Module 2 Flashcards
(256 cards)
1
Q
What is linkage?
A
- genes on the same chromosome may not undergo independant assortment
2
Q
What does crossing over do?
A
- allow recombinant types to be produced
3
Q
What is crossing over?
A
- physical exchange of genetic material
4
Q
What is the relationship between recombination and distance between genes?
A
- directly proportional
- further apart= less recombo
5
Q
What is map distance?
A
- numerically = to the percentage of recomination between loci (recombo frequency)
6
Q
What are the steps to map distance determination?
A
- obtain heterozygous f1
- testcross hetero f1 to homo recessive
- phenotype of f2 tells you genotype of f1 gamete
7
Q
What is a non-recombinant?
A
- og gene
- parent
8
Q
What is the map distance formula?
A
( # recombinants / total) x100
9
Q
Does crossing over affect random segregation?
A
- no
10
Q
Can recombo exceed 50%?
A
no
11
Q
What happens as genes get further apart?
A
- crossing over starts to get more and more underestimated
(higher than 25)
12
Q
Who discovered cytological evidence for crossing over?
A
- Barbara McClintoc and Harriet creighton discovered crossing over does involve a physical exchange btwn homologs
13
Q
What is the method for determining 3 loci crossing over?
A
- create an individual who is heterozygous for 3 genes
- test cross to see the frequency of each gamete type
- pair up data (put progeny in groups by pairing up opposite alleles (ATE and ate)
- identify no cross-overs and double cross-overs (no cross = most common and double cross = least common)
- determine gene order ) compare DCO, NCO genes that switched is in middle)
- classify progeny types based on type of crossover (single, double, none)
- determine map distances
14
Q
What is the coefficient of coincidence?
A
how many DCOs will we actually see
15
Q
What is the coefficient of coincidence formula?
A
-observed DCOs/ expected DCOs
- expected DCO = distances multiplied
- inference = 1-c
16
Q
What is reverse mapping?
A
- predicting based on linked loci
- linked alleles are more likely to be same gamete
17
Q
What are the reverse mapping formulas?
A
- crossing over: 1/2 distance (bc crossing over creates 2 gametes)
- non CO: (1-distance) /2
18
Q
What is the likelihood of crossing over?
A
- more crossover the furthest apart
- most likely:
NCO
SCO large distance
SCO small distance
DCO
19
Q
What are the forms of gene mapping?
A
- linkage
- reverse mapping
- pedigree analysis
- genome-wide association studies
20
Q
What is a pedigree analysis for gene mapping?
A
- observe multiple families and find associated traits
21
Q
What are genome-wide association studies?
A
- uses single nucleotide polymorphism variations at a single base in the DNA
- studies populations not pedigrees, you don’t have to be related
- looks for associations between a a trait and SNP across the genome
22
Q
What are the steps to genome-wide association studies?
A
- collect samples from 2 groups
- genotype each sample at 100,000 sites (SNPs)
- analyze data to see if SNPs are found more frequently in 1 group vs another
- if SNP is associated it may be linked (close to a disease gene)
23
Q
What did miescher do?
A
- isolated DNA from WBCs
- called it nucleon
- noted it was slightly acidic and high in phosphorus
24
Q
What did kossel do?
A
- said DNA has four bases Adenine, guanine, cytosine, thymine
25
What did phoebus levene do?
- dna is made of nucleotides, said it was in a diamond,
- knew phosphate and sugar base made nucleotide
26
What were the genetic material theories?
-protein as genetic material
- nucleic acid as dna
27
Why was protein thought to be genetic material?
- 1/2 the weight of cell
- lots of variation
- structure of nucleic acid was too simple to account for
- necessary variability
- many researchers were just interested in transmission genetics so it was just accepted without being tested
28
who discovered transformatiom
griffith
29
What experiment proved dna as genetic material?
- labeled protein and dna separately using radioactive materials, protein by s and DNA by p
- infected with E. Coli, mi, detect where there is radioactivity
- if it was in protein it wouldn't move if in dna it would move through the generations of particles
- labeled DNA found in progeny phasis
30
Are DNA and proteins colinear?
yes
31
What is the central dogma of genetic materials?
