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BI157 > Chapter 17 > Flashcards

Chapter 17 Flashcards

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1
Q

What is gene expression?

A

a process in which DNA directs the synthesis of proteins

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2
Q

What is the one gene-one enzyme hypothesis?

A

a gene dictates the production of a specific enzyme

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3
Q

What is the one gene-one polypeptide hypothesis? (2)

A

Some proteins are not enzymes

Some proteins are made up of multiple polypeptides with different genes

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4
Q

What is transcription? (3)

A

Synthesis of RNA using the information in the DNA

Two nucleic acids are written in different forms of the same language

Information is transcribed from DNA to RNA

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5
Q

Messenger RNA

A

Carries a genetic message from the DNA to the protein-syntehsizing machinery of the cell

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6
Q

What is translation? (2)

A

Synthesis of polypeptides using the information in the mRNA

Cell must translate the nucleotide sequence of an mRNA into the amino acid sequence of a polypeptide

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7
Q

What are ribosomes? (2)

A

sites of translation

facilitates the orderly linking of amino acids into polypeptide chains

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8
Q

Bacteria vs Eukaryote gene expression (3)

A

Bacterial DNA is not separated by nuclear membranes from ribosomes

allows translation and transcription to occur at the same time

eukaryotic cells transcript first in the nucleus, transport into the cytoplasm where it translates

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9
Q

What is pre-mRNA?

A

RNA transcripts that are modified into mRNA

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10
Q

What is primary transcript?

A

Initial transcript from any gene that is not translated into a protein

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11
Q

What is the triplet flow? (4)

A

genetic instructions for a polypeptide chain are written in the DNA as a series of three-nucleotide words

series of nucleotides is transcribed into three specific orders, which is then translated

gene determines the sequence of nucleotide bases along the length of the RNA being synthesizes

for each gene, only one strand of DNA is transcribed

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12
Q

What is the template strand? (3)

A

DNA strand being transcribed

the same strand is used as the template every time for a given gene

synthesized in an antiparallel direction to the template strand

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13
Q

What are codons?

A

mRNA nucleotide triplet written in teh 5’ > 3’ direction

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14
Q

Coding strand (2)

A

non-template strand is identical to codons but with T instead of YOU

during translation, it is read in the 5’ > 3’ direction

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15
Q

What are codons for? (5)

A

64 exists

61 of them are designated for amino acids

3 are termination codons

AUG acts as a start signal and codes for methionine

enzymes can remove methionine

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16
Q

What is the reading frame?

A

Correct groupings of symbols for an intended language

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17
Q

What are the stages of transcription?

A

Initiation, elongation, and termination

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18
Q

What is RNA polymerase? (4)

A

An enzyme that pries two strands of DNA apart and joins together RNA nucleotides complementary to the DNA template strand

Bacteria have one type

Eukayrotes have at least three

do not need primers

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19
Q

What is a promoter?

A

DNA sequence where RNA polymerase attaches and initiates transcription

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20
Q

What is a terminator?

A

A squence that signals the end of transcription

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21
Q

What is a transcription unit?

A

A stretch fo DNA downstream from the promoter that is transcribed into an RNA molecule

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22
Q

What is the start point?

A

The nucleotide where RNA synthesis begins

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23
Q

What is the transcription factor? (3)

A

Mediates the binding of RNA polymerase and the initiation of transcription

after transcription factors attach to the promoter, the RNA polymerase 2 binds to it

forms the transcription initiaition complex

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24
Q

TATA box (2)

A

nucleotide sequence containing TATA upstream around 25 nucleotides from the start point

