Class Notes (839,394)
Canada (511,324)
Biology (6,826)
Lecture 18

Biology 2581B Lecture 18: Lec 18 – Modifications and Bioinformatics

9 Pages

Course Code
Biology 2581B
David R Smith

This preview shows pages 1,2 and half of page 3. Sign up to view the full 9 pages of the document.
Lecture 18 – Modifications and Bioinformatics What are genetic modifications? - Significant genetic alterations that are often not apparent or obvious given the primary DNA sequence alone o Impact genetic information but may not know about them if just looking at the sequence - Nonstandard codes o If know the sequence for a gene and but don’t know what code is used, could incorrectly interpret how the information is expressed - Knowing the code is crucial Cox 1 amino acid sequence (vertebrate mitochondrial code vs. standard genetic code) - Cox1 gene in mitochondrial genome - AA sequence for the gene: translate the gene using the nonstandard vertebrate mitochondrial code - If you didn’t know about the nonstandard codes and were asked to translate the gene for the amino acid sequence, would’ve had a different amino acid sequence o A sequence with many stop codons inserted throughout - Genetic modifications are crucial and if you don’t know about them, they can push you down another road RNA editing - Genetic modification - Modification that changes the underlying sequencing information - Thinking of genetics and central dogma, expect gene sequence to get transcribed to get an mRNA - mRNA should reflect perfectly the DNA sequence from which it was derived o Only difference we expect is T become Us o Usually holds true but it is not ALWAYS true Spikemoss Selaginella mitochondrial genome - Plant (gene within an intron within a gene) – resurrection plant “Rose de Jericho” (stays dry) - Peculiar editing in mitochondrial compartment + genome - Looking at the DNA sequence of a gene and the corresponding transcript (mRNA sequence) for the coding sequence o Everything looks right except the Ts have become Us o This is what we expect - In this organism in this genome, after the transcript is generated, a lot of the Cs get turned post transcriptionally to Us (not all) - RNA editing/post-transcriptional editing: tweaking the RNA sequence and changing it from what it was - Like the nonstandard code, if didn’t know about editing sites that are introduced, can get the wrong amino acid sequence o AUG is different than ACG, giving a different amino acid - 1000s of C-to-Us editing sites in the mitochondrial genome o Found in chloroplast genome too Selaginella - Cox 1 – DNA and RNA sequence - Cox1 gene in the plant - RNA sequence is derived from the DNA sequence o Ts became Us – the only different o Some Cs get post-transcriptionally edited to Us ▪ Not all of them get turned to U - DNA gets turned to RNA, then something changes all C to U o Substitutional RNA editing - > 200 C-to-U editing sites in a single gene - In mitochondrial genome, the RNA does not reflect the DNA o Impacts the products that get made from the genes o DNA  RNA  AA sequence ▪ AA sequence for cox1 based on DNA: would’ve gotten a different sequence than the one with the edited sites - Deduced amino acid sequence (using standard code) o After taking into account the editing sites, the sequence is different - For every site that gets edited, need proteins to bind to the RNA and the complex is called an edidosome o Protein complex with the purpose to edit sites o Edits and changes to U - Don’t use the same complex to edit all of the sites - Every Us that gets edited, needs a SEPARATE PROTEIN COMPLEX o Complexes are similar o Each site has its own complex that gets encoded and edits the site - For every site edited, need a unique protein complex - Dozens to hundreds of proteins to make 1 protein - Take the gene and want to turn it into cytochrome C oxidase subunit I o Making 1 protein requires 100s of other proteins to bind to the RNA to fix it Tree of land plants & green algae - Changing RNA sequence through editing is found in all land plants and their chloroplast and mitochondrial genomes o Evolved in one group and don’t see it in others o Occurred independently in trypanosomes too - Various degrees of RNA editing in mitochondrial and chloroplast genomes RNA editing - RNA editing has evolved many times independently throughout the tree of life Trypanosomes - mtDNA (kinetoplast DNA) o Polycistornic nuclear transcription o Weird DNA in chain mail structure - Mitochondrial genome: o Maxi circles encode the genes o Mini circles without genes - Mini circles serve to edit the genes o Us are inserted or deleted from the transcript - Uracil insertion/deletion RNA editing - DNA  RNA: Ts changed to Us o Editing occurs after transcription o Editing mechanism inserts and deletes Us ▪ Occurs repeatedly - In a single gene, can have hundreds of U’s can be inserted and deleted from a transcript - Selaginella: if had DNA sequence of cox 1 gene, could figure out its cox 1 even though it doesn’t look right o Can identify it from DNA o Editing was substantial but not enough to dissolve the information at the DNA level - Trypanosome: so many Us inserted and deleted that if you were given DNA, would never know what we were looking at o Wouldn’t know it was a gene sequence until RNA was present - Deletions, insertion sand editing is done by transcripts of the mini circles - Transcripts: o mRNA from maxi circle genes: long o Mini circles give little mRNAs that guide the editing - Long mRNA from maxi circles
More Less
Unlock Document

Only pages 1,2 and half of page 3 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.