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MCAT Biochemistry > Chapter 7: RNA and the Genetic Code > Flashcards

Chapter 7: RNA and the Genetic Code Flashcards

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MCAT flashcards
1
Q

DNA coding strand is identical to the ________.

A

mRNA

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2
Q

The DNA template strand is ________________ and ____________ to the mRNA.

A

complementary; antiparallel

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3
Q

____________ RNA carries information specifying the amino acid sequence of the protein to the ribosome.

A

messenger

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4
Q

mRNA may undergo a host of ________________ modifications prior to its release from the nucleus.

A

posttranscriptional

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5
Q

mRNA is transcribed from template DNA strands by ____ ____________ in the ________ of cells.

A

RNA polymerase; nucleus

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6
Q

mRNA is the only type of RNA that contains information that is translated into ________.

A

proteins

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7
Q

In eukaryotes, mRNA is ____________, meaning each mRNA molecule translates into only one protein product.

A

monocistronic

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8
Q

In prokaryotes, mRNA may be ____________, and starting the process of translation at different locations in the mRNA can result in different proteins.

A

polycistronic

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9
Q

____________ RNA is responsible for converting the language of nucleic acids to to the language of amino acids and peptides.

A

transfer

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10
Q

Each tRNA molecule contains a folded strand of RNA that includes a 3-nucleotide ____________.

A

anticodon

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11
Q

To become part of a nascent polypeptide in the ribosome, amino acids are connected to a specific tRNA molecule; such tRNA molecules are said to be ________ or ________ with an amino acid.

A

charged, actiavated

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12
Q

Each type of amino acid is activated by a different ____________-________ ____________ that requires 2 high-energy bonds from ____, implying that the attachment of the amino acid is an energy rich bond.

A

aminoacyl-tRNA synthetase; ATP

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13
Q

Aminoacyl-tRNA synthetase transfers the activated amino acid to the ____ end of the correct tRNA.

A

3’

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14
Q

Each tRNA has a ____ nucleotide sequence where the amino acid binds.

A

CCA

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15
Q

The high-energy aminoacyl-tRNA bond is used to supply the energy needed to create a ________ bond during translation.

A

peptide

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16
Q

____________ RNA is synthesized in the ________ and functions as an integral part of the ribosomal machinery used during protein assembly in the cytoplasm.

A

ribosomal; nucleolus

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17
Q

Many rRNA molecules function as ____________, that is, enzymes made of RNA molecules instead of peptides.

A

ribozymes

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18
Q

rRNA helps catalyze the formation of peptide bonds and is also important in splicing out its own ________ within the nucleus.

A

introns

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19
Q

Every preprocessed eukaryotic protein starts with the exact same amino acid: ________________.

A

methionine

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20
Q

The codon for methionine (____) is considered the ________ codon for tranlation of the mRNA into protein.

A

AUG; start

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21
Q

What are the 3 stop codons?

A

UAA, UGA, UAG

U Are Annoying, U Go Away, U Are Gone

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22
Q

The genetic code is ____________ because more than 1 codon can spcify a single amino acid.

A

degenerate

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23
Q

A ____________ mutation is where one amino acid substitutes for another.

A

missense

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24
Q

A ____________ mutation is where the codon now encodes for a premature stop codon.

A

nonsense

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25
Q

The creation of mRNA from DNA is ____________.

A

transcription

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26
Q

RNA polymerase locates genes by searching for specialized DNA regions known as ____________ regions.

A

promoter

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27
Q

In eukaryotes, ____ ____________ ____ is the main player in transcribing mRNA, and its binding site in the promoter region is known as the ________ ____.

A

RNA polymerase II; TATA box

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28
Q

____________ ________ help RNA polymerase locate and bind to this promoter region of the DNA, helping to establish where transcription will start.

A

Transcription factors

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29
Q

RNA polymerase does not require a ________ to gstart generating a transcript.

A

primer

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30
Q

RNA polymerase I is located in the ____________ and synthesizes ________.

A

nucleolus; rRNA

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31
Q

RNA polymerase III is located in the nucleus and synthesizes ________ and some ________.

