LECTURE 22 Flashcards
why RNA is different from DNA
-RNA has a ribose sugar (it bears a hydroxyl (–OH) group on its 2’ carbon)
-RNA contains the base uracil in place of thymine
RNA also has tertiary structure (example:
tRNAs-see ahead).
-RNAs may interact as functional units
(quaternary structure)(example: in the
ribosome).
- RNA is more reactive than DNA
why RNA is less stable than DNA
Partly is a carry on from evolution – RNA evolved first
* Partly because RNA can form many tertiary structures allowing it to
have different conformations for different functions, whereas DNA is
generally only double stranded
* Partly because an easily temporary and degraded molecule offers a
way of controlling its level (for example shutting off expression).
RNA has an extra -OH group, which make it more reactive.
how is the coding region of the gene in prokaryotes? are the transcription and translation happen at the same time in prokaryotes
In prokaryotes, the coding region of a gene is often a single, continuous unit
-transcription and translation and mRNA degradation occur at the same time (they are coupled)
what are exons and introns?
In eukaryotes, the coding region of a gene is often interrupted:
exons are protein coding segments, introns are intervening (non-coding) segments
in eukaryotes where do the transcription and translation happen
In eukaryotes, transcription and translation are not coupled-rather, RNA transcripts are made and processed in the nucleus and then
must be transported to the cytoplasm for translation
what is mRNA?
Messenger RNAs (mRNAs)—intermediates that carry genetic information from DNA to theribosomes.
what is tRNA
Transfer RNAs (tRNAs)—adaptors between amino acids and the codons in mRNA
What is rRNA?
Ribosomal RNAs (rRNAs)—structural and catalytic components of ribosomes
what is snRNA
Small nuclear RNAs (snRNAs and snoRNAs)—
spliceosomes and rRNA, tRNA modification,
respectively.
What is mi, si and crispr RNA?
Micro RNAs (miRNAs, siRNA and Crispr RNA)—short RNAs that block expression of complementary mRNAs
What is long noncoding RNA
Long noncoding RNAs- long RNAs that regulate gene transcription
are all RNAs encode protein
Many RNAs do not encode protein. We will discuss these RNAs and their function in the last lecture on transcription.
what is the direction of the RNA synthesis and what is the direction of the tempelate in transcription
RNA is synthesized in the 5’ to 3’ direction using the 3’to 5’ DNA template strand. Thus, RNA synthesis is complementary and
anti-parallel to the DNA template strand.
what is the sense strand
Non-template or coding strand also called the sense strand
what is the antisense strand
Template or noncoding
strand also called the
antisense strand
