gene expression 2 Flashcards
(102 cards)
1
Q
Polypeptides are made from mRNA during
A
translation
2
Q
The genetic code specifies the relationship between the sequence of nucleotides in ______ and the sequence of amino acids in a polypeptide.
A
mRNA
3
Q
There are __ nucleotide bases in one codon.
A
3
4
Q
How many amino acids can be specified by a codon?
A
1
5
Q
Which of the following statements best describes the genetic code?
- It is universal; no exceptions have been discovered
- It is not universal; a lot of exceptions have been discovered
- It is nearly universal; only a few rare exceptions have been discovered
A
It is nearly universal; only a few rare exceptions have been discovered
6
Q
The synthesis of __ using information within the mRNA is called translation.
A
polypeptides, proteins, polypeptide, or protein
7
Q
Because the same amino acid can be specified by more than one codon, the genetic code is characterized as ______.
A
degenerate
8
Q
What is the purpose of the genetic code?
A
It specifies the relationship between mRNA and polypeptide sequences.
9
Q
Codons that specify the same amino acid typically differ in the base at position number __.
A
3
10
Q
The genetic code is read in groups of three nucleotide bases known as __.
A
codons
11
Q
The start codon encodes the amino acid
A
methionine or met
12
Q
A codon in a messenger RNA molecule consists of ______ nucleotides. Each mRNA codon specifies ______ amino acid(s).
A
three; one
13
Q
The portion of an mRNA sequence that specifies the amino acid sequence of a polypeptide is called the __ sequence.
A
coding
14
Q
The genetic code is said to be nearly __ because with few exceptions, all organisms use the same code.
A
universal or identical
15
Q
The end of translation is signaled by the
A
stop codon
16
Q
The genetic code is said to be __ because more than one codon can specify the same amino acid.
A
degenerate or redundant
17
Q
In most cases, codons that specify the same amino acid vary in the ________ base.
A
third
18
Q
What part of a tRNA binds to the codon of a messenger RNA molecule?
A
Anticodon
19
Q
What amino acid is specified by the start codon?
A
Methionine
20
Q
There are __ nucleotides are in an anticodon.
A
3
21
Q
A coding sequence specifies the amino acid sequence of a(n)
A
polypeptide or protein
22
Q
Which part of a tRNA molecule binds to a codon on mRNA to determine which amino acid will be added to a growing polypeptide?
A
Anticodon
23
Q
A stop codon specifies the end of
A
translation.
24
Q
Which RNA molecule functions as an intermediary between an mRNA codon and an amino acid?
A
The tRNA
25
Because the same amino acid can be specified by more than one codon, the genetic code is characterized as ______.
degenerate
26
The components mRNA, tRNA, ribosomes, and translation factors must be made by a cell so that __ can be synthesized.
polypeptides, proteins, or protein
27
What is the function of the anticodon of a tRNA molecule?
It binds to a codon on an mRNA molecule.
28
The three major types of RNA are involved in translation. The information to synthesize a polypeptide sequence is contained in __; Amino acids are brought to the ribosome by __; and __ is a major component of the ribosome.
Blank 1: mRNA or messengerRNA
Blank 2: tRNA or transferRNA
Blank 3: rRNA or ribosomalRNA
29
In a tRNA molecule, the anticodon is a ______-base sequence.
three
30
The structural features common to all transfer RNAs include a stem-loop containing a(n) __ that is complementary to the codon on mRNA and an acceptor stem where a(n) __ __ can be attached.
Blank 1: anticodon or anti-codon
Blank 2: amino
Blank 3: acid
31
The __ in tRNA binds to a codon in an mRNA.
anticodon
32
A __-__ structure in a tRNA molecule consists of a region where the RNA is double-stranded due to complementary base pairing, and another region without base pairing.
stem-loop or hair-pin
33
The __ molecule is attached to an amino acid and has an anticodon that can base pair with a codon.
tRNA or transferRNA
34
Which of the following components are necessary for translation?
- translation factors
- RNA polymerase
- ribosomes
- tRNA
- spliceosomes
- mRNA
translation factors
ribosomes
tRNA
mRNA
35
mRNA function
contains information needed to synthesize a polypeptide
36
tRNA function
binds to a codon and carries the appropriate amino acid to be added to the polypeptide
37
ribosome function
catalyzes the formation of peptide bonds to synthesize a polypeptide
38
translation factor function
proteins required for translation
39
What structural features are common to all tRNAs?