- DNA is transcribed into RNA
- RNA is translated to protein, creates constant amino acid chain
- DNA is replicated and transferred to daughter cell
- DNA function is carried out by proteins
- some viruses have RNA and not DNA (persist in RNA state)
- viruses can do reverse transcription and go from RNA to DNA or another RNA molecule
32
What did Rosalind franklin do?
- used x-ray to discover DNA is helical, has repeated units, and saw different spacing proving helical structure
33
What shows the shape of DNA?
- crystallization and defraction
34
What is chargaffs rule?
- proportions of bases are =
- A = T
- C = G
- but proportions of A and T and C and G don't have to be equal
35
What is watson and cricks dna structure model?
- base pairing between two strands of nucleotides allows for constant width of the helix and agrees with chargeoffs base composition rule
- dna is made of a sugar and a phosphate
- H on 2' in DNA
- OH on 2' in RNA
- 1' attaches to base
- 3' joins f 5' of next nucleotide
- 5' attaches phosphate
36
What are the groups of nitrogenous bases?
- purines and pyrimidines
37
What are purines?
A
G
38
what are pyrimidines
C
t in dna
u in RNA
39
What is a nucleoside?
sugar and base
40
What is a nucleotide?
sugar, base, phosphate
41
What are the nucleotide bondings?
- A and T pair with 2 H bonds
- C and G pair with 2 h bonds
- h bonds are weak so they aren't the major force holding it together
42
What is polemization of nucleotides?
- phosphodiester bonds connect sugar phosphate backbone
- 3' end on 1 nucleotide bonds to 5' end of next one
- antiparallel
43
What charge does DNA hae?
negative
44
Where are DNA's hydrophobic bases?
in center
45
Where is DNAs hydrophillic backbone?
facing outside
46
Can DNA's plectonic coil be pulled apart?
no
47
What kind of grooves does DNA have?
- major and minor
48
What stabilizes DNA and holds it together?
- base stacking maximizes hydrophobic interactions and is main force in stabilizing double heliz
- H is really just for bonding specificity
49
What are the secondary DNA structures?
- phosphate is always on outside
- B form
- A form
- Z form
50
What is B DNA form?
- most relivant, right handed, watson and crick model
51
What is A DNA form?
more compact form
52
What is Z dna form?
- left hand
- zig zag
53
Which way does DNA primarily go?
to the right
54
How is DNA analyzed?
- electrophoresis
- quantification using UV light
55
What does electrophoresis do?
- seperates DNA fragments
56
How does electrophoresis work?
- fragments migrate from - to +
- smaller pieces go further
- not a linear relationship (inversely proportional to log)
57
How does quantification using UV light work?
- uv absorbed by ring structures in bases
- relative max is around 260 nm and absorbtion increases by 40% when DNA is denatured
58
What is Denaturing of DNA?
- breaking H bonds and hydrophobic interactions with heat or chemically allowing 2 strands to separate
59
What is hyperchromic effect?
- increase in UV absorbtion due to denaturation
- exposed bases absorb more UV
60
What is the DNA melting curve?
- shows Tm and possible molecular configurations for various stages of melting
61
What is Tm?
- mid point of denaturation
- 50% denatured
- higher CG = higher Tm
62
What is TMV packaging?
- RNA virus
- each layer has 17 identical proteins
- develops helical structure as RNA and proteins interact
63
What are bacteriophage lambda virus DNA packaging steps?
1. terminase binds viral genome
2. terminase DNA binds procapsid portal
3. DNA translocation into capsule
4. contamer clevage and packaging completion
64
Can e. coli shrink DNA?
yes
65
How much dna does the human body have?
- around 50 trillion cells and around 100 meters of DNA
- each diploid cell has around 2 m DNA with chromosome 1 being the largest
66
What is chromatin?
- complex of DNA chromosomal proteins, RNA within nucleus
67
What is euchromating>
- lighter staining
- less dense
- part of chromosome during interphase
- actively transcribes genes
- condenses and relax/ stretches out
68
What is heterochromatin?
