Bio 112 - 2.7 - Types of RNA and the Fate of the Primary Transcript

why are not all primary transcripts processed into mRNA?

because not all genes code for proteins

how come in prokaryotes translation can happen while transcription is still occurring?

because prokaryotes have no nuclear envelope separating transcription and translation

why is the 5' cap essential for translation?

because the ribosome recognizes an mRNA by its 5' cap

what are the names of the two segments which RNA is spliced into?

introns and exons

polycistronic mRNA?

mRNA that can code for multiple proteins, that are most often found in prokaryote mRNA only

mRNA? what does it do?

messenger RNA. it is the RNA molecule that combines with the ribosome to direct protein synthesis. carries genetic info from DNA to ribosome

5' cap?

modified nucleotide which is attached to the end of the primary transcript, and is connected to the two 5' carbons of both ribose sugars via a triphosphate bond

what is needed for alternative splicing to occur?

multiple introns in genes

introns?

pieces of the RNA which are removed. non-coding genes

alternative splicing?

process in which primary transcripts from the same gene can be spliced in different ways to yield different mRNA's and therefore different protein products

what are the other types of noncoding RNA?

ribosomal RNA, transfer RNA, small nuclear RN, micro RNA and small interfering RNA

rRNA?

ribosomal RNA. found in all ribosomes that aid in translation

snRNA?

small nuclear RNA. found in eukaryotes and involved in splicing, polyadenylation, and other processes in the nucleus

microRNA?

small regulatory RNA molecules that inhibit translation

primary transcript? what does it contain?

the RNA transcript that comes off the template DNA strand. contains genetic information of the gene that was transcribed which will direct the formation of the protein corresponding to that gene

polyadenylation?

the addition of a string of about 250 consecutive A-bearing ribonucleotides to the 3' end forming a poly(A) tail, which helps stabilize the RNA transcript and protect it from being broken down before it is translated

how does RNA splicing work?

the ends of the intron undergo base pairing with RNA molecules in the spliceosome, and are brought close to each other. They form a loop with one end attaching to the end and then the axons on either side come together so the introns are released

lariat?

the name of the loop formed when the intron ends attach together

in prokaryotes, what is equivalent to the mRNA?

the primary transcript

RNA splicing?

the removal of introns which is catalyzed by a spliceosome

what are the most abundant types of RNA?

80% rRNA and 10% tRNA

small interfering RNA?

RNA which cause destruction of an RNA transcript

spliceosome?

complex of RNA and protein responsible for catalyzing RNA splicing

exons?

genes which ARE coded for

RNA processing?

eukaryotic process in which the primary transcript is converted into mRNA readable by the ribosome

in eukaryotes, where does transcription take place? translation?

transcription takes place in the nucleus and translation in the cytoplasm

tRNA?

transfer RNA. carries individual amino acids for use in translation