- Acceptor stem for amino acid attachment
- A, P, and E sites
- Cloverleaf pattern with three stem-loops
- Loop that attaches to the spliceosome
Acceptor stem for amino acid attachment
Cloverleaf pattern with three stem-loops
40
What must be attached to the 3' end of a tRNA molecule in order for translation to proceed properly?
An amino acid
41
A tRNA molecule assumes a stem-loop structure which results from ________ bonds that form between nearby regions.
hydrogen
42
What is attached to a charged tRNA molecule?
An amino acid
43
The components mRNA, tRNA, ribosomes, and translation factors must be made by a cell so that __ can be synthesized.
polypeptides, proteins, or protein
44
The three major types of RNA are involved in translation. The information to synthesize a polypeptide sequence is contained in __; Amino acids are brought to the ribosome by __; and __ is a major component of the ribosome.
Blank 1: mRNA or messengerRNA
Blank 2: tRNA or transferRNA
Blank 3: rRNA or ribosomalRNA
45
What is the site of translation?
Ribosome
46
In order for translation to be accurate, the appropriate amino acid must be attached to the:
3' end of the correct tRNA
47
What are the two subunits of a ribosome called?
Large and small subunits
48
A __-__ structure in a tRNA molecule consists of a region where the RNA is double-stranded due to complementary base pairing, and another region without base pairing.
stem loop or hairpin
49
The ribosomal subunits contain two types of macromolecules:
Blank 1: protein, proteins, or polypeptides
Blank 2: rRNA, RNA, RNA molecules, ribonucleic acid, ribosomalRNA, RNAs, nucleic acids, nucleic acid, ribonucleicacid, or RNAmolecules
50
A tRNA molecule with its attached amino acid is called a(n) __ tRNA.
charged, aminoacyl, or aminoacylated
51
Which of the following components are necessary for translation?
- translation factors
- RNA polymerase
- tRNA
- spliceosomes
- mRNA
- ribosomes
translation factors
tRNA
mRNA
ribosomes
52
What are the names of the three sites where tRNA molecules bind to the ribosome?
- the exit site
- the peptidyl site
- the anticodon site
- the aminoacyl site
- the codon site
the exit site
the peptidyl site
the aminoacyl site
53
Translation occurs on structures called
ribosomes
54
Translation occurs in three stages: initiation, __, and __.
elongation
| termination
55
A(n) __ is composed of structures called the large and small subunits.
ribosome
56
Which macromolecules are found in ribosomes?
- polysaccharides
- DNA
- RNA
- protein
- phospholipids
RNA
protein
57
During the initiation stage of translation, an mRNA molecule, the first (initiator) __ molecule, and the ribosomal subunits associate. During elongation, __ bonds are formed between amino acids. Finally, translation ends when the ribosome reaches a(n) __ codon.
Blank 1: tRNA or transferRNA
Blank 2: peptide or covalent
Blank 3: stop, termination, nonsense, or non-sense
58
A ribosome contains three discrete sites where tRNAs may be located. These are known as the A or __ site, the P or __ site, and the E or __ site.
Blank 1: aminoacyl
Blank 2: peptidyl
Blank 3: exit
59
What molecules must assemble during the initiation stage of translation?
- ribosomal subunits
- the first tRNA
- mRNA molecule
- the DNA molecule
ribosomal subunits
the first tRNA
mRNA molecule
60
The stages of translation are called:
initiation, elongation and termination
61
In most cases, the start codon used for translation is
AUG or ATG
62
What are the two subunits of a ribosome called?
Large and small subunits
63
During initiation of translation, the initiator tRNA recognizes the __ codon in mRNA and binds to it.
start, AUG, starting, initiation, methionine, or starter
64
The ribosomal subunits contain two types of macromolecules:
Blank 1: protein, proteins, or polypeptides
Blank 2: rRNA, RNA, RNA molecules, ribonucleic acid, ribosomalRNA, RNAs, nucleic acids, nucleic acid, ribonucleicacid, or RNAmolecules
65
key events that occur during Initiation
The mRNA, tRNA, and ribosomal subunits are assembled.
66
key events that occur during Elongation
Peptide bonds are formed between amino acids to synthesize a polypeptide.
67
key events that occur during termination
A release factor binds to the A site of the ribosome.
68
During the initiation phase of translation, a complex is formed between an mRNA molecule, the first __, and the __ subunits.
Blank 1: tRNA, transferRNA, transfer RNA, or tRNA molecule
| Blank 2: ribosomal or ribosome
69
In a strand of mRNA, the nucleotide sequence of the start codon is
AUG.