- darker staining parts of chromosome
- fewer genes transcribed
- tightly condensed
- usuallly not a part of crossing over
- replicates less in S phase
69
What is consecutive heterochromatin?
always heterochromatic/ tightly condensed with like centromeres
70
What is facultative heterochromatin?
maybe euchromatic sometimes (x-chromosome barr body)
71
What is Chromatin strucutre?
1. first compaction: DNA wrapped twice around a nucleosome
2, We know beads are wrapped around themselves
3. compressed nucleosomes into loops
4. loops of loops
72
What are nucleosomes?
- core of 8 histones and 53 bp linker DNA
73
What are histones?
- basic proteins and have lots of + charged amino acids
- allows electrostatic bonding to negatively charged phosphates in DNA
- highly conserved -98%
- allows for adaptation by dying off of mutants
74
What is 11nm chromatin?
- tandem nucleosomes; beads on a string
75
What is a nucleosome core?
- core histones with around 147 bp DNA
76
What are the core histones?
- 2 H2A
- 2 H2B
- 2 H3
- 2 H4
77
How many bases are there per nucleosome?
200
78
How are nucleosomes arranged ?
- zig- zag twisting ribbon
79
How long are chromatin strands?
- 5-24 nm
- in vivo-model is smaller
80
How is chromatin organized?
- chromatin strands are closer in mitotic cells, mitotic chromosomes are most highly organized
81
What is nuclear matrix?
- fibrous network athroughout the nucleus that anchors a series of DNA loops
82
What induces DNA super coiling?
- torsional stress
83
What is supercoiling?
- when DNA coils back on itself when its overwound or underwound
84
What is + supercoiling?
- over-rotated in same direction as DNA coil so left-handed supercoil compensates
85
What is - supercoiling?
- DNA is underowund so right handed supercoil compensates
86
What does tropoisomerase do?
- alters DNA by cutting DNA backbone
- typically removes supercoiling
- important to replication and transcription
87
What are chromosome bonds?
- are charecteristic for a strain of organism and can be used to identify specific chromosomes
88
What is endopolypolidy?
- several rounds of DNA replication without seperation of replicated chromosomes
89
What are puffs?
white areas in DNA
- opposite of bands
- transcription is more likely to happen here
- looser coiled; euchromatin
90
What are centromeres?
- must attach to a spindle fibers for proper segregation into daughter cells
- heterochromatic
91
What identifies centromeres?
- histones
92
Do centromeres have specific sequences or conserved DNA sequences?
no
93
What do telomeres do?
- provide stability for ends of chromosomes so that chromosomes aren't degraded by exonucleases
- prevent chromosomes from joining with each other at the ends of ligase activity and caps them
- provides propper replication end of chromosome
- have GC pairs toward end of crhomosome
- have t-loop structure
- displaced strands are protected by proteins
94
What is a t- loop strucutre?
- repeated strucutre of GC overhangs and connects with another part of chromosme
95
What are the theories for DNA replication?
- conservative
- dispersive
- semiconservative
96
What is the conservative theory of replication?
- 1 strand is maintained, and we always get double stranded products from that
97
What is the dispersive theory for replication?
- both new strands have old and new parts and gets diluted as you go along
98
What is the semiconservative process of DNA replication?
- conserve q strand, dilute one strand
- correct method
99
What is the procedure for testing DNA replicaiton?
1. grow e. coli in media for many gens (sample dna)
2. transfer cells to different media (from heavy N to light N)
3. let replicate for 1 gen (sample DNA
4. Replicate 3rd time (sample DNA)
5. analyze with density gradient centrifusion
100
What did taylor, woods, and hughes do?
- visualize chromosmes using audiography during replication
- used H labeled Thymine
- allowed 1 round of replication with thymine and saw offspring
- allowed unlabeled replication and saw if thymine was still present
-saw 1 had thymidine and one did not proving sister chromatid exchange and crossing over occurs
101
What is the semi conservative process for dna replicaiton?
