The document summarizes key concepts in molecular genetics including DNA repair mechanisms using nucleases and DNA polymerase, telomeres and their role, transcription which involves copying DNA into mRNA with RNA, differences between RNA and DNA like the sugar and nucleotide uracil, codons and their role in specifying amino acids, and Marshall Nirenberg's experiments concluding that DNA is a universal genetic code and mRNA acts as a template from its 5' to 3' end.

1. 11/12/08
Lecture 28 - Molecular Genetics
− Repair mechanism for DNA
− Nucleases: Enzymes that can recognize mistakes.
− They can remove the problem.
− DNA polymerase can make a correction.
− In skin (xeroderma pigmentosa), highly sensitive to being in the sun (radiation).
− They don't have the nucleases.
− Telomeres: the ends of DNA in an eukaryotic cell.
− The coding can be repeated up to 1,000 times.
− The coding does nothing.
− Telomerase: Restores telomeres to their original length; acting only in gametes.
− Transcription: The organic process whereby the DNA sequence in a gene is copied into mRNA.
− This process involves RNA.
− There are many types of RNA.
− RNA contains the sugar, ribose, instead of deoxyribose.
− In RNA, the nucleotide, Uracil, replaces the nucleotide, Thymine, from DNA.
− Codon: A sequence of three bases that typically codes for a particular amino acid.
− There are 65 possible combinations of codons.
− All codons are used (duplication).
− Marshall Nirenberg assembled synthetic mRNA and put them onto ribosomes. He wanted to see what amino
acid/protein would form.
− He concluded:
− DNA (the coding) is universal.
− In transcription, only one side of the DNA is transcribed to mRNA.
− mRNA is called the template strand of the coding strand.
− mRNA works from the 5' end to the 3' end.
- Promoter region: Where RNA polymerase binds up-stream to start transcription.