once the transcription factors bind to the TATA box, polymerase can bind to it

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25
Elongation process
When the RNA polymerase moves along the DNA, and the new RNA molecule peels away
26
Termination in Bacteria (2)
Transcription proceeds through a terminator sequence in the DNA terminator functions as the termination signal, requiring no further modification before translation
27
Termination in eukaryotes (4)
Transcribes a polyadenylation signal (AAUAA) in the pre-mRNA once it appears, it is immediately bound by certain proteins in the nucleus proteins cut it free from the polymerase, releasing the pre-mRNA RNA polymerase continues to transcribe until enzymes catch up and dissociates it
28
What is RNA processing? (2)
Enzymes in the eukaryotic nucleus modify pre-mRNA in specific ways before genetic message I dispatched to the cytoplasm both ends are altered and some inner sections are cut out
29
How is mRNA altered? (2)
5' end receives a 5' cap, a modified form of guanine added to the first 20-40 nucleotide 3' end adds adenine to form a poly-A tail
30
What is the mRNA ends for? (30
Facilitate export of the mature mRNA from the nucleus helps protect the mRNA from degradation by hydrolytic enzymes helps ribosomes attach to the 5' end of mRNA
31
What is RNA splicing?
Removal of large portions of the RNA moleculues
32
What are introns?
Noncoding segments of nucleic acid that lie between coding regions
33
What are exons?
epxressed regions of the nucleic acids
34
What is UTR
Part of the mRNA that will not be translated but help ribosome binding
35
How does RNA get spliced?
Introns get cut out and exons get joined together
36
What are spliceosomes?
A complex of proteins and small RNA that removes introns
37
What are ribozymes?
RNA molecules that function as enzymes introns can function as ribozymes, catalyzing its own excision
38
How can RNA enable some RNA molecules to function as enzymes? (3)
Because it is single-stranded, a region of an RNA molecule may base-pair in an antiparallel arrangement with a complementary region elsewhere, forming a 3d structure like an enzyme Some of the bases in RNA contain functional groups that can participate in catalysis ability of RNA to hydrogen bond with other nucleic acid molecules add specificity to its catalytic activity
39
Why are introns important? (3)
A single gene can encode more than one kind of polypeptide depends on which segments are treated as exons (alternative RNA splicing) allows humans to work with small numbers of genes
40
What are domains? (3)
Discrete structural and functional regions of proteins one domain can act as an active site, while another binds to a cellular membrane different exons code for different domains
41
What is exon shuffling?
Introns can facilitate the evolution of new and potentially beneficial proteins
42
What is transfer RNA (tRNA)?
Translator that reads a series of codons along an mRNA molecule and transfers amino acids from the cytoplasmic pool of amino acids to a growing polypeptide in a ribosome
43
What are ribosomes? (2)
Structures made of proteins and RNA Adds each amino acid brought to it by tRNA to the growing end of a polypeptide chain
44
How is tRNA used in translation? (5)
Reads a nucleic word (the mRNA codon) and interprets it as a protein word (the amino acids) bears a specific amino acid at one end bears a nucleotide triplet that can base-pair with the complementary codon on mRNA consists of a single RNA strand, smaller than mRNA Can fold itself and form a 3d structure, and twists into an L shape
45
What is an anticodon? (4)
A nucleotide triplet that base-pairs to a specific mRNA codon example- mRNA codon 5'-GGC-3' (code for glycine) tRNA base-pairs with 3'-CCG-5' as its anticodon carries glycine at the other end
46
Where is tRNA transcribed? (3)
From DNA templates made in the. nucleus and travels to the cytoplasm used repeatedly
47
What is molecular recognition?
tRNA that binds to an mRNA codon must carry that amino acid, carried out by aminoacyl-tRNA synthetases Pairing of tRNA anticodon with the appropriate mRNA codon some tRNA are able to bind to more than one codon
48
What are aminoacyl0tRNA synthetases? (2)
Enzyme that only fits a specific combination of amino acid and tRNA catalyzes covalent attachment of amino acid to its tRNA
49
What is wobble? (2)
flexible base pairing at specific codon positions YOU at the 5' end of tRNA can pair with A or G in the 3' end
50
What are ribosomes used for? (2)
facilitates the specific coupling of tRNA anticodons with mRNA codons during protein synthesis Holds the tRNA and mRNA close together and catalyzes the formation of peptide bonds
51
What are ribosomes made up of? (2)
A large and small subunit that joins when attached to an mRNA molecule subunits are made up of ribosomal RNA 1/3 is made up of proteins found in the exterior
52
Ribosomal RNA (2)
made in the nucleolus most abundant type of RNA
53
What do proteins on ribosomes do?
Support shape changes
54
How do bacterial and eukaryotic ribosomes differ? (2)
Eukaryotic ribosomes are larger some drugs can inactivate bacterial ribosomes without affecting eukaryotic ribosomes
55
What is the ribosome structure? (2)
a binding site for mRNA and three sites for tRNA an exit site in the large subunit where the polypeptide leaves
56
