Chapter 10 Flashcards
3 Major Classes of RNA
mRNA, rRNA, tRNA
What parts of DNA make up a transcription unit?
Promoter, Transcription start site, Terminator
What are the three basic stages of transcription? Describe what happens at each stage
Initiation - forms open complex, Elongation - synthesis of RNA, Termination - RNA polymerase reaches termination sequence
Why do most RNA molecules have 3 phosphate groups at the 5’ end but not DNA molecules?
During initiation DNA nucleoside triphosphate must be attached to a 3 OH of an RNA molecule by DNA polymerase, removing the last 2 phosphates. RNA polymerase does not require the 3 OH to initiate synthesis.
What are the three primary regions of mRNA sequences in bacterial cells?
5’ untranslated region, protein-coding region, 3’ untranslated region
What is the function of the Shine-Dalgarno sequence?
It enable initiation of protein synthesis by aligning the ribosome with the start codon.
What is the 5’ cap?
Its purpose is to protect the mRNA from being broken down in its journey out of the nucleus to the ribosomes and is used for attachment to these ribosomes.
What is the function of the spliceosome?
It is responsible for the removal of noncoding segments from pre-messenger RNAs.
What is alternative splicing? How does it lead to the production of multiple proteins from a single gene?
Alternative splicing is when a single pre-mRNA can be spliced in more than one way to produce different types of mRNA. The same pre-mRNA can be spliced in more than one way to yield different mRNAs that are translated into different amino acid sequences and thus different proteins.
Briefly describe the structure of tRNAs.
tRNA takes on its characteristic structure through complementary base pairing within its RNA sequence. This means that one region of the tRNA is complementary to another region of the tRNA, interacting via hydrogen bonding.
What is the origin of small interfering RNAs and microRNAs? What do these RNA molecules do in the cell?
The siRNAs originate from the cleavage of mRNAs, RNA transposons, and RNA viruses by the enzyme Dicer. The miRNAs arise from the cleavage of individual RNA molecules that are distinct form other genes. Both siRNAs and microRNAs silence gene expression through a process called RNA interference.
