Unit 2- DNA and Gene Expression Flashcards
1
Q
Whose studies determined that DNA was the genetic material instead of Protein?
A
Griffin, Hershey and Chase
2
Q
Whose Research is this? What was the impact?
A
Griffith. He determined that DNA was the heritbale information in DNA because it was changed and reverted back to its original form.
3
Q
Whose work was this? What was the impact?
A
Hershey and Chase
4
Q
Who determined the structure and mechanism of replication of DNA?
A
Watson & Crick
Rosalind Franklin & Wilkins
5
Q
Building Blocks of DNA
A
Nucleotides
6
Q
Components of a Nucelotide
A
Deoxyribose
Phosphate
Nitrogenous Base (4 Different Types)
7
Q
Polarity of DNA
A
5’->3’
8
Q
Base Pairs in DNA
A
A:T G:C
9
Q
How many base pairs are in each turn of the Double helix?
A
10
10
Q
DNA Strands run _____ To each other
A
Antiparallel
11
Q
How much DNA is in a human cell
A
2m of DNA
12
Q
How large is a typical Cell?
A
20-40 Micrometers
13
Q
Packaged DNA consists of
A
Single Molecule of DNA+Associated Packaging proteins (Histones)+ Scaffolding Proteins
14
Q
Bacteria typically have _____, _____ chromosome.
A
Single, Circular
15
Q
Name This Image
A
Karyotype
16
Q
Each Chromosome is made up of
A
Single, long DNA Molecule+accompanying proteins (Chromatin)
17
Q
Karyotypes are arranged in what pattern?
A
From largest to smallest, except the sex chromosomes, which are always #23
18
Q
Functions of Chromosomes:
A
To Carry Genes
19
Q
Replication Origin
A
Sites Where Replication begins
20
Q
Telomeres
A
help overcome the End-Replication problem
21
Q
During Mitosos, DNA is compacted to what size?
A
~ 10,000-75000x
22
Q
During Interphase, DNA is compacted to what size?
A
~500-400x ( Less compacted than in mitosis)
23
Q
Nucleosome
A
Basic Unit of Eukaryotic Chromosomes that consist of a length of DNA coiled around a core of histones.
24
Q
Histone core of nucleosomes are made of
A
4 different Histone proteins
25
What is the function of Linker Histone H1
Helps pack nucleosome cores more tightly
26
Levels of Chromosome Packing
DNA-\> Nucleosomes
Nucleosomes (beads on a string) packaged into Chromatin Fiber
Chromatin Fiber packaged into folded loops
Folded loops packaged into Mitotic Chromosome
27
Chromatin-Remodeling Complexes
Use ATP to Change DNA POsition along Histone cores of nucleosome
Can make DNA More or less accessible
28
True or false: Chromatin-remodeling Complexes are actvated during mitosis
FALSE
29
Acetyl groups ___ chromatin, making it more accessible
Open
30
Histone Acetyl Transferases (HATs)
Add Acetyl Groups to Histones
31
Histone Deactylases (HDACs)
Remove Acetyl groups from histones
32
Specific combinations of modifications create docking sites for regulatory proteins that promote _______ or \_\_\_\_\_\_\_
Decondensation; condensation
33
Euchromatin
Regions or chromosome that are active and less condensed
34
Heterochromatin
Regions of chromosome that are not active and are more condensed
35
Regions of euchromatin and heterochromatin are regulated by what?
Histone Modifications
36
Histone Modifications promoting "Condense Me" signals may propagate along DNA until\_\_\_\_\_\_\_\_ is reached
Barrier Sequence
37
Errors in Genetic code
Mutations
38
Mutations are a basis of
Evolutionary change
39
Each strand of DNA serves as a ______ \_\_\_\_\_ for new complementary strand to be replicated
Template Strand
40
The Human Genome can be replicated in as little as
8 Hours
41
Semiconservative Replication
Since one sister strand of new daughter DNA molecules is new and one is old, mechanism of replication is called semiconservative.
42
Describe this process
Semiconservative DNA Replication
43
True or False: DNA Replication begins at only one site along eukaryotic chromosomes?