70
Which tRNA recognizes and binds to the start codon in mRNA?
Initiator tRNA
71
In bacteria, translation is initiated when a(n) __ molecule binds to the small ribosomal subunit.
mRNA, messengerRNA, or RNA
72
Which macromolecules are found in ribosomes?
- phospholipids
- DNA
- polysaccharides
- protein
- RNA
protein
RNA
73
The __ stage of translation involves the covalent bonding of amino acids to each other, one at a time.
elongation or second
74
During the initiation stage of translation, an mRNA molecule, the first (initiator) __ molecule, and the ribosomal subunits associate. During elongation, __ bonds are formed between amino acids. Finally, translation ends when the ribosome reaches a(n) __ codon.
Blank 1: tRNA or transferRNA
Blank 2: peptide or covalent
Blank 3: stop, termination, nonsense, or non-sense
75
What is attached to a peptidyl tRNA?
A short polypeptide
76
What molecules must assemble during the initiation stage of translation?
the first tRNA
mRNA molecule
ribosomal subunits
77
Because the anticodon in the tRNA is complementary to the codon in the mRNA, during the elongation phase of translation, a charged tRNA carrying a single amino acid binds to the ______ site.
A
78
In most cases, the start codon used for translation is
AUG or ATG
79
To obtain the energy required for tRNA to bind to the A site, elongation factors hydrolyze:
GTP
80
Identify the stage of translation in which polypeptide synthesis occurs.
Elongation
81
The peptidyl transfer reaction involves the removal of the polypeptide from the tRNA in the ______ site and its transfer to the amino acid in the ______ site.
P ; A
82
A tRNA with a polypeptide attached to it is called a(n):
peptidyl tRNA
83
A charged tRNA molecule carrying a single amino acid binds to the A site because the anticodon in the tRNA has a sequence that is __ to the codon in the mRNA.
complementary or corresponding
84
Proteins functioning as elongation factors provide the energy for binding tRNA to the ______ site.
A
85
In bacteria, translation is initiated when a(n) __ molecule binds to the small ribosomal subunit.
mRNA, messengerRNA, or RNA
86
During the elongation stage of translation, the polypeptide is removed from the tRNA in the P site and added to the tRNA in the A site. This event is termed the ___ ____ reaction.
Blank 1: peptidyl
| Blank 2: transfer or transferase
87
The peptidyl transferase center, which catalyzes the peptidyl transfer reaction, is composed of several proteins and
rRNA
88
What is attached to a peptidyl tRNA?
A short polypeptide
89
During the translocation step of protein synthesis, the ribosome moves toward the
3' end of mRNA by exactly one codon
90
Because the anticodon in the tRNA is complementary to the codon in the mRNA, during the elongation phase of translation, a charged tRNA carrying a single amino acid binds to the ______ site.
A
91
To obtain the energy required for tRNA to bind to the A site, elongation factors hydrolyze:
GTP
92
In the process of protein synthesis, what recognizes the three stop codons?
A protein called release factor
93
The three-dimensional structure of a release factor protein mimics the structure of
tRNAs
94
The peptidyl transfer reaction that occurs in translation is catalyzed by
a region in the 50S subunit
95
What happens as a result of the translocation step of protein synthesis?
- The next codon moves into the P site
- The tRNA in the P site moves into E site
- The tRNA in the A site moves into P site
- The next codon moves into the A site
- The tRNA in the P site moves into A site
- The tRNA in the A site moves into E site
The tRNA in the P site moves into E site
The tRNA in the A site moves into P site
The next codon moves into the A site
96
A charged tRNA molecule carrying a single amino acid binds to the A site because the anticodon in the tRNA has a sequence that is __ to the codon in the mRNA.
complementary or corresponding
97
During translation, the stop codons are recognized by a protein called a(n) )__ factor.
release
98
The translation release factor has a 3-D structure that resembles that of:
tRNA
99
During bacterial translation, when a stop codon is encountered, a protein known as a(n) _ factor binds to the A site, which triggers the removal of the _ from the tRNA in the P site.
Blank 1: release
| Blank 2: polypeptide or protein
100
During the translocation step of protein synthesis, the ribosome moves toward the
3' end of mRNA by exactly one codon
101
Because the anticodon in the tRNA is complementary to the codon in the mRNA, during the elongation phase of translation, a charged tRNA carrying a single amino acid binds to the ______ site.
A
102
The three-dimensional structure of a release factor protein mimics the structure of
tRNA