- old strand is template for direct synthesis of complementary strand
- result is 1/2 old dna and 1/2 new dna
102
What are the models for dna replication?
- theta replication
- rolling circle replication
- linear eukaryotic replication
103
What do all models of semi-conservative replication have in common?
- all replication starts and replication and proceeds until replicon is replicated
104
What is a replicon?
- unit being replicated together
105
What is theta replication?
- bacteria and other circular DNA molecules
- can happen from both directions
- bilateral replication
106
What is rollng circle replication?
- F factor and some viruses
- replication happens many times producing many strands as templates
107
What is linear eukaryotic replication?
- eukaryotic chromosomes have many replication origins along length
- multiple origins start at different times
- bidirectional from each origin
- 2 replication forks
- ends have unique procedure
- replicons are 20,000 - 300,000 bp long
108
What does DNA polymerase 3 do?
- does most DNA synthesis
- proofs 3' 5' exonuclease activity
109
What does DNA polymerase 1 do?
- discovered first
- 5'- 3' exonuclease activity to remove RNA primers
- proofs 3'-5" with exonclease activity
110
What does DNA polymerase do?
add to 3' end because 3' has OH
111
How is replication studied?
- with conditional mutants
- add or change proteins to see effcets
112
What catalyzes replicaiton?
- DNA polymerase
- phosphodiester needs nucleoside triphosphates
113
What way does any polymerase add?
5' - 3'
114
What is the leading strand associated with?
continous replication
115
What is lagging strand associated with?
- discontinuous replication
116
What are the parts of theta replication?
- 1 origin
- 2 lagging and 2 leading strands
117
What are the parts to rolling circle replication?
- 1 origin
- 1 leading and 1 lagging strand
- f factor from bacterial conjucation
- newly synthesized DNA is brown
118
What are the parts of linear replicaiton?
- 2 origins
- 2 leading and 2 lagging strands
119
What is the initation of the replication process?
- initiator protein DNAA binds to origin causing local unwinding and a short stretch of single strand DNA
120
What causes DNA unwinding?
- Helicase
- SSB
- gyrase
121
What does helicase do?
- attaches at replication fork and moves into fork, breaking H-bonds as the replication fork moves along DNA
122
What is Single stranded binding proteins?
- single stranded binding proteins coat single stranded DNA to protect, stabilize it, prevent double stranded DNA (hairpins)
123
What is gyrase?
topoisomerase that relieves supercoiling ahead of replication fork
124
What is topoisomerase?
- nicks DNA to relieve tension from supercoiling
125
What must DNA polymerase have?
- 3' OH that they can add nucleotides
126
What are RNA primers made by?
- primase, an RNA polymerase
127
How does DNA elongation work?
- DNA polymerase 3 adds nucleotides to the primer
- segment of RNA primer is eventually removed and replaced with DNA
- DNA polymerase 1 removes primers and fills in gaps
- DNA ligase seals nicks
128
what is a nick?
- a missing sugar -phosphate bond
129
What is a primosome?
helicase and primase
130
How many origins of replication do eukaryotes have?
many
- origin must be liscensed for replication to occur
131
Do eukaryotes have telomeres or polymerase?
- yes lots of telomeres and polymersase to replicate
132
What follows replication in eukaryotes?
- nucleosome assembly immediately follows replication
133
What does liscensing do?
- it makes sure each peice of each chromosome is only replicated 1 per cell division
134
What is replication liscensing factor?
- attaches to each origin of replication early in cell cylce
135
Where does replication start?
- only at licensed origins, as replication proceeds from origin licensing factor is removed
136
When is licensing factor activated?
- just after mitosis and before replication starts in cell cycle so it wont be put back on an origin until early next cycle
137
What do prokaryotes have?
- core enzymes
- haloenzymes
- sigma factors
- concensus sequences
138
What is a core enzyme?
- where transcriptin starts
139
What is a haloenzyme?
- core enzyme and sigma factor
140
What are the steps to prokaryote trancription?