A

tRNA and some rRNA

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32
Q

Does RNA polymerase proofread?

A

No!

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33
Q

RNA polymerase travels along the ____________ strand, and RNA is thus identical to the ________________ strand.

A

template, coding

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34
Q

The first base transcribed from DNA to RNA is defined as the ____ base of that gene region.

A

+1

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35
Q

Bases to the left of the first transcribed base (+1) are known as being ____________ and are given ____________ numbers.

A

upstream; negative

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36
Q

Bases to the right of the first transcribed base are ____________ and are given ____________ numbers.

A

downstream; positive

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37
Q

The TATA box usually falls around position ____.

A

-25

38
Q

After a stop sequence is reached, transcription is terminated, the DNA helix reforms, and the primary transcript formed is termed ________________ ____________ RNA (hnRNA).

A

heterogeneous nuclear

39
Q

Before hnRNA can leave the nucleus to be translated, it must undergo what 3 processes?

A
  1. intron/exon splicing
  2. addition of 5’ cap
  3. addition of 3’ poly-A tail
40
Q

Splicing removes noncoding sequences called ____________ and ligates coding sequences called ____________.

A

introns, exons

41
Q

Splicing is accomplished by the ________________.

A

spliceosome

42
Q

In the spliceosome, ________ ________ RNA molecules couple with proteins known as ________ ________ ________________.

A

small nuclear; small nuclear ribonucleoproteins

43
Q

At the 5’ end of the hnRNA molecule, a ____ is added during transcription. What does this do?

A

cap; it is recognized by the ribosome as the binding site and protects the mRNA from degrading in the cytoplasm

44
Q

A ________-____ tail is added to the ____ end of the mRNA transcript and protects the message against rapid degrdation.

A

poly-A, 3’

45
Q

As soon as the mRNA leaves the nucleus, it will start to ________ from the 3’ end. The longer the poly-A tail, the longer the mRNA can survive before this happens.

A

degrade

46
Q

When only exons remain and the cap and tail have been added, the cell has created the ________ mRNA.

A

mature

47
Q

____________ regions of the MRNA will still exist at the 5’ and 3’ edges of the transcript because the ribosome initiates translation at the start codon and will end at a s top codon.

A

untranslated

48
Q

For some genes, the primary transcript can be spliced together in different ways to produce different protein variants. This is called ____________ ____________.

A

alternative splicing

49
Q

Once the mRNA transcript exits into the cytoplasm, it begins ____________.

A

translation

50
Q

The ____________ is composed of proteins and rRNA. It brings the mRNA message together with the charged aminoacyl-tRNA complex to generate the protein.

A

ribosome

51
Q

What are the 3 stages of translation?

A
  1. initiation
  2. elongation
  3. termination
52
Q

In prokaryotes, the small ribosomal unit binds to the ________-____________ sequence in the 5’ ________________ region of the mRNA.

A

Shine-Dalgarno; untranslated

53
Q

In eukaryotes, the small subunit binds to the ____ ____ structure.

A

5’ cap

54
Q

The charged ________ ________ binds to the AUG ________ ________ through base-pairing with its anti-codon within the P site of the ribosome.

A

initiator tRNA, start codon

55
Q

After the small subunit binds, the ________ subunit then binds, forming the completed initiation complex. This is assisted by ____________ ________ that are not permanently associated with the ribosome.

A

large; initiation factors

56
Q

What are the 3 main binding sites of ribosomes?

A
  1. A site
  2. P site
  3. E site
57
Q

The A site holds the incoming ____________-________ complex.

A

aminoacyl-tRNA

58
Q

What determines the A site?

A

the mRNA codon

59
Q

The P site holds the ________ that carries the growing polypeptide chain. A ____________ bond is formed as the polypeptide is passed from the tRNA in the P site to the tRNA in the A site.

A

tRNA; peptide

60
Q

This requires ____________ ____________, an enzyme that is part of the large subunit.

A

peptidyl transferase

61
Q

____ is used for energy during the formation of peptide bonds.

A

GTP

62
Q

The E site is where the now inactivated ________ pauses transiently before exiting the ribosome.

