MCP 2 Flashcards
(284 cards)
1
Q
What are the three components of a DNA nucleotide?
A
A phosphate group, a deoxyribose sugar, and a nitrogenous base.
2
Q
Which DNA bases are purines and how many rings do they have?
A
Adenine and guanine; each has a double-ring structure.
3
Q
Which DNA bases are pyrimidines and how many rings do they have?
A
Cytosine and thymine; each has a single-ring structure.
4
Q
What kind of bond links adjacent nucleotides in DNA?
A
5’→3’ phosphodiester bond.
5
Q
Why are DNA strands described as antiparallel?
A
One strand runs 5’→3’ while the complementary strand runs 3’→5’.
6
Q
What is the diameter of the B-form DNA double helix?
A
About 2 nm.
7
Q
Which groove of DNA provides wider access for DNA-binding proteins?
A
The major groove.
8
Q
State the base-pairing rules in DNA.
A
A pairs with T, and G pairs with C.
9
Q
How many base pairs wrap around a histone octamer?
A
Approximately 146 bp.
10
Q
Name the four core histones in a nucleosome.
A
H2A, H2B, H3, and H4.
11
Q
How many turns of DNA wrap around each histone core?
A
About 1.65 turns.
12
Q
What is typical linker DNA length between nucleosomes?
A
Roughly 20–80 bp (about 20 bp on average).
13
Q
What histone promotes formation of the 30 nm fiber?
A
Histone H1.
14
Q
Contrast euchromatin and heterochromatin.
A
Euchromatin is less condensed and transcriptionally active; heterochromatin is highly compacted and usually silent.
15
Q
During which mitotic stage are chromosomes most condensed?
A
Metaphase.
16
Q
What effect does histone acetylation have on chromatin?
A
Neutralizes histone charge, loosens DNA binding, and promotes gene activation.
17
Q
Which enzymes add acetyl groups to histones?
A
Histone acetyltransferases (HATs).
18
Q
Which enzymes remove histone acetyl groups?
A
Histone deacetylases (HDACs).
19
Q
Give an example of an activating histone methyl mark.
A
H3K4me3 at active promoters.
20
Q
Give an example of a repressive histone methyl mark.
A
H3K27me3 at silent genes.
21
Q
What is meant by the ‘histone code’?
A
Combinations of histone modifications act as a code that dictates chromatin state and gene expression.
22
Q
Where does DNA methylation typically occur in mammals?
A
At cytosines in CpG dinucleotides.
23
Q
What enzyme family writes DNA methylation marks?
A
DNA methyltransferases (DNMTs).
24
Q
What is a CpG island?
A
A region rich in CpG sites, often found in gene promoters.
25
How does promoter methylation usually affect transcription?
It silences gene expression.
26
Which enzymes initiate active demethylation of 5-methylcytosine?
TET family dioxygenases.
27
Differentiate maintenance and de novo DNA methylation.
Maintenance copies existing patterns after replication; de novo establishes new patterns.
28
What is a pioneer transcription factor?
A factor able to bind partially closed chromatin and initiate its opening.
29
List the core elements of a typical eukaryotic promoter.
TATA box, transcription start site, and adjacent regulatory motifs.
30
How do enhancers regulate transcription?
They bind activator proteins and loop to promoters to increase transcription.
31
What sequence marks the 5' splice site of an intron?
GU in the RNA (GT in the DNA sense strand).
32
What sequence marks the 3' splice site of an intron?
AG.
33
What complexes excise introns from pre-mRNA?
The spliceosome (snRNAs plus proteins).
34
Define alternative splicing.
Joining exons in different combinations to create multiple mRNA isoforms from one gene.
35
What modification is added to the 5' end of mRNA?
A 7-methylguanosine cap.
36
What is the function of the poly-A tail?
Stabilizes mRNA and aids nuclear export and translation.
37
Which codon starts translation and which amino acid does it encode?
AUG; it encodes methionine.
38
Name the three stop codons.
UAA, UAG, and UGA.
39
Outline the three temperature steps of a PCR cycle.
