Saturday, July 30, 2011

DNA/RNA/etc.





Compare and contrast of DNA & RNA
DNA: Deoxyribonucleic acid that contains 5 carbon sugar deoxyribose . 
RNA: Ribonucleic acid that contains 5 carbon sugar ribose

DNA: Double stranded
RNA: Single stranded

DNA: (A)adenine, (T)thymine, (C)cytosine, (G)guanine
RNA:  Contains all of the above except Thymine, which is replaced by (U)uracil 

Both: Composed of Nucleotides that are linked by chemical bonds between sugar of one nucleotide and the phosphate of the next 

RNA: Has several types, mRNA, tRNA, rRNA
DNA: Can undergo self-replication, RNA cannot










Enzymes involved in DNA replication

Helicase: Unwounds a portion of the DNA Double Helix
RNA Primase: Attaches RNA primers to the replicating strands.
DNA Polymerase delta : Binds to the 5' - 3' strand in order to bring nucleotides and create the daughter leading strand.
DNA Polymerase epsilon : Binds to the 3' - 5' strand in order to create discontinuous segments starting from different RNA primers.
Exonuclease (DNA Polymerase I): Finds and removes the RNA Primers
DNA Ligase: Adds phosphate in the remaining gaps of the phosphate - sugar backbone
Nucleases: Remove wrong nucleotides from the daughter strand.






Transcription in Eukaryotic cell


Transcription is the synthesis of messenger RNA from a DNA Template.
Transcription takes place in the nucleus of  a Eukaryotic cell and produces a pe-mRNA
Molecule. The pre-mRNA molecule is processed to produce a mature mRNA , which exits the nucleus
and is then translated to the cytoplasm. 


Translation is the synthesis of a protein from a messenger RNA template.
In translation, the mRNA that was produced by transcription is decoded by the ribosome
to produce a specific amino acid chain that will later become an active protein.



Transcription in Prokaryotic cell


In a prokaryotic cell Transcription and Translation are coupled, because translation 
begins while the mRNA is still being synthesized.

Transcription in Eukaryotic vs. Prokaryotic cells
 Transcription in Prokaryotic cell occurs throughout the cell;
Transcription in a Eukaryotic cell occurs in the nucleus 
 Transcription in Eukaryotic cells undergoes some modifications (with mRNA)
while transcription in prokaryotic cells do not.
They both have the same finishing product, mRNA



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