1. template binding
2. chain initiation
3. chain elongation
4. chain termination
141
What is the sigma factor?
- tells core enzymes where to bind
142
What is a consensus sequence?
- a sequence that describes nucleotides most often present in a segment of interest
- implies there is an important function associated with sequence since it doesn't change overtime as much as other sequences
143
What does upstream mean?
- sequences prior to start of transcription
144
What does down stream mean?
- sequences after start of transciption
145
What are the control regions of transcription?
- prinbow/tata box = -10
- 5' 5a5aa5 -3' = -10
- -35 control region/consensus sequence
146
Where are control regions located?
in prokaryotic promotor
147
Where does transcription start
at +1 nucleotide
148
Where do the last primers take place?
- 70-100 nucleotides from the end in eukaryotes
- means there is no free 3' OH in this region for DNA polymerase to start from
- most cells skrink and die because of this
149
What is tolemerase?
- extends telomere by containing RNA to make repeats of DNA to exted 3" end of telomere
-RNA is used as template for DNA synthesis. After several nucleotides added telomerase moves along DNA and more nucleotides added. Eventually telomerase is removed
150
Where is tolomerase found?
- usually in sex cells but also in cancers
151
Do we transcribe everything?
no
152
What is transcription?
- synthesis of RNA
153
- what is the template for transcription
DNA
154
Does transcription need a primer?
no
155
How are RNTPs added in transcription?
5' to 3'
- uracil goes with adenine not thymine
- 2 phosphate groups are cleared from incoming rNTPs as nucleotide is added
156
What kind of mrna do prokaryotes have?
polycistronic
156
Do prokaryotes have introns?
no
157
What kind of MRNA do eukaryotes have?
- monocistronic
158
Do eukaryotes have introns?
yes
159
What must every transcribed gene have?
a promotor
160
Where does transcription start?
- the promotor
161
What is the trancription format of RNA?
- RNA is only single stranded so only 1 dna strand is copied
162
What is a template?
- the strand of DNA transcribed
163
What is the non-template/ coding strand?
- info used to copy template strand
- same code
164
Does it matter which DNA strand is copied?
yes
165
Does the initiation of RNA synthesis need a primer?
no
166
Where are new nuclotides added?
3' end
167
Does DNA rewind?
yes dna unwinds then reqindsd
168
How can different genes be transcribed?
- different genes can be transcribed from different strands of same DNA segment
- however if a gene starts at the top strand it always starts at the top strand
169
What is a transcription unit?
- segment of DNA that codes for an RNA molecule and sequences necessary for transcription
170
Is the promotor transcribed?
no
171
Where does RNA polymerase bind to DNA?
- at consensus sequences found in promotor so its at the start site of transcription
172
What are the - 10 tata box and - 35 consensus equences recognized by?
sigma subunit
173
174
What happens if a consensus sequence changes
RNA polymerase can't bind
175
How does bacteria transcription occur?
- core enyme and sigma associate bind to promoter
- dna strands seperate and form transcription bubble
- sigma dissociates after 9-12 nucleotides are joined to form RNA
176
Which way does elongation go?
- 5/- 3' using only core enzyme
177
Where does transcription stop?
a hairpin
178
What is a hairpin?
where RNA folds in on itself
- hairpins repeat
179
What is a direct repeat?
- same order
180
What is an inverted repeat?
- ACUUCA
181
What kind of repeat causes a hairpin?
- inverted
182
What are the kinds of hairpins?
- rho-independent
- rho
183
How does a rho independendent hairpin work?
- inverted repeats are also where DNA stops transcription
- these form stem-loop structures in RNA that signal termination
AU bonds are weaker and allow for dissociaiton of DNA RNA pairing
184
How does a rho hairpin work?
- rho binds RNA then moes toward 3' end and RNA polymerase
- RNA polymerase pauses at the termination hairpin
- rho has helicase activity that causes RNA DNA hybrid to unwind and transcription ends
185
How many times can a peice of DNA be simultaneously transcribe into many copies of RNA?
