12: Gene Expression Flashcards
Module 3, Lesson 1 (127 cards)
1
Q
An organism’s genome encodes…
A
Functional molecules
2
Q
____ and ____ are functional molecules.
A
RNA and proteins
3
Q
True or false:
The proportion of the genome that codes for functional molecules is constant across all species.
A
False
4
Q
Approximately ____ of the human genome codes for functional molecules.
A
1-2%
5
Q
A discrete nucleotide that codes for RNA or protein is called a…
A
Gene
6
Q
____ is the process by which DNA is converted into RNA.
A
Transcription
7
Q
____ is the process by which RNA is converted into polypeptides.
A
Translation
8
Q
The central dogma of biology states that…
A
The output of gene expression is proteins.
9
Q
The central dogma of biology describes the process by which…
A
DNA is converted into RNA, which is then converted into proteins.
10
Q
The enzyme that synthesizes an RNA copy of DNA template strands is…
A
RNA polymerase
11
Q
Like DNA polymerase, RNA polymerase catalyzes…
A
Phosphodiester bond formation
12
Q
RNA polymerase synthesizes RNA from the ____ end to the ____ end.
A
5’ to 3’
(the same as DNA polymerase)
13
Q
RNA polymerase uses ____ strand(s) of DNA as a template.
A
1
14
Q
True or false:
RNA polymerase requires a primer to begin synthesis.
A
False
Unlike DNA polymerase, RNA polymerase can begin synthesis without a primer.
15
Q
To transcribe RNA, RNA polymerase must be located at the…
A
Promoter
16
Q
What is the promoter?
A
A sequence of nucleotide that serves as the binding site upstream (in front of) the gene to be transcribed.
17
Q
Transcription begins at the ____, which is the nucleotide designated…
A
Start site ; +1
18
Q
List the five main types of RNA.
A
- Messenger RNA (mRNA)
- Ribosomal RNA (rRNA)
- Transfer RNA (tRNA)
- Small-nuclear RNA (snRNA)
- Micro RNA (miRNA)
19
Q
What are the functions of messenger RNA?
(two)
A
- Acts as an intermediate in the flow of genetic information
- Codes for proteins
20
Q
What are the functions of ribosomal RNA?
(two)
A
- Interacts with proteins to form the ribosome
- Some catalyze protein synthesis
21
Q
What is the function of transfer RNA?
A
Uses information from mRNA to deliver the correct amino acid during translation
22
Q
What is the function of small-nuclear RNA?
A
Involved in pre-mRNA splicing (removing non-coding sequences from the mRNA)
23
Q
What is the function of micro RNA?
A
Regulates the expression of some genes
24
Q
Which types of RNA are not involved in translation?
A
snRNA
miRNA
25
List the main steps of the initiation phase of transcription.
1. RNA polymerase binds to the promoter, along with the sigma subunit
2. RNA polymerase reaches the transcription start site
3. RNA polymerase unwinds the DNA helix
4. The first complementary RNA nucleotide is incorporated
26
The strand of DNA from which RNA is synthesized is termed the...
Template strand
27
The strand of DNA which the completed RNA strand is nearly identical to is the...
Coding strand
28
The new RNA molecule is synthesized antiparallel to the...
Template strand
29
During transcription, the complementary base for adenine becomes...
Uracil
30
The elongation phase of transcription begins after about ____ nucleotide(s) are synthesized.
10
31
List the 3 major components of the transcription bubble.
1. RNA polymerase
2. Part of the exposed template DNA strand
3. Part of the new RNA base-paired to the template DNA
32
Transcription continues until...
A terminator sequence is encountered and transcribed.
33
The terminator sequence codes for RNA that...
Pairs to itself, creating a hairpin structure
34
The hairpin structure formed by the terminator sequence disrupts...
The interactions between DNA, RNA, and RNA polymerase
35
In eukaryotes, transcription occurs in the...
Nucleus
36
# True or false:
Both eukaryotes and prokaryotes have only one kind of RNA polymerase.
False
Eukaryotes have three different RNA polymerases.
37
In eukaryotes, mRNA is synthesized by...