What are the three binding sites for tRNA in ribosomes?
P site holds the tRNA carrying the growing polypeptide chain A site holds the tRNA carrying the next amino acid after the P site E site is where discharged tRNA leaves the ribosomes
57
What occurs during translation initiation?
mRNA, tRNA with the first amino acid, and subunits come together ribosomal subunit binds to both mRNA and a specific initiator tRNA (carries methionine)
58
How does the translation stage differ in eukaryotes?
small subunits is bound to the tRNA and binds to the 5' cap f mRNA. Moves downstream until it reaches the start codon
59
What is the translation initiation complex? (2)
union of all the RNA and ribosomes formed by GTP hydrolysis
60
What are initiation factors?
proteins required to bring all the components together
61
What occurs during translation elongtaion?
Amino acids are added one by one codon recognition occurs peptide bond formation occurs translocation occurs
62
What is codon recognition? (2)
Anticodon of an incoming tRNA pairs with the complementary mRNA in the A site GTP increases accuracy and efficiency
63
What is peptide bond formation? (2)
rRNA in the large subunit catalyzes formation of a peptide bond between amino groups of the A site and P site removes polypeptide from the tRNA in the P site
64
What is translocation?
ribosomes translocates the tRNA in the A site to the P site, P site to the E site where it is removed
65
What occurs during termination translation? (3)
When ribosomes reach a stop codon on mRNA, A site accepts a release factor release factor promotes hydrolysis of the bond between the tRNA in the P site and the last amino acid of the polypeptide two ribosomal subunits and other components dissociate
66
How do proteins fold?
gene determines primary structure, folding proteins
67
What is post translational modification? (3)
certain amino acids being chemically modified by the addition of sugars, lipids, phosphate groups, and more enzymes removes amino acids from the leading end can also cleave
68
What is the difference between free and bound ribosomes? (2)
Free ribosomes synthesize proteins that stay in the cytosol bound ribosomes are attached to the ER< and makes proteins of the endomembrane system and proteins secreted from the cell
69
How are polypeptides synthesized? (9)
Growing polypeptide either completes in the cytosol or cues the ribosome to attach to the ER Polypeptides for attached RNA are marked by signal peptide Recognized by a signal-recognition particle (SRP) SRP brings the ribosome to a receptor protein built into the ER Membrane SRP then binds to a receptor protein in the ER forms a protein complex that forms a pore and ahs a signal-cleaving enzyme SRP leaves, polypeptide synthesis resumes, and translocates across the membrane signal cleaving enzymes cuts off the signal peptide rest of the completed polypeptide leaves the ribosome and fold into its final conformation
70
How are signal proteins for organelles apart from the endomembrane system formed?
Translation is completed in the cytosol before being imported to said organelles
71
How are multiple polypeptides made? (3)
Multiple ribosomes translate an mRNA at the same time a single mRNA can be used to simultaneously make many copies (forms polyribosomes/ polysomes)
72
What is a mutation? (2)
Changes to the genetic information of a cell responsible for the diversity of genes
73
What is point mutation? (2)
changes in a single nucleotide pairs of a gene if it occurs in the gamete, it may be transmitted to offspring and future generation
74
What is a genetic disorder? (2)
a point mutation producing an adverse effect example- sickle cell disease
75
What is nucleotide-pair substitution? (2)
Replacement of one nucleotide and its partner with another pair of nucleotides some can have no effect due to the redundancy of genetic code
76
What is silent mutation? (2)
Mutation with no observable effect on phenotype example- change in nucleotide pair changes codon but translates into the same amino acids
77
Missense mutation
substitutions that changes one amino acid to anther
78
What is nonsense mutation? (2)
mutation that changes a codon for an amino acid into a stop codon terminates translation prematurely and produces a short polypeptide
79
What is an insertion?
Additions of nucleotide pairs in a gene
80
What is a deletion?
Loss of nucleotide pairs in a gnene
81
What is the consequence of deletion and insertions? (2)
Bothe produces a more disastrous effect compared to substitution may alter the reading frame of the genetic message
82
What is a frameshift mutation? (2)
whenever the number of nucleotides inserted or deleted is not a multiple of three all downstream nucleotides are improperly grouped
83
What is spontaneous mutation?
When a mismatched nucleotide strand is used as a template in the next round of replciation
84
What is a mutagen? (2)
Interacts with DNA and causes mutation example- radiation
85
What are chemical mutagens? (3)
Can be similar to DNA nucleotide, pairs incorrectly can interfere with correct DNA replication and distorts the DNA double helix can change pairing properties of bases
86
What is a gene?
a region of DNA that can be expressed to produce a final functional product that is either a polypeptide or an RNA molecule

BI157 (21 decks)

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