Denaturation ~95 °C, annealing ~50–60 °C, extension ~72 °C.
40
Why is Taq polymerase used in PCR?
It remains active at high temperatures required for denaturation.
41
What primer length and GC content are generally recommended for PCR?
18–24 nt with ~50–55 % GC.
42
State Wallace’s rule for estimating primer Tm.
Tm ≈ 2 °C × (A+T) + 4 °C × (G+C).
43
What is a GC clamp and why add one?
One or two G/C bases at the primer 3' end to improve binding stability.
44
Why design cDNA primers across exon–exon junctions?
To avoid amplifying contaminating genomic DNA containing introns.
45
Define epigenetics.
Heritable changes in gene expression not caused by DNA sequence alterations.
46
Give an example of intergenerational epigenetic effect in humans.
Dutch Hunger Winter offspring showing altered methylation and health outcomes.
47
What is genomic imprinting?
Parent-specific mono-allelic expression of certain genes via epigenetic marks.
48
Which growth factor gene is paternally expressed and promotes fetal growth?
IGF2.
49
Loss of paternal 15q11–13 causes which syndrome?
Prader-Willi syndrome.
50
Loss of maternal UBE3A leads to which disorder?
Angelman syndrome.
51
What RNA initiates X-chromosome inactivation?
Xist lncRNA.
52
What is a Barr body?
The condensed, inactive X chromosome in female nuclei.
53
Why are female mammals genetic mosaics for X-linked genes?
Each cell randomly inactivates either the maternal or paternal X during early development.
54
Define long non-coding RNA (lncRNA).
Non-protein-coding RNA >200 nt with regulatory roles.
55
Name two lncRNAs involved in chromatin silencing.
Xist and HOTAIR.
56
Outline miRNA biogenesis steps.
Pri-miRNA → Drosha → pre-miRNA → export → Dicer → mature miRNA loaded into RISC.
57
How do miRNAs suppress gene expression?
They guide RISC to target mRNAs, causing degradation or translational repression.
58
What is an oncomiR?
A microRNA whose overexpression promotes cancer by silencing tumor-suppressor genes.
59
State two epigenetic hallmarks of many cancers.
Global DNA hypomethylation and promoter CpG island hypermethylation.
60
Name a drug class that reactivates silenced tumor suppressor genes.
DNA methyltransferase inhibitors (e.g., azacitidine).
61
What are the two primary skin layers?
Epidermis and dermis.
62
Which cells dominate the epidermis?
Keratinocytes.
63
How long is the typical turnover time of human epidermis?
About four weeks.
64
What protein gives skin tensile strength?
Type I collagen in the dermis.
65
What are dermal papillae?
Finger-like projections of the dermis that interlock with epidermal ridges.
66
What skin layer contains hair follicles and glands?
The dermis.
67
Define solar elastosis.
Accumulation of abnormal elastin in photoaged dermis.
68
Which UV type penetrates glass and drives photoaging?
UVA (320–400 nm).
69
Which UV type is the main cause of sunburn?
UVB (290–320 nm).
70
How do advanced glycation end-products (AGEs) affect skin?
Cross-link collagen, decreasing elasticity and promoting wrinkles.
71
What is the senescence-associated secretory phenotype (SASP)?
Inflammatory cytokines and proteases secreted by senescent cells.
72
Which neurotransmitter released by stress can deplete hair-follicle melanocyte stem cells?
Noradrenaline.
73
What does Horvath’s epigenetic clock measure?
Biological age based on DNA methylation at 353 CpG sites.
74
Which gene’s promoter methylation is a strong age marker?
ELOVL2.
75
What happens to DNAm age when cells are reprogrammed to iPSCs (induce pluripotent stem cells)?
It resets to near zero.
76
Define nucleosome.
DNA wrapped around a histone octamer forming the basic chromatin unit.
77
Which histone mark signals DNA damage response by phosphorylation?
H2AX Ser139 (γ-H2AX).
78
How does DNA methylation impede transcription factor binding?
Methyl groups protrude into the major groove, blocking protein access or recruiting repressors.