False
44
Replication Origins
Special Sequences of DNA that recruit initiator proteins to begin DNA replication Process
45
Replication Machine
The DNA Double Helix is opened and more proteins are recruited
46
Replication Fork
Y-Shaped Region along which new DNA strands are synthesized
47
Bidirectional replication
Since replication proceeds in both directions away from the replicaiton origin, the process is bidirectional.
48
Polymerization
Occurs by addition of nucleotide to 3' end of growing DNA molecule and 5' end of incoming nucleotide (Continues to grow in 5' to 3' direction)
49
DNA is replicated in opposite directions causing 1 strand to be ______ and another strand to be \_\_\_\_\_\_
Continuous ; Discontinuous
Or
Leading;Lagging
50
How is the discontinuously replicated strand produced?
Via Backstitching mechanism that allows for unidirectional addition of DNA Nucleotides in an overall bidirectional process
51
The continuously replicated strand is called the
Leading Strand
52
The discontinuously replicated strand is called the
Lagging strand
53
The small pieces of DNA replicated for discontinuous strand are called
Okazaki Fragments
54
True or False: Okazaki fragments remain disjointed.
FALSE: They are put together with DNA Ligase
55
What is the error rate of DNA Polymerase
~1 in 10^7 errors
56
How does DNA Polymerase maintain its low error rate (high fidelity)
Carefully monitoring base-pair before catalyzing nucleotide addition
Proofreading when mistake occurs
57
When does DNA Proofreading occur
Concurrently with DNA Synthesis
58
What does DNA Polymerase do if an error is detected?
The previously added base is removed and polymerase tries again
59
DNA Polymerase must attach to the 3' end of the template before
placing nucleotides
60
True or false: Primase has proofreading
FALSE
61
True or False: Chromatin-remodeling complexes are activated during Mitosis
False
62
What is the function of Nuclease?
Degrades RNA Primer
63
What is the function of Repair polymerase?
Makes DNA version of complementary strand
64
What is the function of DNA Ligase?
It links Okazaki fragments together.
65
What are some of the enzymes and proteins that come together to complete DNA Replication?
DNA Ligase
Single-Stranded Binding proteins
DNA Topoisomerases
Primase
Polymerase
Sliding Clamp
Clamp Loader
Repair Polymerase
DNA Ligase
66
What is the DNA End-Replication Problem?
As the Replication fork reaches the end of the lagging strand, there is not enough room to replace the final primer with DNA.
67
Telomeres
Long, repetitive sequences at the end of chromosomes that solve the DNA-End replication problem
68
Telomerase
The enzyme that maintains telomeres. It has a short stretch of RNA incorporated into enzyme that serves as template for the telomeric DNA
69
What are the types of DNA Damage?
Deamination
Depurination
Covalent Modifications (Thymine Dimers)
70
What types of DNA damage would result in a Double-Stranded break?
Radiation
Mishap at replication fork
Chemical assaults
71
What is the basic tool for DNA damage Repair
Excision Repair
72
Name 4 mehtods for DNA damage repair
Excision Repair
Mismatch Repair
Nonhomologous End-Joining
Homologous Recombination
73
What are the steps in a Mismatch DNA Repair?
Mistake is recognized
new vs. parental strand is determined
Portion of mutated strand is removed
Filled in by repair polymerase
74
What is Non-Homologous End Joining?
Double-Stranded break repair that occurs soon after the damage occurs. The Enzymes detect damage, "clean" the ends, and ligate them together
75
True or False: NHEJ will result in loss of some nucleotides
True
76
What is Homologous Recombination
A Double-Stranded Break Repair which the 5' ends of broken DNA are chewed back and DNA repair polymerase extends the broken strand.
77
What are the consequences of a lack of DNA Repair?
Mutation
Sickle-Cell Hemoglobin
Cancer
78
What is the Central Dogma of Molecular Biology?
DNA Serves as Template for RNA Production (transcription) and multiple RNAs function in making proteins (translation)
79
What is Gene Expression
Process whereby information in DNA is turned into useful product
80
True or False: The entire Genome is transcribed into RNA
False:
Entire genome is not transcribed into RNA and cell tightly controls how much of each type of RNA is made
81
What is the Nucleic Acid associated with RNA
Ribonucleotides (as opposed to Deoxyribonucleotides)
82
What are the Nucleotides associated with RNA (and their Base Pairs)
Adenine, Guanine, Cytosine, Uracil
83
True or False: RNA is Double-Stranded
False: RNA is single-Stranded
84
What are three types of functions that RNA's single-stranded properties result in?
