Chapter 17 Flashcards
1
Q
Polysomes may be described as
A
Groups of ribosomes
2
Q
The function of tRNA during protein synthesis is to
A
Deliver amino acids to their proper site during protein synthesis
3
Q
How many nucleotides are needed to code for a protein with 450 amino acids?
A
At least 1,350
4
Q
Because codons are nucleotide triplets, the number of nucleotides making up a generic message must be
A
Three times the number of amino acids in the protein product
5
Q
Bacteria can transcribe and translate human genes to produce functional human proteins because
A
The genetic code is nearly universal
6
Q
Stop codons are unique because they
A
Do not code for amino acids that allow a releasing factor to bind to the A site of the ribosome
7
Q
Final stage of translation
A
Termination
8
Q
Elongation (in translation) continues until
A
A stop codon in the mRNA reaches the A site of the ribosome
9
Q
Release factor
A
Bonds directly to the stop codon in the A site
Causes the addition of a water molecule to the polypeptide chain
10
Q
In order for transcription to occur in that strand, there would have to be a specific recognition sequence, called a __, to the left of the DNA sequence indicated
A
Promoter
11
Q
Promoter
A
The DNA sequence where RNA polymerase attaches and initiates transcription
12
Q
RNA polymerase binds
A
In a precise location and orientation on the promoter, determining where transcription starts and which of the two strands of the DNA helix is used as the template
13
Q
Specific sequences of the nucleotides along the DNA mark
A
Where transcription begins
14
Q
The TATA box is a __ that allows for the binding of __ and __
A
Eukaryotic promoter; transcription factors; RNA polymerase II
15
Q
Transcription factors
A
Mediate the binding of RNA polymerase and the initiation of transcription
-after transcription factors are attached to the promoter, RNA polymerase II binds to it
16
Q
Transcription initiation complex
A
The whole complex of transcription factors and RNA polymerase II bound to the promoter
17
Q
RNA molecules that function as enzymes are called
A
Ribozymes
18
Q
The “triplet code” refers to the fact that
A
Three nucleotides code for a single amino acid
19
Q
__ is the synthesis of a polypeptide using information in the mRNA
A
Translation
Cell translates the nucleotide sequence of an mRNA molecule into the amino acid sequence of a polypeptide
20
Q
Sites of translation
A
Ribosomes
21
Q
Generic information of eukaryotic cells is transferred from the nucleus to the cytoplasm in the form of
A
RNA
22
Q
Nuclear envelope separates
A
Transcription from translation in space and time
23
Q
Transcription occurs
A
In the nucleus
And then mRNA is then transported to cytoplasm, where translation occurs
24
Q
An exception to the one gene-one enzyme hypothesis is
A
Not all genes code for enzymes; some genes code for structural proteins such as keratin
25
What is the proper order in the expression of a eukaryotic gene?
Transcription
RNA processing
Translation
Modification of protein
26
DNA ->
RNA -> PROTEIN
27
Genes program
Protein synthesis via genetic messages in the form of mRNA
28
The bonds that hold tRNA molecules in the correct three-dimensional shape are
Hydrogen bonds
29
Because the bacterial cell’s DNA is not surrounded by a nuclear envelope
Coupled transcription and translation occurs
30
The type of point mutation that results in a premature stop codon is called a
Nonsense mutation
31
Gene expression is
The process by which DNA directs the synthesis of proteins
32
Eukaryotic processing of the primary transcript includes
The addition of a 5’ cap, a 3’ Poly-A tail, and the splicing out of introns
33
What is an example of a post-translational modification of a polypeptide?
Cleavage of a polypeptide into two or more chains
34
Nonsense mutations can
Also change a codon for an amino acid into a stop codon
Causes translation to be terminated early
Resulting polypeptide will be shorter than regular
Lead to nonfunctional proteins
35
In eukaryotic cells, a __ by a __ targets a growing peptide to the ER
Signal peptide
| Signal-recognition particle
36
What best describes the arrangement of generic information in a DNA molecule?
The three-nucleotide words of a gene are arranged in a non overlapping series on the DNA template strand
37
Transcription is
The synthesis of RNA using information in the DNA
38
Insertions and deletions are called
Frameshift mutations
39
What is a key difference in gene expression between eukaryotic and prokaryotic cells?
In prokaryotic cells, the mRNA transcript is immediately available as mRNA without processing
40
Who made the one gene-one enzyme hypothesis?
Beadle and Tatum
41
What catalyzes the linkage between ribonucleotides to form RNA during gene expression?