79
What is maintenance methyltransferase DNMT1’s role?
Copies methylation pattern to daughter strand after DNA replication.
80
State the GT-AG rule in splicing.
Introns start with GU and end with AG in RNA (GT…AG in DNA).
81
What is a polyadenylation signal in pre-mRNA?
AAUAAA sequence that signals cleavage and poly-A tail addition.
82
Why are most disease-causing mutations found in exons?
Because exons encode protein; changes directly alter protein function.
83
What is the Hayflick limit?
Finite number of divisions normal human cells undergo before senescence.
84
Give one guideline to avoid primer-dimer formation.
Ensure primers are not complementary at their 3' ends.
85
What does DNMT3A/B do?
Carry out de novo DNA methylation during development.
86
What is a CpG desert?
Genome region with low CpG density.
87
How do HDAC inhibitors act as anticancer agents?
Keep chromatin open, potentially reactivating silenced tumor-suppressor genes.
88
What structural protein in the stratum corneum provides barrier function?
Keratin.
89
What are matrix metalloproteinases (MMPs)?
Enzymes that degrade extracellular matrix proteins like collagen.
90
Name one senolytic strategy.
Drugs that selectively induce apoptosis in senescent cells.
91
Define phototype.
Classification of skin’s reaction to UV exposure and baseline pigmentation.
92
Why does smoking accelerate facial wrinkling?
Free radicals damage collagen and elastin, and vasoconstriction reduces nutrient supply.
93
What is a DNA primer’s 3' hydroxyl group required for?
DNA polymerase extension.
94
What purpose does the 5' cap serve for mRNA export?
It is recognized by nuclear export receptors.
95
What is the function of fibroblasts in wound healing?
Produce collagen and extracellular matrix to close and remodel the wound.
96
Explain the parental conflict theory of imprinting.
Paternal genes favor fetal growth; maternal genes conserve maternal resources by limiting growth.
97
Which enzyme complex adds trimethyl marks to H3K27?
Polycomb Repressive Complex 2 (PRC2).
98
Why are CpG islands usually unmethylated in housekeeping genes?
To keep promoters open for constant transcription.
99
What type of RNA is Airn and what does it do?
A lncRNA that silences paternal genes in an imprinted cluster.
100
What chromatin state is associated with H3K9me3?
Constitutive heterochromatin.
101
What does Dicer enzyme produce?
~22-nt miRNA duplexes from pre-miRNA hairpins.
102
Name the heat-stable polymerase first used in PCR.
Taq polymerase.
103
How does UV light create mutagenic lesions in DNA?
Forms thymine dimers that distort the helix.
104
Which dermal layer contains dense collagen bundles?
Reticular dermis.
105
State one clinical use of DNMT inhibitors.
Treatment of myelodysplastic syndrome or certain leukemias.
106
What is the main structural difference between RNA and DNA sugars?
RNA has a 2' hydroxyl on ribose; DNA lacks it (deoxyribose).
107
Which nucleic acid base is found in RNA but not DNA?
Uracil.
108
What is the average human nucleus diameter?
About 6 µm.
109
How many meters of DNA are packed into a nucleus of one human cell?
Roughly 2 m.
110
Which histone variant is incorporated at sites of DNA damage?
H2A.X.
111
What is a GC-rich primer prone to forming at high concentrations?
Secondary structures such as hairpins.
112
How does a spliceosome recognize splice sites?
By conserved GU and AG dinucleotides and branch-point sequence.
113
What skin appendage secretes sebum?
Sebaceous gland.
114
Name one antioxidant vitamin that helps neutralize UV-induced free radicals.
Vitamin C or vitamin E.
115
Why can promoter mutations in a TATA box reduce gene transcription?
They impair RNA polymerase II positioning at the start site.
116
What is an epigenome?
The complete set of epigenetic modifications across the genome of a cell.
117
How does caloric restriction impact epigenetic aging?
Generally slows the progression of epigenetic clock measures.
118
Which fibroblast subpopulation resides in the upper dermis?
Papillary fibroblasts.
