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chapter 17- transcription and translation Flashcards

1
Q

proteins are the link between what aspects of genes

A

genotype and phenotype

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2
Q

what are the two stages of gene expression

A

transcription and translation

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3
Q

what does one gene code for

A

one polypeptide

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4
Q

what does transcription produce

A

messenger rna

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5
Q

where does translation occur

A

ribosomes

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6
Q

in eukaryotic cells can translation occur while transcription happens

A

no the nuclear envelope prevents this by separating the two processes

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7
Q

once transcription is done can translation start immediately

A

no the mrna is modified through rna processing to make the finished mrna

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8
Q

what is the primary transcript

A

initial rna transcript before processing

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9
Q

where does rna processing occur

A

nucleus

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10
Q

what is the triplet code

A

three nucleotide “words” that are transcribed into mrna triplet code and then into amino acids

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11
Q

what is the template strand

A

template of gene sequence
always the same strand for a given gene

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12
Q

what are codons

A

mrna base triplets
each codon codes for a specific amino acid

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13
Q

what do codons do

A

they are read in the 5’ to 3’ direction to indicate which amino acid to add to the polypeptide chain

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14
Q

how many codons are there and the categories

A

64 codons
1 start
3 stop
61 for amino acids

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15
Q

what is the start codon

A

AUG

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16
Q

what does rna polymerase do

A

separates dna strands and joins together rna nucleotides resulting in a complementary strand
does not need primer

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17
Q

what is the promoter

A

the sequence where rna polymerase attaches

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18
Q

what is the terminator

A

the sequence that signals the end of transcription

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19
Q

what is the transcription unit

A

dna stretch that was transcribed

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20
Q

what are the three steps of transcription

A

initiation
elongation
termination

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21
Q

what starts initiation in transcription

A

promoters will signal the start point
transcription factors help the binding of rna polymerase

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22
Q

what is the transcription initiation complex

A

completed assembly of the transcription factors and rna polymerase

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23
Q

which promoter is used for the initiation complex in eukaryotes

A

TATA box

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24
Q

what happens during the elongation step of transcription

A

rna polymerase untwists the double helix 10-20 bases at a time and adds the rna nucleotides 5’ to 3’

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25
what are the steps of termination in transcription in eukaryotes
rna polymerase transcribes a polyadenylation signal sequence and the strand is released 10-35 nucleotides past this sequence
26
what happens during rna processing
some interior parts and cut out and the pieces and rejoined the 5' end gets a modified nucleotide 5' cap the 3' end gets a poly-A tail
27
what constitutes the 5' cap
a modified guanine nucleotide
28
what is a poly-A tail
50-250 adenine nucleotides
29
why does rna processing happen
facilitates mrna export protects mrna from hydrolytic enzymes helps ribosomes attach to 5' end
30
what is the point of cutting the mrna
takes out the noncoding regions (introns) and only leaves the exons (coding regions)
31
what does the rna splicing
spliceosomes (many proteins and small nuclear ribonucleoproteins (snRNP) that recognize splice sites)
32
what do the rnas in the spliceosomes do
catalyze the splicing reaction
33
what are ribozymes
catalytic rna molecules that function as enzymes
34
what are three properties of rna that allow it to function as an enzyme
can form 3D structures because it can base pair with itself contains functional groups that can participate in catalysis can hydrogen bond with other nucleic acid molecules
35
what can introns contain
sequences that can regulate gene expression
36
what is alternative rna splicing
genes encoding for more than one polypeptide depending on which segments are treated as exons during splicing
37
what is the result of alternative rna splicing
more proteins can be made than the number of genes
38
what does transfer rna do
transfer amino acids to a polypeptide in a ribosome
39
structure of trna
not all identical 80 nucleotides long specific amino acid on one end anticodon that matches the amino acid on the other end which base pairs with a complimentary codon on mrna
40
how can trna bind to more than one codon
wobble: flexible pairing at the third base of a codon
41
how does a trna get an amino acid
aminoacyl-trna synthetase joins them the synthetase is amino acid specific and trna specific (must have correct codon)
42
structure of ribosome
large subunit with binding sites A and P and exit site E and a small subunit with the mrna binding site
43
names of A and P sites
peptidyl-trna binding site aminoacyl-trna binding site
44
what are the three steps of translation
initiation elongation termination
45
what happens in translation initiation
mrna trna and two ribosomal subunits are brought together small ribosomal subunit binds to the mrna and a special initiator trna subunit moves along the strand until it finds the start codon initiation factors bring in the large subunit
46
what is the translation initiation complex
small and large subunits mrna and first trna
47
what happens during elongation translation
amino acids are added one by one at the c terminus (carboxyl) of the chain involves elongation factors (proteins)
48
what are the three steps of the amino acid addition in translation (elongation) and which steps take energy
codon recognition (E required) peptide bond formation translocation (E required)
49
what are the steps of termination in translation
stop codon reaches A site A site accepts a release factor (protein) which causes the addition of a water molecule (hydrolysis)
50
why are polypeptides modified after synthesis
can be needed to become fully functional
51
what are the two types of ribosomes
free floating bound to ER
52
what do free ribosomes make
cytosol proteins
53
what do bound ribosomes make
endomembrane system and secreted proteins
54
are bound and free ribosomes forever that way
no they are identical and can switch from one to the other
55
what does a signal peptide do
attached at the amino terminus and signals that the polypeptide is destined for the ER or for secretion
56
what happens if a signal peptide is present on a polypeptide
a signal recognition particle (SRP) will bind to the signal peptide and bring the peptide and the ribosome to the ER
57
what is a polyribosome/polysome
multiple ribosomes translating a singular mrna at the same time
58
what are mutations
changes in the genetic material of a cell or virus
59
what are point mutations
changes to a singular base pair of a gene
60
if a mutation has a harmful effect on the phenotype it is called
a genetic disorder or hereditary disease
61
point mutations are divided into two categories
nucleotide pair substitutions one or more nucleotide pair insertions/deletions
62
what are the three types of nucleotide pair substitution and what are they
silent mutations: switch between 2 codons but no effect because the codons code for the same amino acid missense mutations: wrong amino acid is coded nonsense mutations: amino acid becomes a stop codon -> nonfunctional protein because missing the rest of it
63
what do insertions/deletions result in
frameshift mutation
64
what is the result of a frameshift mutation
disastrous effect on resulting protein
65
what are mutagens
physical/chemical agents that can cause mutations

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