Structural, Catalytic, and Regulatory functions
85
True or False: Transcription uses Helicase to open the DNA Strand
False: The DNA is opened, but there is no Helicase involved.
86
True or False: RNA transcription has a higher fildelity than DNA replication
False
87
Messenger RNAs (mRNA) Function
Code for Proteins
88
Ribosomal RNAs (rRNAs) function
Form the core of the ribosome's structure and catalyze protein synthesis
89
MicroRNAs (miRNAs) Function
Regulate Gene Expression
90
Transfer RNAs (tRNAs) function
Serves as adaptors between mRNA and Amino Acids during Protein Synthesis
91
Other Noncoding RNA Function
Used in RNA Splicing, gene regulation, telomere maintenance, and many other processes
92
Promoter's DNA sequence directs RNA Polymerase as to which DNA strand (does what)??
Serves as Template
93
What are the three types of RNA Polymerases in Eukaryotes?
RNA Polymerase I
RNA Polymerase II
RNA Polymerase III
94
What genes are transcribed by RNA Polymerase I?
Most rRNA genes
95
What genes are transcribed by RNA Polymerase II?
All protein-coding genes, MiRNA genes, plus all the genes for other Noncoding RNAs (Spliceosome)
96
What genes are transcribed by RNA Polymerase III?
tRNA Genes
55 rRNA Genes
Genes for many other small RNAs
97
What process begins when TBP/TFIID complex binds the TATA box of a gene?
RNA Polymerase II Transcription
98
What is a TATA Box?
A region of ~25 Bases upstream of transcription start site, made of many T & A Nucleotides
99
What is the Transcription Initiation Complex?
When the Binding of TBP/TFIID recruits the remaining general transcription factors and RNA Polymerase II
100
TFIIH
A kinase that's part of the Transcription Initiation Complex, which phosphorylates the tail of RNA Polymerase II
101
What 3 steps must be taken in order for the Pre-MRNA transcript to be processed into mRNA in the nucleus?
RNA Capping
Polyadenation
Splicing
102
What allows some processing proteins to assemble on RNA Polymerase II?
The Phosphorylation of the RNA Polymerase II Tail that allows this.
103
What is RNA Capping?
A Modified Guanine Nucleotide is added to the 5' end of a transcript shortly after transcription begins
Helps protect from Endogenous Nucleases
Helps Get translation started
104
What is Polyadenation?
A sequence within a transcript that tells RNA Polymerase II when to stop.
(Poly-A Signal)
105
What are Introns?
Regions that are not expressed as protein
106
What are Exons?
Regions of a gene that are expressed as protein
107
True or false: The number and length of introns and exons remains consistent.
False: the number and length of introns and exons varies from gene to gene.
108
RNA Splicing:
When Introns are spliced out of pre-MRNA, leaving the Exons behind to code for the protein
109
True or False: Sequence within Exons and Introns dictates boundaries of introns
TRUE
110
What is a Spliceosome?
A compltex of small Nuclear RNAs (snRNAs) and associated proteins (snRNPs) that are responsible for removing some introns
111
True or False: All introns are spliced with the Spliceosome.
False: Some introns are spliced by the spliceosome, but others are self-splicing
112
What are some examples of Alterations in splicing?
Exon Skipped
Alternative Exons
Introns Skipped
113
After processing, where is mRNA going to be exported to?
The Cytoplasm
114
Proteins that bind the 5' Cap, Poly-A Tail, and splice sites facilitate interaction with what area?
The Nuclear Pore Complexes.
115
mRNA Half-Life
The amount of time required for half the population of mRNA to be degraded
116
True or False: Every mRNA has the same Half-Life
False: Different mRNAs have different half-lives.
117
How is the mRNA's Half-Life determined?
By Specific sequences within mRNA, usually within the Untranslated Regions (UTRs)
118
What is the end result of Translation?
Proteins
119
What is the process of utilizing information in mRNA to produce Protein?