119
Give one function of 5' UTR regions.
Regulate translation initiation efficiency.
120
State the typical size range of a standard PCR product.
About 100–1000 bp.
121
'What is a nucleosome?'
'An octamer of histones (2×H2A
122
'Which enzyme cuts linker DNA in chromatin studies?'
'Micrococcal nuclease (MNase)'
123
'What effect does histone acetylation have on chromatin?'
'Relaxes chromatin by neutralizing positive charges on histone tails'
124
'Which enzymes add acetyl groups to histones?'
'Histone acetyltransferases (HATs)'
125
'Which enzymes remove acetyl groups from histones?'
'Histone deacetylases (HDACs)'
126
'How does histone methylation affect gene expression?'
'It can activate or repress depending on which residue is methylated'
127
'Which donor molecule provides methyl groups for histone methylation?'
'S-adenosyl methionine (SAM)'
128
'What percentage of human promoters have CpG islands?'
'~70 %'
129
'On which cytosine position does DNA methylation occur?'
'5-carbon of cytosine in CpG dinucleotides'
130
'Name the enzyme family responsible for DNA methylation.'
'DNA methyltransferases (DNMTs)'
131
'What effect does DNA methylation have on chromatin?'
'Condenses chromatin and impedes transcription'
132
'What is passive DNA demethylation?'
'Loss of 5-methylcytosine during DNA replication without maintenance methylation'
133
'What is active DNA demethylation?'
'TET enzymes convert 5-methylcytosine to 5-hydroxymethylcytosine and further oxidized forms'
134
'What is heterochromatin?'
'Densely packed chromatin
135
'What is euchromatin?'
'Loosely packed chromatin
136
'Define promoter.'
'DNA regulatory region where transcription machinery assembles to initiate transcription'
137
'What is the consensus sequence of the TATA box?'
'TATA(A/T)A(A/T)'
138
'Which protein binds the TATA box to initiate transcription?'
'TATA-binding protein (TBP)'
139
'In which direction does RNA polymerase synthesize RNA?'
'5′ to 3′'
140
'What are UTRs?'
'Untranslated regions of mRNA that flank the coding sequence'
141
'What are the three steps of PCR?'
'Denaturation
142
'At what temperature does denaturation occur in PCR?'
'~94 °C'
143
'At what temperature do primers anneal in PCR?'
'~50–60 °C'
144
'At what temperature does extension occur in PCR?'
'~72 °C'
145
'What is the optimal primer length for PCR?'
'18–24 bp'
146
'Why shouldn’t PCR primers be self-complementary?'
'To avoid primer dimer formation'
147
'How far apart should forward and reverse primers be in PCR?'
'150–400 bp'
148
'What formula estimates primer melting temperature (Tm)?'
'Tm = 2°C×(A+T) + 4°C×(G+C)'
149
'What does bisulfite treatment do to unmethylated cytosine?'
'Converts it to uracil (read as thymine after PCR)'
150
'Which cytosine remains unchanged after bisulfite sequencing?'
'Methylated cytosine'
151
'Name a method to detect methylation-specific PCR products.'
'Use primers specific to converted (unmethylated) or unconverted (methylated) sequences'
152
'What is genomic imprinting?'
'Parent-of-origin–specific gene expression controlled by epigenetic marks'
153
'What are DMRs?'
'Differentially methylated regions controlling imprinting'
154
'What is Prader-Willi syndrome caused by?'
'Deletion of paternal allele or maternal uniparental disomy at 15q11–q13'
155
'What is Angelman syndrome caused by?'
'Deletion of maternal allele or paternal uniparental disomy at 15q11–q13'
156
'Which lncRNA initiates X-inactivation?'
'XIST'
157
'From which chromosome is XIST expressed?'
'The future inactive X chromosome'
158
'What structure forms when an X chromosome is inactivated?'
'Barr body'
159
'Which complex does XIST recruit to deposit H3K27me3?'
'Polycomb Repressive Complex 2 (PRC2)'
160
'What is the biological purpose of X-inactivation?'
