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Genetics Test 3 > Lecture 25 > Flashcards

Lecture 25 Flashcards

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1
Q

rRNA cell type

A

prokaryotic

eukarytoic

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2
Q

rRNA is…

A

ribosomal RNA

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3
Q

rRNA function

A

structural and functional componenets of the ribosome

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4
Q

mRNA is…

A

messenger RNA

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5
Q

mRNA cell type

A

prokaryotic

eukaryotic

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6
Q

mRNA function

A

carries genetic code for proteins

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7
Q

tRNA is..

A

transfer RNA

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8
Q

tRNA cell type

A

prokaryotic

eukaryotic

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9
Q

tRNA function

A

helps incorporate amino acids into polypetide chain

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10
Q

snRNA is…

A

small nuclear RNA

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11
Q

snRNA cell type

A

eukaryotic

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12
Q

snRNA function

A

processing of pre-mRNA

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13
Q

snoRNA is…

A

small nucleolar RNA

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14
Q

snoRNA cell type

A

eukaryotic

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15
Q

snoRNA function

A

processing and assembly of rRNA

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16
Q

miRNA is…

A

micro RNA

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17
Q

miRNA cell type

A

eukaryotic

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18
Q

miRNA function

A

inhibits translation of mRNA

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19
Q

siRNA is…

A

small interfering RNA

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20
Q

siRNA cell type

A

eukaryotic

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21
Q

siRNA function

A

triggers degradation of other RNA moelcules

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22
Q

piRNA is

A

piwi-interacting RNA

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23
Q

piRNA cell type

A

eukaryotic

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24
Q

piRNA function

A

suppresses the transcription of transposable elements in reproductive cells

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25
crRNA is...
CRISPR RNA
26
crRNA cell type
prokaryotic
27
crRNA function
assists destruction of foreign DNA
28
lncRNA is...
long noncoding RNA
29
lncRNA cell type
eukaryotic
30
lncRNA function
variety
31
ribosome
- complex of rRNAs and protein - 2 subunits - does not fully assemble until translation
32
describe prokaryotic ribosome
70S large 50S small 30S
33
describe eukaryotic ribosome
80S large 60S small 40S
34
unit for ribosome size
Svedberg units | based on migration using velocity centrifugation
35
Why do the subunits size not add to get the full ribosome size?
the unit is based on migration which depends on size, density, and conformation not just molecular weight
36
large prokaryotic ribosome subunit
23 S rRNA 5 S rRNA 31 proteins
37
small prokaryotic ribosome subunit
15 S rRNA | 21 proteins
38
snoRNA is important...
in isolating the individual rRNAs form the initial transcript this is a type of RNA processing
39
precursor rRNA
contains all rRNA except 5s rRNA in eukaryotes
40
Describe processing for rRNA with snoRNA
1. Methylation occurs to precursor rRNA and identifies separate rRNA-to-be molecules - spacer sequences are not methylated 2. Pre-rRNA is cleaved to produce distinct molecules occurs in the nucleolus this process occurs in both pro and eukaryotes but there is no nucleolus or snoRNAs in prokaryotes
41
Where do snoRNA come from
- sometimes transcribed from own genes by RNA pol II or pol III - sometimes come from intron areas of pre-mRNA molecules
42
how does tRNA get its secondary structure?
base pairing
43
describe tRNA processing
- initial transcript contains several tRNA molecules - tRNAs are separated - 5' and 3' ends are trimmed - intron is removed in eukaryotes - it can now take its cloverleaf secondary structure - 3' end is modified by a CCA addition in eukaryotes - some bases are modified to get the tRNA in its final L-shaped structure
44
anticodon is...
located next to the intron which will be removed during tRNA processing
45
5'-CCA-3'
sequence added to the 3' end of tRNA during processing
46
inosine
- unusual base found in tRNA - derivative of guanine - so is purine - found at 5' end of anticodon when present - pairs with adenine, uracil, and cytosine - impacts translation
47
pseudouridine
- similar to uracil turned sideways | - attaches to ribose at the 5 position of pseudouridine ring rather than 1 position
48
dihydrouridine
- similar to uracil | - normal double bond between 5 and 6 is saturated so there is a single bond and extra hydrogen molecules
49
What are the unusual bases in tRNA
- inosine - pseudouridine - dihydrouridine
50
tRNA is responsible for...
binding to an amino acid and bringing the amino acid to the ribosome for incorporation into a protein
51
acceptor stem
3' end of tRNA | amino acid binds to the 3' end of tRNA
52
variable loop
between the anticodon loop and T loop on tRNA varies in size between different tRNA molecules
53
the components of tRNA
cloverleaf structure with intrastrand complementary pairing on 4 stems ``` results in… D loop T loop anticodon loop variable loop ```
54
how is the final structure of tRNA formed
areas of D and T loop of the cloverleaf secondary structure pair up causing a twisted helical, L-shaped structure
55
3 types of processing to convert pre-mRNA into mature mRNA
- addition of 5' cap - 3' cleavage and addition of polyA tail - RNA splicing
56
capping the RNA - processing mRNA
occurs as soon as 5' end of pre-mRNA is free of RNA polymerase gives stability aids in splicing efficiency aids in translation efficiency since cap binding proteins bind to the cap and the ribosome binds to cap-binding proteins
57
describe capping the RNA in processing of mRNA