- 1 peice of DNA can simultaneously be transcribed into many copies of RNA
186
What does RNA polymerase 1 do?
-transcribes ribosomal RNA and larger RNA
187
What does RNA polymerase 2 do?
transcribes messenger RNA and snRNA
188
What does RNA polymerase 3 do?
transcribes small ribosomal and transfer RNA
189
How are the RNA polymerases different?
- each polymerase binds to a different promotor, transcription factor and termination factor
190
Where does transcription take place in eukaryotes?
nucleus
191
Where does transcription take place in prokaryotes
cytoplasm
192
What is hnRNA?
- heterozygous RNA = pre mrna
193
What is pmrna?
-precursor for MRNA and primary transcript for MRNA
- pre-mrna
194
How does RNA polymerase 1 work?
- RNA to 1prRNA and then undergoes processing to release S rRNA
- several tandem copies of rRNA genes
195
What are cis elements?
- close to coding region of a gene and help determine when gene should be transcribed
- binding site for proteins (RNAs)
196
What are trans elements?
- proteins or RNA from other genes, attaches to cis-elements or other transcription factors, recruits RNA polymerase
197
What is the core/basal promoter?
- immediately upstream of gene and where basal transcription apparatus binds
- has tata box
198
Where is the regulatory promotor?
- immediately upstream of core promotor
- variety of consensus sequences
199
What is the initiation complex?
- ordered assembly process begins with transcription factors binding at tata box
- transcription factors and activators bind to transcription factor binding sites (enhancers) and bring those regions close to area of transcription
200
How does elongation occur?
- after around 30 bp are synthesized RNA polymerase leaves promotor and begins elongation
transcription bubble contains 8 bp of DNA-RNA hybrid
- structure of RNA polymerase causes seperation of newly formed RNA strand from DNA template strand
201
What occurs with RNA polymerase 2?
- has its own helicase activity to unqind incoming DNA exposing template strand
- clevage of RNA occurs based on a consensus sequence
- Rat 1 binds and degrades trailing RNA
202
How is pmrna transferred to mrna?
3 types:
- capping of 5'
- poly A tail added to 3'
- removal of introns
203
What happens at polymerase 3?
- small transcripts
- promotors can be located within gene
- number and position of internal promotor elements (boxes) vary from gene to gene
- transcription factors interact with these internal promotor elements and with polymerase to position polymerase for proper initiation of trancriptoon at +1 nucleotide
204
What are the differences between prokaryotic and eukaryotic trascription?
- transcription and processing in nucleus, translation in cytoplasm in eukaryotes
- processing in eukaryotes only
- eukaryotes have different RNA polymerase for different types of RNA
- some viruses only have RNA replication
205
What are ribosomes?
- complex of RNAs and protein
- 2 subunits in fully assembled ribosomes
- most abundant kind of RNA
- doesn't fully assemble until translation
206
What are the unusual trna bases?
- ribothymine
- pseudoridine
- inosine
207
What is ribothymine?
- thymine with ribose attached
208
What is pseudoridine?
ribose attaches to 5 on ring instead of 1
209
What is inosine?
- derivative of guanine
- can bind to many bases
210
What structure does TRNA have?
clover leaf
211
Can trna bases be modified?
- yes
212
When does capping occur in pmrna?
- as soon as 5" end of prmrna is free of RNA polymerase
213
What is the importance of capping?
- gives mRNA stability
- aids RNA in splicing efficacy
- aids in translation efficacy since cap protein binding proteins bind to cap and ribosome binds to cap-binding proteins
214
What is the importance of tails?
- protects mRNA
- length determines stability
- shortens when mrna ages
- initiates translation by helping ribosome attach to mRNA
- termination of transcription
- tail added after cleavage
215
What is a plicosome?
- snRNPs and pmrna complex, structure where introns are removed and exons are joined together
216
What are SnRNPs?
- small nuclear ribonucleic proteins, starts with U
217
What are snrnas?
- have regions complementary to ends of axons, sites in introns or sites on other snRNAs
218
What is required for splicing?
