chapter 7 Flashcards
(151 cards)
1
Q
The segments of DNA that are transcribed into RNA are called
A
genes
2
Q
RNA is made of nucleotides that are linked by
A
phosphodiester
bonds
3
Q
Same phosphodiester bond that links nucleotides in RNA…
A
is same as DNA
4
Q
the structure of
RNA differs from that of DNA
in __ ways
A
3
5
Q
RNA and DNA differences
A
1.RNA contains ribose not deoxyribose, has an additional -OH group.
2. RNA contains uracil instead of thymine in DNA
3. RNA is single stranded, no double helix
6
Q
The nucleotides in RNA are
A
ribonucleotides
7
Q
Uracil differs from thymine by the
A
absence of methyl group
8
Q
Uracil, like thymine, can form
A
base-pairs with adenine (A)
9
Q
How does RNA fold into a variety of shapes…
A
forming base-pairs between
nucleotides within the same strand
10
Q
Base pairing always occurs between
A
anti-parallel strands
11
Q
The ability to fold into shapes allows RNA to perform…
A
structural, regulatory, or catalytic roles in cells
12
Q
__ produces an RNA molecule that is
complementary to one strand of DNA
A
Transcription
13
Q
One of the two strands of DNA serves as a __ for RNA synthesis
A
template
14
Q
Ribonucleotides are added
A
1 by 1 to rna molecule
15
Q
The nucleotide sequence of the RNA chain is determined by
A
complementary base pairing with the DNA template strand
16
Q
RNA is transcribed in what direction….
Nucleotides are added to what end…
A
5’-to-3’ direction (nucleotides are added to the 3’ end)
17
Q
The DNA template strand is read in the
A
3’-to’5’ direction
18
Q
same base sequence as RNA transcript
A
Non-template strand = coding strand
19
Q
complementary to RNA transcript
A
Template strand
20
Q
Write the sequence of the RNA transcript that is generated using the bottom strand of the following DNA sequence as the template:
5’-TTTTT-3’
3’-AAAAA-5’
A
3’-AAAAA-5” (template)
5’- UUUUU-3’ (rna transcript sequence)
21
Q
Write the sequence of the RNA transcript that is generated using the top strand of the following DNA sequence as the template:
5’-CGGAATC-3’
3’-GCCTTAG-5’
A
5’-CGGAATC-3’ (template)
3’- GCCUUAG-5’ rna transcript sequence)
read 5’-GAUUCCG-3’
22
Q
Using the DNA sequence below, identify the coding strand for the following RNA
transcript: 5’-AUCGA-3’
DNA sequence:5’-ATCGA-3’
3’-TAGCT-5’
A
5’-ATCGA-3’
23
Q
is an enzyme that catalyzes the formation of phosphodiester
bonds that link ribonucleotides together
A
RNA polymerase
24
Q
RNA polymerase unwinds the DNA helix to expose a region of the..
A
template strand for complementary base pairing
25
The RNA strand elongates one nucleotide at a time in the
5’-to-3’ direction
26
used to direct the synthesis of proteins In eukaryotes
mRNA
27
each mRNA carries information transcribed from a
single gene
28
What kind of rna play regulatory,
structural and catalytic roles in cells
Noncoding RNAs (e.g. rRNA, tRNA, miRNA)
29
The promoter is located
upstream (a.k.a. before) of the starting point for RNA synthesis
30
binds the promoter and begins transcription
RNA polymerase
31
Transcription proceeds until RNA polymerase encounters a
terminator
32
Every promoter has a
polarity
33
Bacterial promoters contain __ different nucleotide sequences that are laid out in a specific __ order
2, 5’-to’3’
34
RNA polymerase always moves in the __ direction on the template DNA strand
3’-to-5’
35
what determines which strand will serve as the
template?
The polarity (orientation) of the promoter sequence at the
beginning of each gene
36
Terminators have specific...
nucleotide sequences
37
Terminator sequences are
palindromic
38
cause a stem-loop structure to form in the RNA
transcript
terminator sequences
39
What causes the transcipt to dissociate from the DNA template
stem loop stricture in the RNA transcript
40
Transcription in bacteria: Bacterial RNA polymerase contains a subunit called a
sigma factor
41
recognizes and binds the promoter of a gene
sigma factor
42
in bacterial transcription, once transcription begins what is released
sigma factor
43
In bacterial transcription, RNA polymerase opens the double
helix immediately in
front of the promotoer
44
synthesizes a chain of RNA by base pairing with the template strand
RNA polymerase
45
When RNA polymerase reaches the terminator...