Translation
120
What is the Genetic Code?
The 4 different nucleotides that encode the 20 Amino Acids in groups of Non-Overlapping, 3-letter words (Codons)
121
122
True or False: Each codon is non-specific
False: Each codon is specific
123
True or False: There is redundancy among many of the codons
TRUE
124
How does the cell know where to start Translation?
There must be a Kozak Sequence and an AUG Start Codon
125
What sets the reading frame for translation?
The Kozak sequence and the AUG Start codon
126
True or False: Each Eukaryotic mRNA has more than one reading frame.
FALSE: There is only one reading frame. Finding the correct AUG to start is how to find it.
127
What is a point mutation?
Addition, Deletion, or Substitution of a single base
128
What types of mutations are frameshift mutations?
Additions and Deletions
129
What type of mutatation Substitutes one Amino Acid Codon for another Amino Acid's Codon
Missense Mutation
130
What type of Mutation substitutes an Amino Acid Codon with a Stop Codon
Nonsense Mutation
131
What type of mutation substitutes one Amino Acid Codon for the same Amino Acid Codon?
Silent Mutation
132
What type of mutation substitutes a Stop Codon with an Amino Acid Codon?
NonStop Mutation
133
When an Amino Acid is attached to a tRNA, what is it called
Aminoacyl-tRNA^AA
or
Charged tRNA
134
What shape are tRNAs typically in?
Cloverleaf shape
135
What are the two important sites (at opposite ends) of a tRNA molecule?
Anticodon
Amino Acid Attachment Site
136
What is tRNA Wobble?
It means there are not 61 different tRNAs in most species\*
137
WWhat are the 20 specific enzymes that match the specific Amino Acid with a specific tRNA?
Aminoacyl-tRNA Synthetases
138
What is used to create the high-energy bond between tRNA and the Amino Acid?
ATP
139
What are Ribosomes made out of
rRNA and Proteins
140
What are the two subunits of a Ribosome called?
Large (60s)
Small (20s)
come together to make (80s) when the ribosome is active)
141
What organelle is responsible for the process of translation?
Ribosomes
142
True or False: the Ribosome moves along the mRNA 3 codons at a time?
FALSE: They move along the mRNA one codon (3 nucleotides) at a time.
143
What are the three Binding sites for tRNA on the Ribosome?
A, P, E Sites
144
What is the definition and function of the A site on the Ribosome?
Aminoacyl-tRNA Binding Site
Accepts incoming tRNA
145
What is the definition and function of the P site on the Ribosome?
Peptidyl-tRNA Binding Site
Holds tRNA that is being attached to the growing polypeptide
146
What is the definition and function of the E site on the Ribosome?
Exit site (same answer for both)
147
Describe the Process of Translation in steps:
tRNA holding growing polypetide sits in P site •
A site, which had been empty, accepts incoming tRNAAA
• Ribozyme activity of rRNA forms peptide bond between last AA of growing polypeptide and incoming AA •
This severs connection between P site AA and its tRNA and at the same time, releases energy to power this process •
Large subunit shifts forward, shifting spent tRNA to E site and tRNA from A site to P site •
A site ready for next charged tRNA •
Continues until stop codon reaches A site
148
What Amino acid would the initiator tRNA carry?
Methionine (MET)
149
What are TIFs?
Translation initiation Factors
A group of proteins necessary for translation initiation
150
What makes the initiator tRNA unique?
It is able to bind to the P site, whereas the others can only initially bind to the A site.
151
Kozak Sequence Example
ACCAUGG
152
What is the initiator tRNA in Bacteria?
tRNA^fMET (F-Methionine)
153
True or False: Bacteria have a 5'cap to mediate small subunit and mRNA interaction.
FALSE
154
What is a Shine-Delgarno Sequence?
occurs just upstream of the AUG in Bacteria. It base-pairs with rRNA nucleotides, this positioning initiator tRNA at the P site.
155
How many coding sequences can a bacterial mRNA have?
156
How many coding sequences can a Eukaryotic mRNA have?
157
What are the three STOP Codons?
UAG, UGA, UAA
158
What happens when a Stop codon enters the A site?
Translation Termination
159
What does the release factor protein do in Translation?