RNA polymerase
42
Gene expression
Process by which DNA directs synthesis of proteins
43
One gene-one enzyme hypothesis
Function of a gene is to dictate the production of a specific enzyme
44
Genes provide
Instructions for making specific proteins, but do not directly build proteins
45
RNA has
Uracil instead of T
| Single stranded
46
DNA protein requires
Transcription and translation
47
Transcription
Synthesis of RNA using information in the DNA
Two nucleic acids (DNA&RNA) are written in different forms of the same language. Information is transcribed, rewritten, from DNA to RNA
48
DNA strand can
Serve as a template for assembling a complementary sequence of RNA nucleotides
49
Messenger RNA (mRNA)
Transcript of the gene’s protein building instructions
| Carries a generic message from the DNA to the protein synthesizing machinery of the cell
50
Transcription is
The general term for synthesis of any kind of RNA on a DNA template
51
Translation
Synthesis of a polypeptide using the information in the mRNA
52
During this, the cell translates
The nucleotide sequence of an mRNA molecule into an amino acid sequence of a polypeptide
53
Ribosomes are
The sites of translation, molecular complexes that facilitate the orderly linking of amino acids into polypeptide chains
54
Bacteria cell
Allows translation of mRNA to begin while is transcription is still in progress
55
Eukaryotic cell
Nuclear envelope separates transcription from translation in space and time
56
Transcription occurs
In nucleus before RNA transcripts can leave the nucleus, they’re modified to produce mRNA
mRNA then transported to the cytoplasm
57
Primary transcript
Initial RNA transcript from any gene
58
Genes program
Protein synthesis via genetic messages in the form of messenger RNA
DNA RNA protein
59
Triplet code
Generic instructions for a polypeptide chain are written in the DNA as a series of nonoverlapping, 3 nucleotide words
Transcribed into complementary series of nonoverlapping, 3 nucleotide words in mRNA, then into a chain of amino acids
60
Template strand
For each gene, only one of 2 DNA strands is transcribed, provides the pattern (template) for the sequence of nucleotides in an RNA transcript
61
During transcription, the gene determines the
Sequence of nucleotide bases along the length of the RNA molecule that is being synthesized
62
Codons
RNA nucleotide triplets, written in 5-3 direction
63
An mRNA molecule is complementary rather than identical to its DNA template because
RNA nucleotides are assembled on the template according to base pairing rules
64
The term codon is also used for
The DNA triplets along the nontemplate strand
65
Reading frame
Correct groupings
66
mRNA, carrier of information from DNA to the cell’s protein synthesizing machinery
Transcribed from the template strand of a gene
67
RNA polymerase pries
The two strands of DNA part and joins together RNA nucleotides complementary to the DNA template strand, elongating the RNA polynucleotide
Assembles a polynucleotide only in its 5-3 direction
Can start a chain and initiates transcription
68
Bacteria, the sequence that signals the end of transcription is called
Terminator
69
Transcription unit
Stretch of DNA to un stream from the promoter that it transcribed into an RNA molecule
70
Start point
The nucleotide where RNA synthesis actually begins
Promoter of a gene includes within it in the transcription and extends several dozen or more nucleotide pairs upstream from the start point
71
Eukaryotic transcription factors
Mediate the binding of RNA polymerase and the initiation of transcription
72
Transcription initiation complex
Whole complex of transcription factors and RNA polymerase Is bound to the promoter
73
TATA box
Shows the role of transcription factors and a crucial promoter DNA sequence
74
RNA polymerase moves along the DNA
Untwists the double helix
| Enzyme adds nucleotides to the 3 end of the growing RNA molecule as it continues along the double helix
75
Bacteria transcription proceeds through
A terminator sequence in the DNA
76
RNA processing
Both ends of the primary transcript are altered
77
Poly A tail
At 3 end, enzyme adds 59-250 more nucleotides
78
RNA splicing
Removal of large portions of the RNA molecule that is initially synthesized
79
Introns
Noncoding segments of nucleic acids that lie between coding regions
80
Exons
Other regions, they are eventually expressed, usually by being translated into amino acid sequences
81
Spliceosome
Small RNAs and proteins, large complex
Binds to several short nucleotide sequences along an intron, including key sequences at each end
Intron released and spliceosome joins together 2 exons
82
Ribozymes
RNA molecules that function as enzymes
83
Alternative RNA splicing
Genes can give rise to 2 or more different polypeptides, depending on when segments are treated as exons
84
Domains
Proteins often have a molecular architecture consisting of discrete structural and functional regions
85
Exon shuffling
The presence of introns in a gene may facilitate the evolution of a new and potentially beneficial proteins
86
Transfer RNA
The translator, series of codons along an mRNA molecule
Functions to transfer amino acids from the cytoplasmic pool of amino acids to a growing polypeptide in a ribosome