RNA polymerase II
## Footnote
(also the best understood of the three RNA polymerases)
38
List the major differences between eukaryotic and prokaryotic transcription.
| (four)
1. Eukaryotes have 3 RNA polymerases
2. The promoter's position and sequence is different
3. Eukaryotic transcription is initiated by transcription factors
4. The initial mRNA molecule is modified in eukaryotes
39
Compared to prokaryotes, the mechanism for binding RNA to the promoter is ____ complicated in eukaryotes.
More
40
In eukaryotes, RNA polymerase II is recruited to the promoter and activated by a series of proteins called...
Transcription factors
41
# True or false:
In eukaryotes, the intial mRNA molecule must undergo additional processing to become a mature molecule.
True
42
The initial molecule of mRNA synthesized is called the...
Primary transcript
43
List the three ways in which eukaryotes modify mRNA.
1. A cap is added to the 5' end
2. A 3' poly-A tail is added to the 3' end
3. Non-coding regions are removed
44
What is the purpose of the 5' cap?
Protects the mRNA from degradation and helps to align it during translation
45
What is the purpose of the 3' poly-A tail?
Protects the mRNA from degradation
46
Regions of mRNA that specify amino acids are called...
Exons
47
Regions of mRNA that do not specify amino acids and are not translated are called...
Introns
48
Introns are removed from the mRNA by the...
Spliceosome
49
During splicing, introns are ____ and exons are ____.
Removed ; spliced together
50
# True or false:
Different genes have different numbers of introns and exons.
True
51
# True or false:
Only eukaryotes have introns.
True
52
The output of splicing is...
Mature mRNA
53
# True or false:
A single primary transcript can code for multiple proteins, depending on how it is spliced.
True
54
How can a single primary transcript code for multiple different proteins?
Different exons are included when it is spliced.
55
The second step in gene expression is...
Translation
56
Translation is the process of...
Protein synthesis
57
During translation...
The nucleotide sequence of mRNA is converted to a polypeptide sequence and eventually a functional protein
58
List the three main components involved in translation.
1. mRNA
2. tRNA
3. rRNA
59
Protein synthesis proceeds from the ____-terminus to the ____-terminus
N to C
60
The mRNA sequence is always read in a ____ to ____ direction.
5' to 3'
61
In prokaryotes, mRNA contains ____ coding sequence(s).
Multiple
62
Prokaryotic genes are organized into...
Operons
63
# True or false:
Some regions of prokaryotic mRNA do not code for proteins.
True
64
____ are located at the beginning and end of prokaryotic RNA.
Untranslated regions
(UTRs)
65
Untranslated regions are regions that do not...
Code for any proteins
66
Eukaryotic mRNA contains ____ coding sequence(s).
One
67
# True or false:
Eukaryotic genes may be organized into operons.
False
Operons are only found in prokaryotes.
68
In prokaryotic mRNA, each coding region begins with a...
Translation start site
69
An amino acid is specified by a sequence of three nucleotides called a...
Codon
70
Each codon specifies ____ amino acid(s).
One
71
The codon AUG, which does for methionine, is termed the...
"Start codon"
72
The first codon in a coding sequence is almost always...
AUG
73
There are a total of ____ possible codons.
64
74
# True or false:
More than one codon can specify the same amino acid.
True
75
____ codons specify an amino acid.
61
76
____ codons code for "stop codons".
3
77
The genetic code is...
Redundant (degenerate)
78
# True or false:
The genetic code is practically universal.
True
79
There are ____ possible reading frames for any mRNA.
3
80
The reading frame used for an mRNA depends on...
The nucleotide at which reading starts.
81
During translation, what is the function of tRNA?
Carries amino acids to the ribosomes, where they are assembled into polypeptides.
82
tRNA self-folds into a ____ shape.
Cloverleaf
83
What creates the 3D stucture of tRNA?
Internal complementary base pairing
84
List the two important regions found on opposite ends of the tRNA molecule.
1. 3' acceptor end
2. Anticodon loop
85
What is the function of the 3' acceptor end?
Amino acids are loaded onto it
86
What is the anticodon loop and what is its function?
A 3-nucleotide sequence that recognizes and binds to a complementary codon in the mRNA.
87
tRNA and the amino acids it transports are able to interact with the correct codon due to the...