It binds to teh A site, causing Ribosomes to add water molecule to peptidyl tRNA, resulting in a relase of the polypeptide chain
160
What is a Polyribosome?
When a single mRNA is translated by multiple ribosomes simultaneously
161
What is the end result of turning genes on and off or regulating gene expression?
Cell Differentiation
162
Complexes of mRNA with several accompanying ribosomes are called?
Polyribosomes/Polysomes
163
How long do proteins last?
A few moments, minutes, hours, days, months, or years.
164
How are proteins recucled?
A process called proteolysis
165
Describe the Proteolysis process
Enzymes that break down proteins, called proteases, break peptide bonds in the proteins.
166
A large, cylindrical complex of proteins that perform proteolysis in Eukaryotes
Proteasome
167
What do the ends of Proteasomes do?
They unfold the incoming proteins and feed linear polypeptide chain into the interior of the complex.
168
Inside the Proteasome, what do proteases do?
They break the protein into its individual Amino Acids
169
How are proteins targeted to a proteasome?
Ubiquitin
170
What is Ubiquitin?
A small polypeptide that when covalently bonded to protein functions to target that protein to the proteasome
171
In order for target protein destruction to occur, what must first happen?
Several Ubiquition molecules must be added to the protein
172
A Sequence of Amino Acids that function in targeting the protein for destruction
Degron
173
What are the Ubiquitin linked to on the target polypeptide?
The Lysine Residues
174
True or False: All genes within an organism have different DNA?
False: They all have the same DNA
175
How do cells have different functions?
Because they turn particular genes on or off.
176
What controls gene expression?
Signals from outside the cell:
Hormones, Tension of Substratum
177
True or False: Different cells respond in different ways to various signals
TRUE
178
What is the major mechanism for Gene Expression control?
Control of Transcription
179
What is the function of a Promoter in transcription?
To bind key transcription factors and RNA Polymerase
180
What binds other transcription regulators that control what happens at the promoter?
Regulatory DNA Sequences
181
What are the functions of Regulatory DNA Sequences?
May act as simple switches or in more complex ways
Sequences can be thousands of nucleotides away from transcription start site
Located nearby in bacteria, may be far away (distal) in eukaryotes
182
True or False:
Transcriptional Regulators have DNA Binding domains and regions that interact very unspecifically and weakly.
FALSE:
They interact very specifically and strongly
183
What are Transcriptional Switches?
They are switch-like (on-off) and allow the cell to respond to environmental cues.
184
In bacteria, what are the two switches which control several regulated genes/proteins?
Tryptophan Operon
Lac Operon
185
The Lac Operon is a _____ reaction
Catabolic (Breaks down)
186
The Tryptophan Operon is a _____ reaction
Anabolic
187
Transcriptional Activators
When activated, they turn the genes on or activate them
188
Transcriptional repressors
When activated, they turn the gene off or repress them.
189
How does the Tryptophan Operon work?
When Tryptophan is low, the operon is turned on due to the absence of the repressor at the regulatory seqence
190
When is the Tryptophan Operon repressed?
When the concentration of Tryptophan increases.
191
What are the steps of the Tryptophan Operon Repression?
The free Tryptophan binds the repressor and activates it, allowing it to bind to the DNA.
Binding to regulatory sequence blocks RNA polymerase from binding the Operon's promoter
Enzymes for tryptophan production are no longer expressed.
192
How does the Lac Operon work?
When Lactose is present and ATP is low, the Lac Operon will be turned On.
193
What operon controls the expression of genes required for breakdown of lactose to monosaccharides which can be used in cellular respiration?
Lac Operon
194
What are the differences between the Tryptophan and Lac Operons?
The Tryptophan is anabolic, Lac is catabolic
Tryptophan is controlled by a repressor, Lac has an activator and a repressor
195
Which Operon is controlled by an activator and a repressor?
Lac Operon
196
What is the Lac Operon's Repressor Called? How does it work?
Lac Repressor;
Repressor binds regulatory DNA (Operator) and will result in no gene expression.
197
What is the Lac Operon's Activator called? How does it work?
Cyclic AMP Activator (CAP Activator)
198
What is cAMP
Cyclic Adenosine Monophosphate
199
When is cAMP produced?