- 1 phosphate is removed from 5'end of RNA - guanine nucleoside tri-P is added in 5'-5' linkage - methyl groups are added to position 7 on guanine ring and to 2' position of sugar of the next 2 nucleotide
58
Why is mRNA capped and not tRNA?
cap is important in allowing mRNA to bind to ribosome for translation
59
Importance of polya tail
- protects the mRNA - helps initiate translation - involved in termination of translation
60
how does the poly-A tail protect mRNA
- tail length determines stability - when too short, the mRNA is recycled - tail shortens as mRNA ages
61
how does the poly-A tail aid in translation?
helps attachment of ribosome to mRNA
62
The poly-A tail allows...
mRNA to exist for a longer time in the cytoplasm before it is degraded
63
describe the poly-A tail
50-250 adenine nucleotides are added to the 3' end by enzyme Poly(A) polymerase
64
spliceosome
snRNPs and pre-mRNA complex structure at which introns are removed and exons are joined together
65
splicing
removing the introns and joining the exons together occurs in spliceosome
66
snRNP
small nuclear ribonucleoproteins formed by small nuclear RNAs with proteins - complex of ~300 proteins + 5 snRNA uridine rich
67
snRNAs have regions complementary to...
small nuclear RNA the ends of exons, site within introns, or other snRNAs
68
What are the 3 basic signals for the spliceosome?
critical sequences at... - 5' slice site - 3' splice site - branch point within the intron
69
Base pairing between ___ is important to proper splicing
pre-mRNA and snRNA
70
Describe formation of poly A tail
- pre-mRNA is cleave 11-30 nts downstream from consensus sequence - adenine nucleotides are added to the 3' end by Poly(A) polymerase
71
In the process of cleavage and polyadenylation, pre-mRNA is cleaved after...
AAUAAA sequence and before GU-rich sequence in transcribed RNA
72
Splicing requires ___ and depends on ____.
requires precise excision of introns and joining of exons depends on key sequences at critical points
73
branch point
contains an adenine
74
In mRNA, the sequence containing the ends of the introns and include the adenine will read...
exon - GT...A...G - exon
75
Splicing process
1. U1 and U2 bind to the primary transcript 2. a complex of U4, U5, and U6 joins 3. cleavage occurs at 5' splice site allowing a lariat to form and release a complex of U1 and U4 4. a transesterification reaction occurs between the guanine at the 5' end of the intron and the adenine at the branch point 5. cleavage occurs at the 3' splice site and the exons are spliced together
76
U1 and U2
small ribonucleoproteins
77
where does U1 bind
5' splice site
78
where does U2 bind
branch site
79
what holds the splicesome together
the interaction between mRNA and snRNAs
80
snRNPs are critical in...
proper positioning for splicing base-pairing is important to the their binding to the RNA
81
Where are most conserved regions for splicing located?
in the intron
82
alternative splicing
a single pre-mRNA can undergo alternative splicing methods resulting in different functional mRNAs can differ tissue to tissue or individual to individual
83
describe alternative splicing
- allows one primary transcript to produce different proteins - the final mRNA may include all exons or only some of them
84
3' cleavage sites
- a primary transcript may have different cleavage sites at the 3' end - depending on which one is use, a different length product may form
85
Both ___ and ___ produce different mRNAs from a single pre-mRNA
alternate splicing multiple 3' cleavage sites
86
RNA editing
- occurs in some, but not all, mRNA sequences - type of posttranscriptional modification - not one of the 3 types of processing as it doesn't always occur - specific sequence changes that are made to RNA after transcription
87
RNA editing occurs in...
some nuclear RNA | more common in organelle RNA
88
How was RNA editing detected
- 1986 | - when the mRNA coding sequences of some genes were found to differ from the coding regions of the DNA they came form
89
most common types of RNA editing
- changes from cytosine to uracil - changes from adenine to inosine - inserting or deleting uracil residues
90
guide RNAs
aid in insertion and deletion types of RNA editing
91
describe guide RNA activity
- gRNA pairs with mRNA in an imperfect pairing - the gRNA acts as template for addition or deletion of bases - the mature mRNA is released - the mature mRNA will now have sequence different from the sequence coded by the DNA it came from
92
RNAi is...
RNA interference shuts off gene expression using dsRNA
93
Who received the Nobel prize for RNAi?
Fire and Mello
94
RNAi was discovered in...
C. elegans
95
How was RNAi discovered?
1. injected dsRNA into C.elegans 2. noticed genes with the same sequence as the injected RNA decreased expression - translation of the targeted genes was inhibited
96
How may RNAi be helpful?
may aid the cell by limiting the invasion of foreign genes may censor the expression of the cell's own genes
97
describe how RNAi works
1. dsRNA is cleaved by the enzyme dicer to form miRNA or siRNA that is ~21 nts long 2. these bind with proteins to form RNA induced silencing complex 3. this base pairs with mRNA and either inhibits translation or degrades mRNA
98
miRNA
transcribed from a distinct gene and targets other genes for regulation in RNAi activity it inhibits translation of the target gene
99
siRNA
comes from mRNA, transposons, or viral RNA and targets the genes it comes from in RNAi activity it degrades mRNA
100
RISC
RNA induced silencing complex base pairs with mRNA in RNAi activity to inhibit translation or degrade mRNA formed by either miRNA or siRNA binding with proteins
101
the small RNA involved in RNAi
siRNA | miRNA
102
potential issue with treating medically with RNAi
may target the expression of a similar gene sequence rather than only that of interest
103
RNAi has been tested in treatment of
- macular degeneration - study halted - cancer tumors - nerve disorders
104
CRISPR
clustered regularly interspaced palindromic repeats
105
CRISPR are in...
prokaryotes
106
CRISP is...
a prokaryotic mechanism to protein bacteria from foreingn DNA by cleaving invading DNA (phage, etc)
107
How may CRIPR be used
manipulation of the system may allow for editing of targeted areas of DNA

Genetics Test 3 (7 decks)

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