Anticodon loop
88
Interactions between tRNA and mRNA are based on...
Base pairing using hydrogen bonds
89
# True or false:
tRNA--mRNA base pairing is fundamentally the same as nucleotide base pairing in DNA strands.
False
90
# True or false:
Some tRNA molecules can recognize more than one codon.
True
91
The less stringent interactions between the 3' end of the codon and the 5' end of the anticodon are called...
"Wobble" or "wobble pairing"
92
"Wobble pairing" is also called...
Relaxed base pairing
93
# True or false:
It is possible for the codon UUU to pair with the anticodon AAG.
True
Due to relaxed base pairing, G is able to pair with U.
94
List the two main subunits of the ribosome.
1. Large subunit
2. Small subunit
## Footnote
wow biologists are so creative
95
What is the function of the large subunit?
Catalyzes peptide bond formation
96
What is the function of the small subunit?
Decodes the mRNA sequence
97
List the three tRNA binding sites found in the ribosome.
1. Exit site (E-site)
2. Peptidyl site (P-site)
3. Aminoacyl site (A-site)
98
What tRNA molecule does the E-site bind to?
The tRNA molecule from the previous amino acid
| (the amino acid that was just added to the c-terminus)
99
Which tRNA molecule does the P-site bind to?
The tRNA currently attached to the growing peptide chain.
100
Which tRNA molecule does the A-site bind to?
The tRNA for the next amino acid to be added to the chain.
101
List the steps of the initiation phase of translation.
1. The small subunit binds to the mRNA to determine the translation start site
2. Initiator tRNA binds to the start codon at the P-site
3. The large subunit binds
4. The A-site and E-site are empty
102
In prokaryotes, the small subunit binds to the...
Ribosome binding site
(RBS)
103
In eukaryotes, the small subunit binds to the...
5' cap
104
# True or false:
The methionine involved in prokaryotic initiation is modified.
True
| (the eukaryotic version is unmodified)
105
During the elongation phase of translation...
Successive amino acids are added
106
List the major steps of the elongation phase of translation.
1. The ribosome catalyzes peptide bond formation
2. The A-site receives an amino acid
3. A peptide bond forms between the A-site amino acid and the P-site amino acid
4. The P-site amino acid shifts to the E-site, and the A-site amino acid shifts to the P-site
107
The elongation phase of translation begins when...
The A-site is occupied for the first time
108
Translation continues until...
A stop codon is encountered and enters the A-site
109
Instead of being recognized by a tRNA molecule, the stop codon is recognized by the...
Release factor
110
What happens after the completed polypeptide is released?
The ribosome shifts one "codon", then disassembles.
111
Proteins are important to a cell's...
Structure and function
112
Mutations alter ____ and ____ sequences.
Gene and protein
113
A ____ does not alter the resulting amino acid, because the modified codon still specifies the same amino acid.
Silent mutation
114
A ____ is a change to the nucleotide that also changes the encoded amino acid.
Missense mutation
115
A ____ is a change in a nucleotide that results in a stop codon.
Nonsense mutation
116
What happens as a result of a nonsense mutation?
Translation is terminated prematurely, resulting in a nonfunctional protein.
117
A ____ is a mutation that occurs when one nucleotide base is swapped with another.
Base substitution
118
List the three types of base subsititution mutations.
1. Silent
2. Missense
3. Nonsense
119
A ____ occurs when a base is either added to or deleted from a DNA sequence.
Frameshift mutation
120
What happens as a result of a frameshift mutation?
The downstream reading frame is altered, which almost always affects protein function.
121
List the four main types of chromsome mutations.
1. Deletion
2. Duplication
3. Inversion
4. Translocation
122
Deletion occurs when part of a chromsome is...
Lost / deleted
(1 or more genes are lost)
123
Duplication occurs when part of a chromosome is...
Copied
(1 or more genes are copied)
124
Inversion occurs when part of a chromosome is...
In reverse order
(affects gene function or may combine genes)
125
Translocation occurs when part of a chromosome is...
Moved onto another chromosome
(can combine genes)
126
Mutations are the starting point for...
Evolution
127
A balance must exist between the ____ and the ____.
Variance of new mutations and the health of the species
