Flashcards in Genes and Chromosomes (Part 1) Deck (16):
Describe the common structure of all nucleotides.
A phosphate group linked by a phosphoester bond to a pentose (a 5 carbon sugar molecule) that in turn is linked to an organic base.
What type of bond links the pentose sugar to the phosphate ester of a nucleotide?
The phosphate is esterified to the C5’ of the pentose sugar by means of an ester bond (phosphoester bond)
What type of bond links the heterocyclic base to the pentose sugar?
The N-glycosidic bond attaches the base to the 1’ position of the sugar in both DNA & RNA
Which nitrogenous bases are purines?
adenine and guanine
Which nitrogenous bases are pyrimidines?
-and uracil (RNA)
What forms phosphodiester bonds?
- DNA/RNA Polymerase
- DNA Ligase (Condensation rxn)
In relation to nucleotides, where do phosphodiester bond forms?
The 5’ CH2 group of one residue becomes linked to the 3’ OH group of the next.
Which bases interact with one another in the interior of the double helix of DNA, and how many H bonds do they form?
The bases on opposite strands of the DNA are held together by?
If a sample of DNA contains 35% adenine, what is % of the other nucleotides?
A = 35%; T = 35% C = 15%; G = 15%
What are the differences between bacterial and human mRNA?
Bacterial: used and degraded within minutes.
Human: used and degraded within hours to days
What are the post-transcriptional modifications of mRNA in Eukaryotes?
1) Transcription by RNA Polymerase II
2) Addition of 5' cap structure
3) Addition of 3' poly-A tail
What is the first step in the capping of eukaryotic 5’ mRNA by addition of a 7-methyl- guanosine (7-Me G)?
A phosphatase removes one phosphate group from the 5’ end of the nascent RNA.
In regards to the formation of the 7-Me-G' mRNA cap, what happens after a phosphatase removes one phosphate group from the 5’ end of the nascent RNA.
Guanylyl transferase: adds a GMP in a reverse linkage (5’ to 5’ instead of 5’ to 3’).
In regards to the capping of mRNA, what happens after Guanylyl transferase adds a GMP in a reverse linkage (5’ to 5’ instead of 5’ to 3’)?
Guanine-7-methyl transferase: adds a methyl group to the 7 position of the terminal guanine.