'Dosage compensation between XX females and XY males'
161
'What is mosaicism in X-inactivation?'
'Patchwork of cells with different active X chromosomes'
162
'Give an example of phenotypic mosaicism due to X-inactivation.'
'Calico cat coat color patterns'
163
'What is the X-inactivation center (XIC)?'
'Genomic locus where XIST and its antisense regulator TSIX are transcribed'
164
'What role does TSIX play?'
'Antisense transcript that represses XIST on the active X chromosome'
165
'Define lncRNA.'
'Long non-coding RNA >200 nt involved in gene regulation'
166
'Name one mechanism by which lncRNAs act.'
'Scaffold
167
'How do lncRNAs guide epigenetic modifiers?'
'By base pairing or protein interactions to target loci'
168
'What is a miRNA sponge?'
'An RNA that sequesters microRNAs to prevent them from inhibiting target mRNAs'
169
'What is RISC?'
'RNA-induced silencing complex guided by miRNA to degrade or block mRNA'
170
'What is the seed region of miRNA?'
'A 6–8 nt sequence that base-pairs with target mRNA'
171
'What size are mature miRNAs?'
'~20–24 nt'
172
'Where are rRNA genes transcribed?'
'Nucleolus'
173
'What is the function of the nucleolus?'
'Ribosomal RNA synthesis and ribosome assembly'
174
'Name the two chromatin states.'
'Euchromatin and heterochromatin'
175
'What histone mark is associated with active promoters?'
'H3K4me3'
176
'Which histone mark is associated with transcriptional repression?'
'H3K27me3'
177
'What is a pioneer transcription factor?'
'A TF that can bind condensed chromatin and open it'
178
'Name one effect of environmental factors on epigenetics.'
'Altered histone acetylation or DNA methylation'
179
'What kind of chromatin change does acetylation cause?'
'Permissive chromatin state'
180
'What does histone deacetylase inhibition cause?'
'Increased gene expression via hyperacetylation'
181
'What does DNA hypomethylation of promoters cause?'
'Increased transcription'
182
'What is the primary mechanism for long-term gene silencing?'
'DNA methylation followed by chromatin remodeling'
183
'What is the difference between imprinting and X-inactivation?'
'Imprinting affects specific genes parent-of-origin; X-inactivation silences entire X chromosome'
184
'What is CpG island methylator phenotype (CIMP)?'
'Genome-wide promoter hypermethylation in cancers'
185
'What percent of coding DNA is in exons?'
'~1.5 %'
186
'What percent of the human genome is non-coding RNA?'
'~98.5 %'
187
'What is the role of histone demethylases?'
'Remove methyl groups to alter gene expression'
188
'Name a trisubstituted histone modification.'
'H3K4me3 or H3K27me3'
189
'What role do linker histones (H1) play?'
'Stabilize higher-order chromatin structures'
190
'What is chromatin remodeling?'
'ATP-dependent repositioning of nucleosomes'
191
'Which complexes perform chromatin remodeling?'
'SWI/SNF
192
'What is the function of CpG methyl-binding proteins?'
'Recruit repressors to methylated DNA'
193
'Which RNA polymerase transcribes mRNA?'
'RNA polymerase II'
194
'Which RNA polymerase transcribes rRNA?'
'RNA polymerase I'
195
'Which RNA polymerase transcribes tRNA?'
'RNA polymerase III'
196
'What is alternative splicing?'
'Production of different mRNA isoforms from one gene'
197
'Which intron boundaries define splice sites?'
'5′ GU and 3′ AG'
198
'What is a regulatory element upstream of a gene called?'
'Enhancer or silencer depending on function'
199
'What is the nucleosome repeat length?'
'~200 bp'
200
'What technique maps nucleosome positions?'
'MNase-seq'
201
'What is ChIP-seq used for?'
'Mapping protein–DNA interactions genome-wide'
202
'What is the effect of 5-azacytidine on cells?'
'Inhibits DNMTs and causes DNA hypomethylation'
203
'Which assay measures chromatin accessibility?'
'DNase-seq or ATAC-seq'
204
'What does H3K36me3 mark indicate?'
