biol 3250 - chapter 17 and 18

is most cell types, ncRNAS are more…

abundant than mRNAs

ncRNAS can bind to ?

DNA, mRNA, proteins, small molecules and other ncRNAs

ribozyme

RNA molecules with catalytic function

blocker

a ncRNA physically prevents or blocks a cellular process from happening

decoy

a ncRNA recognizes another ncRNA and sequesters it

ncRNAS performs a diverse set of functions and can act as ?

ribozymes

blockers

decoys

precursor to living cells

protobiont

RNA ribozyme catalyzes the peptide bond during protein synthesis, scientists proposed ?

RNA world

scientists argue that proteins were always available, were part of the ?

evolutionary process and question the RNA world theory

hox transcript antisense intergenic RNA

HOTAIR ncRNA - alters chromatin structure and represses transcription

dsRNA that contains both antisense RNA and sense RNA are ?

more effective at inhibiting mRNA translation ; than antisense RNA and sense RNA - ALONE

microRNAs (miRNAs)

transcribed from endogenous eukaryotic genes

• regulate gene expression

• a single type of miRNA inhibits translation of many mRNAs though partial complementary

  • 60% of human genes may be regulated by miRNAs

small interfering RNAs (siRNAs)

ncRNAs that usually originate from exogenous sources, usually viruses

• not made by cells

DS pre-miRNA from cell or DS pre-siRNA from a viral infection associates with proteins to form ?

RNA-inducing silencing complex (RISC) that silences mRNA

small nucleolar RNAs (snoRNAs) direct ?

covalent modifications to ribosomal RNAs

the cripsr gene contains a series of repeats that are interspersed with short unique sequences called ?

spacers

• derived from invading bacteriophage

CRISPR

clustered, regularly, interspaced, short, palindromic repeats

• cas bacterial defense system against bacteriophages

the crispr gene produces a ncRNA called ?

pre-crRNA

• contains the unique spacer sequences from bacteriophages and the repeat sequences

a region of the tracrRNA is complementary to the ?

repeat sequences of the pre-crRNA

ncRNAa called PIWI - interacting RNAs (piRNAs) can ?

silence transposable elements

virus

they do not contain the required metabolic pathways to make their own energy and replicate independently of a host

all viruses have a nucleic acid genome (DNA or RNA) surrounded by a ?

protein capsid

two categories of viruses

1. some viruses are strictly lytic and lyse/kill their host

   1. some viruses are temperate or latent and have lysogenic life cycles where they integrate into the host chromosome and remain dormant - until they go lytic, replicate, lyse the host

prophage

bacterial virus that has integrated into the chromosome

provirus

for a eukaryotic virus that has integrated into the host chromosome

the key to the decision between lysogeny and lysis lies in the ?

interaction between the cl and cro genes

the first genes made when λ infects a host are ?

N and cro

N allows ?

cII and cIII to be made

• which try to turn on cI

cII

is an activator but is unstable and readily degraded by cellular proteases

cIII

stabilizes cII against degradation by cellular proteases

cro can promote ?

lysis

• while cI, cII and cIII promote lysogeny

cro can prevent the expression of ?

cI

• while cI can prevent the expression of cro

cI activates its own expression, while the expression of ?

cro requires no activation

N and Q are ?

antiterminators that extend mRNA transcripts and control the timing of λ lysis

cI (λ repressor protein)

represses lysis by turning off cro

cro (control of repressor’s operator)

represses lysogeny by turning off cI

N (aNtiterminator)

antiterminates and allows the extension of major transcripts

cII with some help from cIII, which stabilizes cII and prevents it from being degraded by cellular proteases- is trying to make ?

cI via Pre

cro is trying yo shut off cI that is being made via ?

Pre

• cro can also shut off cI via Prm

the cII protein is easily degraded by a cellular protease produced by ?

e.coli

environmental conditions that are favorable for growth promote the ?

lytic cycle

environmental conditions that are unfavorable for growth promote the ?

lysogenic cycle

many of the HIV proteins are contained within the virus, including ?

reverse transcriptase

integrase

• needed during early steps in the viral reproductive cycle

HIV reverse transcriptase can replicate ?

DNA from both RNA and DNA

three types of HIV RNAs are made

1. fully spliced HIV RNA

2. incompletely spliced HIV RNA

3. unspliced HIV RNA

fully spliced HIV RNA

early in this process, HIV RNA is fully spliced

• RNA exits the nucleus and is used to translate Nef, Tat and Rev proteins

• the Nef protein inhibits host cellular defense proteins

• Tat and Ref proteins enter the nucleus

incompletely spliced HIV RNA

incompletely spliced RNA exits the nucleus with the help of the Rev protein

• the RNA is translated into Vif, Env, Vpu and Vpr proteins

• Rev protein is required for this process because normally incompletely spliced RNA that contains introns cannot exit the nucleus

unspliced HIV RNA

unspliced HIV RNA also exits the nucleus with help of the Rev protein

• unspliced HIV RNA is translated to make Gag polyprotein and Gag-pol polyprotein

• the unspliced HIV RNA is also incorporated into new virus particles

the NEF protein inhibits ?

host cellular defense proteins

the REV protein allows ?

unspliced or incompletely spliced HIV RNAs to exit the nucleus

the TAT protein is a ?

transcriptional activator that enables the transcription of HIV genes

as the capsulated HIV buds from the host cell it picks up host proteins and becomes ?

enveloped

• thus the HIV capsid contains both viral and host proteins