Each tRNA molecule translates a given mRNA coding into a certain amino acid
87
Anticodon
Nucleotide triplet that basa pairs to a specific mRNA codon
88
tRNA molecules are transcribed from
DNA templates
89
Aminoacyl-tRNA synthetases
Correct matching up of tRNA and amino acid is carried
90
Wobble
Flexible base pairing at this codon position
91
Ribosomal RNAs (rRNA)
A ribosome that consists of a large subunit, each made up of proteins and one or more
Most abundant type
92
P site (Peptidyl-tRNA binding site)
Holds the tRNA carrying the growing polypeptide chain, while the A site (aminoacyl-tRNA binding site) holds the tRNA carrying the next amino acid to be added to the chain
93
Discharged tRNAs leave the ribosome from the
E site
94
Signal peptide
Targets the protein to the ER
| the polypeptides of proteins destined for the endomembrane sytem or for secretion are marked by
95
Signal recognition particle
Protein RNA complex
96
Polyribosomes (polysomes)
Strings of ribosomes
| Enable a cell to make many copies of a polypeptide very quickly
97
Mutations
Changes to genetic information, responsible for diversity
98
Point mutation
Chanda in a single nucleotide pair of a gene
99
Small-scale mutations
Single nucleotide pair substitutions
Nucleotide pair insertions or deletions
Can involve 1 or 2 pairs
100
Nucleotide pair substitution
Replacement of one nucleotide and its partner with another pair of nucleotides
101
Silent mutation
Change in nucleotide pair that may transform one codon into another that is translated into the same amino acid
Has no observant effect on the phenotype
Can occur outside genes as well
102
Missense mutations
Substitutions that change one amino acid to another
| Little effect on the protein
103
Nonsense mutations
Point mutation that can also change a codon for an amino acid into a stop codon
Causes translation to end prematurely
Resulting polypeptide will be shorter than the polypeptide encoded by the normal gene
Lead to nonfunctional proteins
104
Insertions and deletions are
Additions or losses of nucleotide pairs in a gene
Often have a disastrous effect on resulting protein more often than substitutions do
Alter the reading frame of the generic message, the triplet grouping of nucleotides on the mRNA that’s read during translation
Frameshift mutation
105
Frameshift mutation
Occurs whenever the number of nucleotides inserted or deleted is not a multiple of 3
Protein almost certain to be nonfunctional, unless frameshift very near end of gene
106
Mutagens
Physical and chemical agents that cause mutations
107
A gene is a region of DNA that can be expressed to
Produce a final functional product that is either a polypeptide or an RNA molecule
108
Transcription into RNA then
Translation into a polypeptide that forms a protein or specific structure and function
109
Ribozymes are
Catalytic RNA molecules that function as enzymes
110
3 properties of RNA that enable it to function as an enzyme
Can form 3 dimensional structure because of its ability to base pair with itself
Some bases in RNA contain functional groups that may participate in catalysis
RNA may H-bond with their nucleic acid molecules
111
Some introns contain sequences that
May regulate gene expression
112
Alternative RNA splicing
Some genes can encode more than one kind of polypeptide, depending on which segments are treated as exons during splicing
113
Domains
Discrete regions
| Proteins often have a modular architecture consisting of discrete regions
114
Different exons code for
Different proteins
115
Translation is
mRNA to protein
116
tRNA helps
Cell translate an mRNA message into protein
Transfers amino acids
Carries anticodon
117
Accurate translation
Correct match between tRNA and an amino acid, done by the enzyme aninoacyl tRNA synthetase
Correct match between the tRNA anticodon and mRNA codon
118
Gene determines
Primary structure, and primary structure determines shape
119
Bacteria transcription/translation
Can happen at the same time
120
In eukaryotic cells, the nuclear envelope separates
Transcription/translation
121
Point mutations
Chemical changes in just one base pair of a gene
Change of single nucleotide in a DNA template strand can lead to production of abnormal protein
Once mutation occurs, usually stays
122
Nucleotide pair replaces
One nucleotide and its partner with another pair of nucleotides
123
Missense mutation
Still codes for an amino acid, but not the correct amino acid
124
Silent mutation
No effect on the amino acid produced by a codon because of the redundancy of the genetic code
125
Nonsense mutation
Change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein
126
Insertion/deletion
May alter the reading frame-frameshift mutation
Disastrous effect on the resulting protein more often than substitutions do
Additions or losses of nucleotide pairs in a gene
127
Possibility of amino acid changes
Maybe changes the secondary and tertiary, definitely changes the primary
128
Spontaneous mutations can occur during DNA replication, recombination, or repair
.
129
Gene is
A discrete unit of inheritance, region of DNA that can be expressed to produce a final functional product that is either a polypeptide or an RNA molecule
130
Coding segments are
Exons