When ATP is low
200
When can the Cap Activator bind regulatory DNA?
Only if it is bound by cAMP
201
Once cAMP binds the CAP Activator, CAP binds DNA (at what site)\_\_\_\_\_ and can induce transription of the Lac Operon only if what?\_\_\_\_
CAP Binding Site
Only if it is not repressed by the LAC repressor.
202
In the Lac Operon, if there is a high concentration of Glucose and Lactose, will the operon be off or on?
Off
203
In the Lac Operon, if there is a high concentration of Glucose and a low concentration of Lactose, will the operon be off or on?
Off
Lactose is required to turn the Operon On
204
If there is a low concentration of Glucose and a low concentration of Lactose, will the Lac Operon be On or Off?
Off.
Lactose is required to turn the Operon On.
205
In the Lac Operon, if there is a low concentration of Glucose and a high concentration of Lactose, will the operon be off or on?
On.
If there is Low Glucose, there is low ATP.
If there is low ATP, then cAMP is activated. The Lactose will bind the repressor to remove it and transcription will occur.
206
What are regulatory sequences called in Eukaryotes
Enhancers
207
Where are enhancers located?
They can be thousands of nucleotides away from the transcription start site.
208
True or False:
Enhancers can only be upstream from the Transcription Start Site
False:
They can be upstream or downstream of Transcription start site
209
What is located between the enhancer and the Transcription start site?
The Spacer DNA
210
Interaction of enhancer sequence with Mediator Protein complex facilitates what?
Eukaryotic Transcription
211
Define Pluripotent
capable of giving rise to several different cell types.
212
How can cells be induced to de-differentiate?
By manipulating which transcription regulators are active or inactive.
213
What are the results of a cell being de-differentiated?
It results in loss of cell identity and a cell that can be potentially induced to become any other cell (iPS)
214
What is the result of Epigenetic control of Gene Expression?
Differentiated cells stay differentiated and so do their daughter cells due to the modifications to their chromatin.
215
Epigenetic modifications lead to what?
Cell Memory- an ability of cells to recall which genes they should express or not
216
How is Epigenetic control of gene expression regulated/mediated?
By positive feedback loops in which master gene regulators impact their own gene expression:
Gene A induces the Expression of Gene A
217
What is DNA Methylation?
What is the result of DNA Methylation?
Addition of methyl group on specific DNA bases (cytosine) results in silencing of that gene
218
True or False:
DNA Methlyation patterns are not passed from one generation to the next.
FALSE:
DNA methylation patterns are passed from one cell generation to next, including gametes in some instances
219
How do histone modifications impact chromatin structure?
It can create Euchromatin ( loosely packed) or Heterochromatin (tightly packed) chromatin which can result in a loss of gene expression
220
True or false:
Histone Modifications are passed from parent (cell) to offspring (cell).
TRUE
221
Define Epigenetic Inheritance
It means that a parent's experiences, in the form of epigenetic tags, can be passed down to future generations.
222
What is a method of Translational control in Prokaryotes?
Some bacteria express proteins that bind Shine-Delgarno sequence of prokaryotic mRNAs and thus block ribosome binding
223
What is a mechanism of Translational Control in Eukaryotes?
mRNAs may have regulatory sequences within their 5’UTR that impact 5’ cap from binding small ribosomal subunit
224
# Define:
Nonsense-Mediated Decay
Nonsense mutation will cause premature termination of translation and an incomplete polypeptide chain
225
How do Eukaryotic cells use Nonsense-Mediated Decay?
Eukaryotic cells use nonsense-mediated decay to destroy mRNAs containing premature stop codons
226
In mammals, how are premature stop codons detected?
By the Exon Junction Complex (EJC)
227
When is the EJC Deposited?
Wherever intron is removed from pre-mRNA, so each spliced mRNA has at least one complex bound to it
228
If mRNA contains a stop codon prior to the final EJC, what happens?
Translation is terminated and EJC does not get knocked off the mRNA
229
Define Nonstop Decay in Eukaryotes
Translation stalls when the ribosome reaches the end of transcript that lacks a stop codon
230
Nonstop Decay (process)
RNA degrading enzyme binds empty A site of ribosome and degrades the defective mRNA
231
Define a nonstop decay in Bacteria
Transfer Messenger RNA (tmRNA) binds the A site and directs the addition of amino acids that target the protein for destruction
232
Regulatory RNAs are part of what RNA family?