'Transcribed gene bodies'
205
'What is epigenetic inheritance?'
'Transmission of chromatin states through cell division'
206
'What drives tissue-specific gene expression patterns?'
'Combination of TF binding
207
'What is the function of S-adenosyl homocysteine (SAH) in methylation?'
'By-product that can inhibit methyltransferases'
208
'What is the typical length of lncRNAs?'
'>200 nucleotides'
209
'What is the difference between siRNA and miRNA?'
'siRNA is exogenous and perfectly complementary; miRNA is endogenous with partial complementarity'
210
'What process converts pri-miRNA to pre-miRNA?'
'Drosha cleavage in the nucleus'
211
'What process converts pre-miRNA to mature miRNA?'
'Dicer cleavage in the cytoplasm'
212
'What role does exportin-5 play?'
'Exports pre-miRNA from nucleus to cytoplasm'
213
'What is the role of RISC-loading complex?'
'Loads miRNA onto Argonaute in RISC'
214
'What effect does histone ubiquitination have?'
'Can signal for DNA repair or transcriptional regulation'
215
'What modification marks active enhancers?'
'H3K27ac'
216
'What modification marks poised enhancers?'
'H3K4me1 without H3K27ac'
217
'What is X-chromosome counting?'
'Cellular mechanism to ensure only one X remains active'
218
'What is chromatin fiber?'
'30 nm fiber of nucleosome arrays'
219
'What is the role of CTCF?'
'Insulator protein that demarcates topologically associating domains (TADs)'
220
'What is Hi-C used for?'
'Genome-wide chromatin conformation capture'
221
'What is the function of Cohesin?'
'Maintains sister chromatid cohesion and chromatin loop extrusion'
222
'What are topologically associating domains (TADs)?'
'Self-interacting genomic regions that regulate enhancer–promoter contacts'
223
'What role does ATRX play in chromatin?'
'Chromatin remodeling ATPase involved in heterochromatin maintenance'
224
'What is the histone variant H3.3 associated with?'
'Active transcription and regulatory elements'
225
'What is nucleolar organizer region (NOR)?'
'Chromosomal region containing rRNA gene clusters'
226
'What is replication timing?'
'Temporal order of DNA replication
227
'What are lamina-associated domains (LADs)?'
'Genomic regions tethered to nuclear lamina
228
'What is phase separation in chromatin?'
'Liquid–liquid demixing driving heterochromatin domain formation'
229
'Which enzyme adds ubiquitin to histone H2A?'
'RNF2 (Ring1B) of PRC1 complex'
230
'What is the role of ZFP57?'
'Maintains DNA methylation at imprinting control regions'
231
'What is the function of piRNAs?'
'Protect germline genome by silencing transposable elements'
232
'Which enzyme complex processes piRNA precursors?'
'PIWI-clade proteins and Zucchini nuclease'
233
'What is an R-loop?'
'RNA–DNA hybrid with displaced single-stranded DNA'
234
'How can R-loops affect genome stability?'
'They can cause DNA breaks and replication stress'
235
'What modification marks active gene bodies?'
'H3K36me3'
236
'Which enzyme writes H3K36me3?'
'SETD2 methyltransferase'
237
'What is the role of m6A in mRNA?'
'Regulates mRNA stability and translation efficiency'
238
'Which enzyme deposits m6A marks?'
'METTL3–METTL14 methyltransferase complex'
239
'Which protein reads m6A marks?'
'YTH domain-containing proteins'
240
'Which enzyme removes m6A marks?'
'FTO or ALKBH5 demethylases'
241
'What is a super-enhancer?'
'Cluster of enhancers with high transcription factor occupancy'
242
'How do super-enhancers differ from typical enhancers?'
'They drive high-level expression of cell identity genes'
243
'What are CpG shores?'
'Regions flanking CpG islands up to 2 kb away'
244
'How does DNA hydroxymethylation (5hmC) affect gene expression?'
'Associated with active or poised genes in brain development'
245
'Which enzyme converts 5mC to 5hmC?'
