Lecture, chapter 5 - DNA replication

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Today we finished chapter 5, on DNA replication. We went into details of how the lagging strand is synthesized, forming the Okazaki fragments, thanks to DNA looping, which allows for it's synthesis even though the helicase and polymerase III-dimer complex travels in the same direction of the replication fork. We added how the RNA primers are degraded and the Okazaki fragments are joined, by the action of ribonuclease H, DNA polymerase I, and DNA ligase.

We then discussed how DNA transcription proceeds in eukaryotes, what's the role of telomerase in reparing telomeres after each round of replication, and the differences between the action of polymerases in prokaryotes and eukaryotes.

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Module 2, Lab 06a - Nested PCR of the GAPC gene of Arabidopsis thaliana

Arabidopsis thaliana

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Today we started the exercise in which students will learn the basics of a nested PCR. We will work with the gene that encodes one of the GAPDH isomers, GAPC, in Arabidopsis thaliana, the model organism of plants. Some people call it "the fruit-fly of plants".

GAPDH is an enzyme in charge of catalyzing one of the reactions in glycolysis. There are several nuclear genes that encode GAPDH isomers (proteins with different amino acid sequences but with the same function), and we are targeting the gene GAPC in the A. thaliana genome. We ran a first round of PCR, with our initial primers, and on Wednesday after Christmas break we will run the second round, with the nested primers.

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Module 1, Lab 05 - Size Exclusion Chromatography (SEC)

Today we did the agarose gel electrophoresis for lab 04 (detection of genetic modification in crops), using 2% agarose gels.

Then we did lab 05, size exclusion chromatography (SEC), in which a sample mix of hemoglobin and vitamin B12 were separated by size by column chromatography.

Once the procedure was finished we discussed agarose gel interpretation, specifically for labs 02 and 03.

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Lecture, chapter 5 - DNA replication

Monday, December 14, 2009

Today we started chapter 5, on DNA replication.

We discussed some of the generalities of how DNA is duplicated in a cell, and introduced the concept of replication fork. We are listing the enzymes involved in the replisome as we mention each one of their roles in the process.

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