10/22 Flashcards
DNAPI 5’-3’ exonuclease activity:
DNAPI 5’-3’ exonuclease activity: used to remove the RNA primer and then it’s 5’-3’ polymerase activity replaces the RNA w DNA
DNA ligase
DNA ligase: molecular glue. Seals nicks in between Okazaki fragments by enzymatically creating a phosphodiester bond btwn two adjacent bases. NOT an DNAP…cannot add bases
Bloom syndrome
Bloom syndrome: defect in DNA ligase. Predisposition to cancer.
Three mechanisms in place to ensure accuracy in replication:
1)
2)
3)
1) DNAPIII: has error rate of 1/100,000
2) DNA proofreading activity (3’-5’ exonuclease): 1/10,000,000
3) post replication DNA repair (DNAPII) 1/1 billion
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Eukaryotic DNA replication:
- many more origins
- more DNAPs
- slower rate of replication (due largely to the high levels of DNA packaging)
What is the problem w replicating the ends of linear eukaryotic xsomes?
You lose a little bit of the ends of the linear xsomes w each round of DNA replication as a result of removing the RNA primer. The primer on the end cannot be replaced w DNA bc there is not a preexsisting 3’OH group that the DNAP can add bases to.
Hayflick limit
Hayflick limit: the shrinkage of xsomes associated w cellular aging and programmed cell death
The enzyme __________ fights back against shrinkage by binding to the ends of the xsomes and adding on tandem copies of the telomere repeat sequence.
The enzyme telomerase fights back against shrinkage by binding to the ends of the xsomes and adding on tandem copies of the telomere repeat sequence.
Telomerase _____________ xsomes.
Telomerase elongates xsomes.
Telomerase: ribonucleoprotein- has and RNA component and a protein component
Telomerase: ribonucleoprotein- has and RNA component and a protein component
Telomerase is an _______ dependent DNA polymerase.
Telomerase is an RNA dependent DNA polymerase. Aka it uses its own RNA as a template to make DNA copy.
Two types of DNA recombination:
1)
2)
1) homologous: common in germ lined cells in meiosis I
2) non-homologous: illegitimate recombination. Common in somatic cells
* widely accepted model is the Holliday model for homologous recombination
The Holliday model 1) 2) 3) 4) 5) 6)
1) recognition and alignment
2) ssDNA breakage
3) crossing over and strand evasion
4) joining of ends by DNA ligase
5) branch migration and heteroduplex formation
6) cleavage and resolution
Two possible resolution products for Holliday recombination:
1)
2)
1) horizontal: non crossover recombination, patched, on same linkage phase as parents
2) vertical: cross over recombination, spliced, opposite linkage phase
What is DNA’s primary function?
DNA’s primary function is to store all genetic info in a stable form such that info is not lost when transmitted to daughter cells.
DNA sequence is actually a code that….
DNA sequence is actually a code that when deciphered directs the assembly of amino acids into the formation of proteins.
Although DNA stores the information, it is not the primary template used to direct the synthesis of proteins. It’s the _______.
It’s the mRNA that serves as the template for protein synthesis.
__________________ describes the process of taking the stored info in DNA to direct the synthesis of proteins.
Gene expression describes the process of taking the stored info in DNA to direct the synthesis of proteins.
Two main processes involved w gene expression:
1)
2)
1) transcription: the synthesis of mRNA from a DNA template to produce an mRNA molecule that is complimentary and anti parallel to the DNA template
2) translation: synthesis of a polypeptide from an mRNA template
Transcription
Transcription: the synthesis of mRNA from a DNA template to produce an mRNA molecule that is complimentary and anti parallel to the DNA template
Translation:
Translation: synthesis of a polypeptide from an mRNA template
Central dogma of molecular biology: flow of genetic info w/in the cell
DNA -transcription—>mRNA-translation–>protein
- DNA dep RNAPs. -ribosomes&tRNAs - DNA replication - DNA depen DNAPs: uses/copies DNA template
Transcription:
Transcription: 5’-3’ synthesis of mRNA from a dsDNA template. Although the mRNA is transcribed from dsDNA, only ONE strand of the DNA serves as a template
Finishing touches:
1)
2)
Finishing touches:
1) removal of RNA primer and replacement w DNA
2) joining of fragments, called Okazaki fragments, on lagging strand using enzyme DNA ligase
