From DNA to RNA Flashcards
week 2
DNA does not direct protein synthesis directly, instead it copies into RNA:
transcription
RNA copies of DNA segments direct synthesis of protein:
translation
what is the Central Dogma aka fundamental process?
DNA to RNA to protein
what is rna?
linear polymer made of 4 diff nucleotides
on uracil, the absence of its methyl group has no effect on base pairing but can affect what?
DNA repair
what are mRNAs?
messenger RNAs, code for proteins
rRNAs?
ribosomal RNAs, form the basic structure of the ribosome; catalyze protein synthesis
tRNAs?
transfer RNAs, central to protein synthesis as the adaptors bw mRNA and amino acids
telomerase RNA?
serves as the template for telomerase enzyme that extends the ends of chromosomes
snRNAs?
small nuclear RNAs, function in a variety of nuclear processes, including splicing of pre-mRNAs
snoRNAs?
small nuclear RNAs, help to process and chemically modify rRNAs
IncRNAs
long encoding RNAs, not all of which have a function; some serve as scaffolds and regulate diverse cell processes, including X-chromosome inactivation
miRNAs?
microRNAs, regulate gene expression by blocking translation of specific mRNAs and causing their degradation
siRNAs
small interfering RNAs, turn off gene expression by directing the degradation of selective mRNAs and helping to establish repressive chromatin structures
piRNAs
Piwi-interacting RNAs, bind to piwi proteins and protect the germ line from transposable elements
what is a transcription unit?
a transcribed segment of DNA; info in just one gene for just one RNA molecule or single protein
what 3 RNA polymerases are involved in transcription?
RNA pol I,II, III
what are general transcription factors?
proteins that initiate transcription
sequence of DNA nucleotides that signal the starting point for RNA synthesis
promoter
how are introns removed?
splicing
how are exons joined?
with help of small nuclear RNAs (snRNAs)
how much RNA in eukaryotic cells is rRNA?
80%
why are general transcription factors used?
RNA polymerases require them to initiate transcription; DNA packaging into nucleosomes is a problem
how does a supercoil form?
for every 10 nucleotides open, a supercoil forms
what causes a dna supercoil to form?
elongation, bc of the need to unwind the helix
what helps remove the tension in transcription to help prevent coiling?
DNA topoisomerase
where do transcriptional activators bind?
“enhancer” sequences
what is required so that activators can communicate with transcription complex?
mediator
when are chromatin and remodeling proteins/enzymes recruited?
with mediator
what determines when RNA pol will dissociate from the helix?
elongation factors
proteins that decrease the likelihood that RNA pol will dissociate before it reaches end of a gene
elongation factors
what two impediments does transcription elongation face?
nucleosomes and DNA supercoiling
in what direction is transcription?
5’ to 3’ (like replication)
how many strands are used as template in transcription?
one
RNA pol II is also known as what?
rna synthesis and processing machine
only exons are transcribed into RNA. T or F?
false, both introns and exons are transcribed
how are introns removed?
by splicing
Exons are joined with help of what? (these recognize splice sequence)
small nuclear RNAs (snRNAs)
what do snRNPs form?
form the core of the “spliceosome”
splicing is flexible if alternative proteins need to be made / mutations present in the gene
alternative splicing
what are the 3 ways alternative splicing occurs in disease?
exon skipping, activating cryptic splice site, creates new splice site
what happens to mature mRNAs?
transported from nucleus to cytoplasm
most abundant type of RNA (80%)
rRNA
what transcribes rRNAs?
rna pol I