A

tRNA

63
Q

As the now-uncharged tRNA enters the E site, it quickly ________ from the mRNA and is ready to be recharged.

A

unbinds

64
Q

____________ ________ assist by locating and recruiting aminoacyl-tRNA along with ____, while helping to remove ____ once the energy has been used.

A

elongation factors; GTP, GDP

65
Q

When any of the three stop codons moves into the A site, a protein called ________ ________ binds to the termination codon, causing a water molecule to be added to the polypeptide chain.

A

release factor

66
Q

The addition of a water molecule to the polypeptide chain allows ________ ____________ and ____________ ____________ to hydrolyze the completed polypeptide chain from the final tRNA.

A

peptidyl transferase; termination factors

67
Q

A specialized class of proteins called ____________ assist in the protein-folding process.

A

chaperones

68
Q

____________ is the addition of a phosphate group by protein ________ to activate or deactivate proteins.

A

phosphorylation; kinase

69
Q

Phosphorylation in eukaryotes is most commonly seen with which 3 amino acids?

A
  1. serine
  2. threonine
  3. tyrosine
70
Q

____________ is the addition of carboxylic acid groups, usually to serve as ________-binding sites.

A

carboxylation; calcium

71
Q

________________ is the addition of oligosaccharides as proteins pass through the ____ and ________ ________ to determine cellular destination.

A

glycosylation; ER, Golgi apparatus

72
Q

____________ is the addition of lipid groups to certain membrane-bound enzymes.

A

prenylation

73
Q

This type of structure is called an ____________ - a cluster of genes transcribed as a single mRNA.

A

operon

74
Q

The ____________ gene codes for the protein of interest.

A

structural

75
Q

Upstream of the structural gene is the ____________ site, a nontranscribable region of DNA that is capable of binding a ________ protein.

A

operator; repressor

76
Q

Further upstream is the ____________ site, which is similar in function to promoters in eukaryotes; it provides a place for ________ ____________ to bind.

A

promoter; RNA polymerase

77
Q

Further upstream is the ____________ gene, which codes for a protein known as the ____________.

A

regulator; repressor

78
Q

In ____________ systems, the repressor is bonded tightly to the operator system and thereby acts as a roadblock. RNA polymerase is unable to get from the promoter to the structural gene because the ________ is in the way.

A

inducible; repressor

79
Q

____________ systems allow constant production of a protein product.

A

repressible

80
Q

In contrast to the inducible system, the repressor made by the ____________ gene is inactive until it binds to a ____________.

A

regulator; corepressor

81
Q

____________ ________ are transcription-activating proteins that search the DNA looking for specific DNA-binding motifs.

A

Transcription factors

82
Q

The ____-________ domain binds to a specific nucleotide sequence in the promoter region or to a DNA ____________ ____________.

A

DNA-binding; response element

83
Q

The ____________ ________ allows for the binding of several transcription factors and other important regulatory proteins.

A

activation domain

84
Q

Several response elemnts may be grouped together to form an ____________, which allows for the control of one gene’s expression by multiple signals.

A

enhancer

85
Q

________________ is tightly coiled DNA that appears dark under the microscope. It is ____________.

A

heterochromatin; inactive

86
Q

____________, on the other hand, is looser and appears light. These genes are ________.

A

euchromatin; active

87
Q

________ ____________ are involved in chromatin remodeling and acetylate lysine residues found in the ________ terminal tail regions of histone proteins.

A

histone acetylases

88
Q

____________ of histone proteins decreases the positive charge on lysine residues and weakens the interaction of the ________ with DNA, resulting in an open ____________ conformation that allows easy access.

A

acetylation; histone; chromatin

89
Q

____________ ____________ are proteins that function to remove acetyl groups from histones, which results in a closed chromatin conformation.

A

histone deacetylases

90
Q

____ ____________ is also involved in chromatin remodeling and regulation of gene expression levels. Methylation is often linked with ____________ of gene expression.

A

DNA metyhlation; silencing

MCAT Biochemistry (13 decks)

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