It stops and releases the DNA template and the
RNA transcript
46
Bacteria use a __ RNA polymerase for transcription, while eukaryotic cells use __
single, 3 (RNA poly 1, 11, 111)
47
Which polymerase transcribe genes encoding tRNA, rRNA and other small RNAs (regulatory RNA)
RNA polymerase I and III
48
which polymerase transcribes mRNA and other RNAs
RNA polymerase II
49
Bacterial RNA polymerase (with its sigma factor) initiates transcription on its own, while eukaryotic RNA polymerases require a...
large set of
accessory proteins
50
Accessory proteins can include
general transcription factors
51
assemble at
each promoter along with the polymerase before transcription can
begin
general transcription factors
52
Transcription in eukaryotes requires the
General Transcription Factors
53
Step 1 in transcription factors of eukaryotes
TFIID binds a short sequence
of DNA that is rich in T and A nucleotides à called the “TATA box
54
TFIID binding to the TATA box...
distorts DNA double helix
55
Step 2 in transcription factors of eukaryotes
TFIID recruits RNA
polymerase II and others to form a transcription initiation complex
56
Step 3 in transcription factors of eukaryotes
TFIIH pulls apart the double
helix at the transcription start point and phosphorylates RNA
polymerase II
57
Step 4 in transcription factors of eukaryotes
Transcription begins
58
Eukaryotic transcription occurs in the
nucleus
59
Translation occurs on ribosomes in the
cytosol
60
Before a eukaryotic mRNA can be translated into protein, it must be transported
out of the nucleus
61
Before RNA is exported, it must go through
RNA processing
62
What is involved in RNA processing
capping, splicing and polyadenylation
63
Processing occurs ___ transcription
during and after
64
RNA-processing proteins bind
to the phosphorylated tail of __, it gives them access to the
RNA polymerase II, RNA transcript as it emerges from the polymerase
65
modifies the 5’ end of the transcript by adding an
atypical guanine nucleotide with a methyl group
RNA capping
66
addition of a series of repeated adenine (A) nucleotides to the 3’ end
Polyadenylation
67
Capping and polyadenylation promote the
stability, export and
translation of mRNAs
68
RNA capping and polyadenylation occur on all
RNA transcripts that become
mRNA molecules
69
contain single stretches of nucleotides that encode
the amino acid sequence of proteins
Bacterial genes
70
The coding sequences of most eukaryotic genes are interrupted by noncoding “intervening sequences” called
introns
71
The protein-coding sequences are called “expressed sequences” or
exons
72
Most of the nucleotide sequences
of introns are
unimportant
73
involves the precise removal of introns
splicing
74
The intron is removed as a __
structure, which is degraded in the __
lariat, nucleus
75
Once an intro is removed, the two exons are joined together...
covalently
76
allows increased genetic diversity and complexity
Alternative splicing
77
Fully processed mRNAs are recognized as
mature transcripts
that are allowed to leave the nucleus
78
Proteins bind to __ cap, splice junctions and poly-A tail and promote:
5', transport out of the nucleus, mRNA stability, translation
79
Prokaryotes don't have a nucleus, so transcription and translation happen in the
cytosol
80
Prokaryotes don't need
RNA processing
81
In eukaryotes, transcription happens in the
nucleus
82
In eukaryotes, mRNA must be processed via
5’ capping, 3’ polyadenylation, and splicing before it is exported into the
cytosol and translated
83
mitochondria and chloroplasts
have their own
RNA polymerases
84
The process of transcription begins with RNA polymerase binding to a region of the gene called a
promotor
85
TFIID contains a subunit called __ that binds to a sequence in the promotor known as __
TATA binding protein, TATA box
86
TFIIH has two important functions:
1. it partially unwinds the DNA to expose the
template strand at the promoter
2. it phosphorylates RNA polymerase II to release it from the general transcription factors
87
cap is added to the 5' end of the mRNA
Capping
88
poly-A-tail pf 100 or more repeated adenine nucleotides is added to the 3' end of the mRNA
Polyadenylation
89
Splicing is performed by a molecular machine known as the
splicesome
90
deflects in splicing are the cause of
some human disease
91
Nucleotides are read in groups of three called
codons
92
__ possible codons used to specify 20 amino acids
64
93
Most amino acids are specified by
2 or more codons
94
__ codons are used as a translation stop signal
3
95
Genetic code can be described as
redundant
96
Each mRNA has 3 possible __, only __ encodes the correct protein sequence
reading frames, 1
97
Small adaptor molecules known as __ are responsible for matching the
proper amino acid to the correct mRNA codon.