- critical sequence at 5' splice site, 3' splice site and branch pt within an intron
- specific bases code for splicing
219
What is the splicing procedure?
- cleavage at 5', loop it around, release
220
What happens if pmrna undergos different splicing methods?
-results in different functional mrnas
221
What were the RNA interference experiments?
- injected double-stranded DNA into worm
- saw genes with nucleotide sequence that was the same as injected RNA has decreased expression
- can silence target gene by mRNA degradation and or inhibiting translation
- interference censors oour own genes
222
What is RNAI?
- process of destroying/ shutting off gene expression using double-stranded RNAs
- cleaved by dicer to form in RNAs
- miRNAs and siRNAs bind and form RNA induced silencing complex (RISC( that base paires with miRNA and inhibits translation
- miRNA transcribed by a distinct gene and targets other genes
- siRNA comes from mRNA and transopsons or viral RNA and targets genes it comes from
223
Are crispr changes permanent?
- yes, daughter cells will have changed dna
224
Which RNAs are translated?
only mrna
225
What is the protein structure?
- amino acids joined by peptides
226
Which way to proteins go?
from n to c
227
How is a secondary structure produced?
- chain of amino acids folds in on itself to produce 2ndary structure (alpha helix and beta pleated sheets)
- if it folds again its tertiary
228
What is a quaternary protein?
- If it has more than 1 subunit
229
What did Crick do for genetic code?
- proposed a nonoverlapping code
230
What did Brenner and crick do for genetic code?
- codon consists of 3 non-overlapping nucleotides
231
What is the genetic code?
- need a 3 letter codon to prove for all 20 amino acids if not overlapping
- if overlapping than proteins= sequence would be restricted to which AA could be adjacent to each other
- if they overlapped there would be way too many AA
232
What is a triplet code?
- three reading frames
- dna is double stranded so 6 reading frames
233
What does a correct reading frame have?
- start and stop codons
234
How many codons are there?
61
235
What is the start codon?
aug
236
Describe the coding language?
- unambiguos
- degenerate
- start and stop punctuation
- no internal punctiation
- almost universal
237
What does a wobble cause?
- a single trna can pair with more than 1 codon
- must be third codon
238
What is an anticodon wobble?
- a signle trna with guanine in first andicodon (5' end) will bp with 2 different codons
- I is onl in TRNA and anticodons
239
What are the steps to translation?
1. charging
2. initiaton/ building of a ribosome
3. elongation
4. termination
240
What does elongation of translation require?
- translocation of a ribosome requires GTP (energy) and elongation factor
241
What are polysomes?
- multiple ribosomes translating same mRNA simultaneously
242
How does termination of translation work?
- stop codon arrives at A site
- release factor binds to stop codon
- protein is released from P site
- gtp is converted to GDP and P
243
What is the A site?
aminoacyl
244
What is the P site?
- peptidyl site
- initiatior trna occupies P site
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What is the e site?
exit
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What sites can hold TRNA
APE
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What is 23s rrna?
- large subunit that acts as ribozyme to form peptide bonds between AA
- peptidyl transferase activity
- part of initiation of translation
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What is initation of translation?
- BP between shine-delgarno sequence of MRNA and small ribosomal subunit
- small subunit binds first
- BP between AUG on MRNA andantidcodon on TRNA
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What is charging of translation?
- aminoacyl synthelase for each AA (can recognize all TRNAs for that AA)
- AA carboxyl end is joined to 3' end of TRNA
- Shrine-delgarno sequence is at 5'
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What is polycistronic mRNA?
- 1 RNA molecule is produced, but it contains info for more than 1 gene product
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How is initiation of translation different in eukaryotes?
- small subunit of ribosome, initiation factors, and charged initiaor trna recognize and bind to cap mRNA
- initiation complex moves down mRNA until it finds first AUG codon
- tail on MRNA interacts with proteins to bind 5' cap to enhanve ribosomal binding forming loop structure
- more and different initiaton factors
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What surrounds the AUG codon?
- kozac sequence
253
How are elongation and termination different in eukaryotes?
- more and different EF and TFs
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