Exam 2 pt3 Flashcards
ncRNA carry out diverse functions because they can
bind to different type of molecules, like:
* DNA
* RNA
* proteins
scaffold
when ncRNA binds to a group of proteins
guide
ncRNA binds to a protein and guides it somewhere
ncRNA functions
- scaffold
- guide
- alter protein
- blocker
- ribozyme
- decoy
RNA in RNA world carried three key functions
- info storage
- self replication
- catalytic activity
information storage, how RNA did, why evolve, how evolve
- RNA store infor in base sequence
- DNA storage more stable though
- with DNA storage RNA can multitask
- RNA made DNA with reverse transcription
Metabolism: how RNA did, why evolve, how evolve
- RNA did these
- proteins give benefit of more catalytic activity
- protein have many functions
- protein more advantageous
HOTAIR
ncRNA that alters chromatin structure
HOTAIR located on and transcribed by
HoxC genes, transcribed by the antisense strand of HoxC genes
HOTAIR acts as a
scaffold that guides two histone modifying complexes to genes
HOTAIR mechanism
- PRC2 binds HOTAIR at 5’ end
- LSD1 complex binds 3’ end
- HOTAIR binds GA rich region in target gene
- PRC and LSD1 methylate gene
- inhibit two genes
_ is better at silencing that _ RNA
dsRNA than antisense RNA
RNAi
dsRNA causes silencing of mRNA
RNAi mediated by
miRNAs and siRNAs
miRNA transcribed from _ genes while siRNA from _ genes
endogenous, exogenous
mechanism of RNAi
2
Pri miRNA → pre miRNA → out of nucleus →
OR
pre siRNA enters cell
THEN
→ cut by dicer → form RIS complex → sense strand degraded → bind to target mRNA
- if miRNA, partial match, so translation is silenced
- if siRNA, perfect match so RNA is degraded
chap 17 page 30
RISC composed of
it is a dsRNA produced from either pre-miRNA or pre-siRNA
RNAi functions and benefits
- gene regulation with production of miRNA
- defense against virus
- transcription inhibition
snoRNAs modify _ by _
rRNAs by methylation of ribose on 2’ OH and uracil to conversion
snoRNA two types and what each does
- C/D box catlayze methylation of ribose
- H/ACA box catlyzes concertion of uracil to psedouracil
adaptation phase of CRISPR
- spacer squisition
- Cas1 & 2 cleave bacteriophage DNA
- peice is inserted into Crispr gene
- spacer passed on to daughter cells
expression phase of crispr
- Crispr, tracr and Cas9 genes are expressed
- trancrRNA is complementary to parts of pre-crRNA so it cleaves and makes crRNA
- crRNA-tracrRNA complex binds to Cas9
interference phase of cripsr
- crRNA spacer complementary to bacteriophage DNA
- crRNA acts as a guide that causes trancrRNA-Cas9 complex to bind
- Cas9 protein endocuclease that makes ds break
- bacteriophage proliferation yeeted
PIWI interacting RNAs silence _ in two ways:
silence TE in two ways
* prevent transcription
* directly inhibit RNA in cytosol
how do PIWI RNAs silence transcription
pre-prRNA transcribed → cleaved to make piRNA → makes PRITS complex→ PRITS bind during transcription → modify TE gene → heterochromatin formation →silence transcription
how do PIWI RNA directly inhibit
pre-prRNA transcribed → cleaved to make piRNA → makes PRISC complex→ PRISC binds to TE RNA → perfect match → dsRNA degraded
A small effector molecule that enhances transcription binds to a regulatory protein and causes it to not bind to the DNA. The regulatory protein
is a repressor
During diauxic growth involving glucose and lactose, bacterial cells
use up glucose first, then they metabolize lactose.
For a riboswitch that controls transcription, what is the effect of a regulatory molecule such as TPP?
It binds to an RNA molecule and causes a change in its conformation.
What is the role of mediator with regard to eukaryotic gene regulation?
Mediator controls the switch to the elongation phase of transcription.
The following list describes events that are required for transcription of a eukaryotic gene. Put them in the correct order.
- Chromatin remodeling and histone modification
- Binding of activators
- Elongation
- Formation of the pre-initiation complex
2, 1, 4, 3
The main role of the polycomb group complexes is to
cause gene repression in specific cell types.
The Avy allele of the Agouti gene involves the insertion of a transposable element upstream from the normal Agouti promoter. Let’s suppose that pregnant female mice are fed a diet that contains chemicals that increase DNA methylation. With regard to offspring carrying the Avy allele, this diet would
cause their fur to be less yellow (more dark brown) because the Agouti gene would tend to be under expressed.
Which genes of the CRISPR-Cas system are not needed for the expression and interference phases?
Cas1, Cas2
A mutation in the operator site that prevents the lac repressor from binding would mean, would this be in merozygote
lac is always expressed
cis effect, yes
would this be in merozygote, what would happen if there was a mutation so allolactose cannot bind
repressor stays bound
trans effect, other repressors will bind allolactose and overcome mutation
_ motif promotes formation of dimer formation
zipper motif