The Noncoding RNA
233
What are the three types of Regulatory RNA found to regulate gene expression at the post-transcriptional level?
MicroRNAs (miRNAs)
Small Interfering RNAs (siRNAs)
Long Noncoding RNAs (lncRNAs)
234
How are Micro RNAs expressed?
As part of longer RNAs, sometimes as part of introns and exons of other mRNAs
235
True or False:
MicroRNAs (miRNAs) must be processed by Dicer)
True
236
Define RISC
RNA-Induced Silencing Complex
237
True or False:
MicroRNA (miRNAs) do not have to integrate with RISC in order to function.
False:
Must integrate with RISC (RNA-induced silencing complex) in order to function
238
How do MicroRNAs (miRNAs) function?
Base-pair with target mRNAs and inhibit expression of target
•Exact, complementary match = target mRNA for immediate destruction
High degree complementary match = sequestration in cell away from translation machinery, eventual degradation
239
True or False:
MicroRNAs (miRNAs) are an inefficient way to control several related genes.
FALSE:
It is very efficient because there are several targets possible if the mRNAs all share the target sequence, which would be ideal for targeting several related genes.
240
Describe this process
miRNA processing beginning in mRNA and ending in mRNA degrading or sequestering and eventual degrading.
241
What is the Cell's defense mechanism that eliminates foreign RNAs (i.e. Viral RNAs)
RNA Interference (RNAi)
242
What is dsRNA?
Forms the genetic material of some viruses (double-stranded RNA viruses). Double-stranded RNA such as viral RNA or siRNA can trigger RNA interference in eukaryotes, as well as interferon response in vertebrates
243
How does Dicer process dsRNA?
It generates ssRNA ~22 base pieces (small interfering RNAs, siRNAs) which integrate with RISC and then target viral RNAs for destruction
244
What are siRNAs? what is their function?
Small Interfering RNAs, which integrate with RISC and then target viral RNAs for destruction
245
How many base pairs are LncRNAs?
At least 200 base Pairs Long
246
What are some of the functions of LncRNAs?
Some have been found to regulate gene expression
Xist binds one X chromosome in females and silences that specific chromosome (Barr body) by recruiting chromatin remodeling proteins
Various found to be produced from “wrong” DNA strand of target gene, generating antisense strand complementary to target
Inhibits translation and/or contributes to RNAi-mediated destruction of target
247
248
Describe this image:
DNA Space-Filling Model
249
Describe this image:
The Cell Cycle
250
Describe this image:
An Electron micrograph of Nucleosomes (Beads on a string)
251
Detail A-F of this image:
A: DNA Double Helix
B: Beads on a string form of Chromatin
C: Chromatin Fiber packed into Nucleosomes
D: Chromatin fiber folded into Loops
E: Entire Mitotic Chromosome
F: Each DNA Molecule has been packaged into a mitotic chromosome
252
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A linker histone helps to pull the nucleosomes together and pack them into a more compact chromatin fiber
253
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Chromatin-Remodeling Complexes
Using ATP to change the position along the histone cores
254
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The variation of chromatin structure along an interphase chromosome
255
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256
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DNA Replication
257
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Semiconservative DNA Replication
258
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DNA Double Helix is opened at the replication Origin
259
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DNA synthesis at the Y-shaped Replication Fork
260
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Multiple Replication forks along the DNA
261
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DNA Polymerase adds a deoxyribonucleotide to the 3' end of the growing DNA Chain.
262
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At each replication fork, the lagging strand is synthesized in pieces
263
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DNA Polymerase proofreading
264
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Okazaki fragments are synthesized and ligated to form a continuous strand.
265
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The replication machine
266
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DNA Topoisomerase relieves the tension that builds up in front of the replication fork (preventing double-stranded breaks)
267
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DNA End replication repair
268
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DNA telomeres and telomerase adjusting end-replication problem
269
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DNA Damage in the form of Depurinaton and Deamination
270
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Deamination leads to mutations
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