is a nontemplate strand?

A

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

what is an Octamer box?

A

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

24
Q

what is peptidyl transferase?

A

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

25
Q

what are 50S ribosomal subunits?

A

50S is the larger subunit of the 70S ribosome of prokaryotes, i.e. bacteria and archaea. It is the site of inhibition for antibiotics.

26
Q

what is a plasmid?

A

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

27
Q

what is a poly-A tail?

A

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

28
Q

what is a polysome?

A

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

29
Q

what is a pre initiation complex?

A

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

30
Q

what is a promoter?

A

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

31
Q

what is a 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

32
Q

what is 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

33
Q

what is rho-independent termination?

A

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

34
Q

what is RNA editing?

A

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

35
Q

what is the Shine-Dalgarno sequence?

A

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

36
Q

what is a signal sequence?

A

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

37
Q

what are small nuclear RNA?

A

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

38
Q

what is splicing?

A

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

39
Q

what is the start codon?

A

AUG on an mRNA from which translation begins; always specifies methionine

40
Q

what is a TATA box?

A

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

41
Q

what is the template strand?

A

the strand of DNA that specifies the complementary mRNA molecule

42
Q

what is the transcription bubble?

A

the region of locally unwound DNA that allows for transcription of mRNA

43
Q

what does upstream mean?

A

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

BIO 111 (18 decks)

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