tRNAa
98
site of protein synthesis
ribosomes
99
There are __ different nucleotides in mRNA but __ different amino
acids in proteins
4, 20
100
The nucleotide sequence of an mRNA is translated into amino acids
using
codons
101
Each codon consists of nucleotides
3
102
Codons are translated sequentially in the _ direction, without overlaps or spacers
5’ to 3’
103
The genetic code is
redundant
104
In the genetic code, __ codons are used to specific 20 amino acids
64
105
what RNA translate the code
tRNAs
106
Transfer RNAs (tRNAs) fold into a
cloverleaf structure
107
The cloverleaf structure from tRNA folds further into a
L shaped structure
108
set of three nucleotides that bind the complementary
codon in an mRNA molecule
anticodon
109
in the tRNA, the amino acid that matches the codon is __ attached to the single stranded region at the __ end of the tRNA
covalently, 3'
110
Two regions of the tRNA are crucial for translation
amino acid and anticodon
111
In the genetic code, multiple codons...
encode the same amino acid
112
Codons are most variable at the __ position
3rd
113
Some tRNAs require accurate base-pairing only at the
first 2 positions
114
tRNA base pairing can tolerate a mismatch at the __ position
(wobble), 3rd
115
__ tRNAs for __ total codons in humans
48, 61
116
establish the tRNA code
tRNA synthetases
117
covalently attach each amino acid to the appropriate tRNAs
tRNA synthetases
118
There are __ tRNA synthetases
20
119
a key link between the nucleotide and amino acid
languages
tRNA synthetases
120
The same mRNA sequence can specify __ different amino acid sequences, depending on the nucleotide at which translation begins
3
121
Translation begins at the initiation codon __
AUG
122
AUG encodes a
methionine
123
The position of the initiation codon sets the translation __
reading frame
124
catalyzes protein synthesis
ribosome
125
Ribosomes are composed of
one large subunit and one small subunit
126
Eukaryotic ribosomes are made from __ ribosomal RNAs (rRNAs) and more than 80 proteins
4
127
Each ribosome has how many binding sites for mRNA and rRNAs
mRNA- 1
tRNA- 3
128
The ribosome's 3 tRNA binding sites are called
the A site, the P site and the E site
129
Four step cycle of translation...
step 1: growing polypeptide chain is linked to the tRNA in the P site
step 2: new peptide bond is catalyzed by RNA in large ribosomal subunit
step 3: large ribosomal subunit shifts forward to move 2 tRNAs into E and P sites
step 4: small subunit moves forward 2 nucleotides along the mRNA to rejoin large subunit; movement ejects the spent tRNA from E site and resets the ribosome with an empty A site so next tRNA can bind
130
In the first step of translation, to add an amino acid to a growing peptide chain, a
tRNA enters A site, w base pairing on complimentary mRNA
131
In eukaryotes, translation of mRNA begins with __ and requires __
AUG codon, initiator tRNA
132
In eukaryotes. the initiator codon always carries the amino acid
methionine
133
In translation in eukaryotes, Newly made proteins all have methionine as the first amino acid at their
N-terminal end
134
In translation in eukaryotes, __ is loaded into the __ site of the __ ribosomal subunit along with __
initiator tRNA, P, small, translation initiation factors
135
In translation in eukaryotes, the small ribosomal subunit then binds to the __ end of the mRNA
5'
136
After the small ribosomal subunit binds to the mRNA in translation, the small ribosomal subunit then scans the mRNA in the
5’-to-3’ direction until it encounters the first AUG codon
137
In translation in eukaryotes, when the AUG is recognized by the initiator tRNA, several initiation factors dissociate, allowing....
the large ribosomal
subunit to bind
138
in translation in eukaryotes, Because the initiator tRNA is
bound to the P site, protein
synthesis is ready to begin
with the addition of the next
tRNA to the A site
139
to initiate translation in prokaryotes, there's no __ for the small ribosomal subunit to bind on bacterial mRNAs/ Instead ribosomes...
5' cap, bind directly to specific sequences adjacent to coding
regions
140
Most bacteria mRNAs are
polycistronic
141
a single mRNA encodes several different proteins, usually with related functions
polycistronic
142
in translation in prokaryotes each ribosome has...
its own ribosome-binding site instead of scanning for aug
143
How to terminate translation
Stop codons; release factors bind to stop codon in the A-site; peptide chain is transferred to a water molecule, ending synthesis
144
what are the stop codons
UAA, UAG, UGA
145
can be translated by multiple
ribosomes at the same time
A single mRNA
146
simultaneously translate the same mRNA
Polyribosomes
147
A single gene can be transcribed by multiple RNA polymerases at the same time T or F
True
148
Misfolded or damaged proteins and proteins that are meant to be short-lived are degraded by the
proteasome
149
large protein complex that contains enzymes
called proteases
proteasome
150
cut proteins into short peptides
proteases
151
Proteins are marked for degradation by the covalent attachment of
a small protein called
ubiquitin