'TET family dioxygenases'
246
'What is a bivalent chromatin domain?'
'Locus marked by both H3K4me3 and H3K27me3 in stem cells'
247
'What does bivalent chromatin poise genes for?'
'Rapid activation or repression during differentiation'
248
'What is the role of cohesin in chromatin looping?'
'Extrudes loops to mediate enhancer–promoter contacts'
249
'What effect does PARP1 have on chromatin?'
'Adds ADP-ribose to histones
250
'What is chromatin immunoprecipitation (ChIP)?'
'Technique to map protein–DNA interactions in vivo'
251
'What is ATAC-seq used for?'
'Mapping open chromatin regions genome-wide'
252
'What is the histone variant macroH2A associated with?'
'X-inactivation and transcriptional repression'
253
'Which histone variant is enriched at centromeres?'
'CENP-A (centromere-specific H3 variant)'
254
'What is the function of the nuclear lamina?'
'Provides structural support and organizes heterochromatin'
255
'What is a LAD (lamina-associated domain)?'
'Genomic region tethered to nuclear lamina
256
'What is a RAID (RNA–DNA interaction domain)?'
'Sites where lncRNAs interact directly with chromatin'
257
'What is the action of activation-induced cytidine deaminase (AID)?'
'Deaminates cytosine to uracil in immunoglobulin loci'
258
'How does AID contribute to antibody diversity?'
'Drives somatic hypermutation and class switch recombination'
259
'What is the Goldilocks zone of DNA methylation?'
'Intermediate promoter methylation that permits regulated expression'
260
'What is the histone acetylation reader domain?'
'Bromodomain'
261
'Which proteins contain bromodomains?'
'BET family proteins (BRD2
262
'What is the histone methylation reader domain?'
'Chromodomain'
263
'Which proteins contain chromodomains?'
'HP1 and Polycomb (CBX) proteins'
264
'What is the action of DNMT1?'
'Maintenance DNA methyltransferase copying methylation patterns during replication'
265
'What is the role of UHRF1?'
'Recruits DNMT1 to hemimethylated DNA'
266
'What is the function of SMCHD1?'
'Epigenetic silencing of the inactive X and autosomal genes'
267
'What is enhancer RNA (eRNA)?'
'Short
268
'How do eRNAs affect transcription?'
'Facilitate enhancer–promoter looping and gene activation'
269
'What are topoisomerases?'
'Enzymes that relieve DNA supercoiling by cutting and re-ligating DNA strands'
270
'Which topoisomerase is targeted by camptothecin?'
'Topoisomerase I'
271
'Which topoisomerase is targeted by etoposide?'
'Topoisomerase II'
272
'What is the histone code hypothesis?'
'Combinatorial histone modifications specify distinct chromatin states'
273
'What is liquid–liquid phase separation in the nucleus?'
'Formation of membraneless compartments like nucleoli and speckles'
274
'What drives phase separation of chromatin?'
'Interactions among intrinsically disordered regions of proteins and RNAs'
275
'What is the role of SAF-A/hnRNP U in the nucleus?'
'Anchors XIST RNA and organizes nuclear matrix'
276
'What does the DEAD box helicase DDX5 do?'
'Unwinds RNA secondary structures in transcription and splicing'
277
'What is the mediator complex?'
'Coactivator linking transcription factors to RNA polymerase II'
278
'What is transcriptional pausing?'
'RNA polymerase II temporarily pauses near the promoter before elongation'
279
'Which factor releases paused polymerase?'
'P-TEFb kinase phosphorylating RNA Pol II and DSIF'
280
'What is the role of NELF?'
'Negative elongation factor that stabilizes paused RNA Pol II'
281
'What is cotranscriptional splicing?'
'Splicing of pre-mRNA occurs concurrently with transcription'
282
'Which complex catalyzes mRNA 5′ capping?'
'Capping enzyme complex associated with RNA Pol II CTD'
283
'What is the function of the 3′ poly(A) tail?'
'Enhances mRNA stability and translation initiation'
284
How many base pairs in a full turn of DNA?
10.5
