5. DNA Sequencing Flashcards
1
Q
When were the first DNA sequencing methods made?
A
1970s
2
Q
2 early methods of DNA sequencing
A
- Sanger
- Maxam and Gilbert
3
Q
How does Sanger sequencing work?
A
- uses natural mechanism of DNA synthesis
- where DNA dependent DNA polymerase migrates along one strand of complementary base pairs to an elongating second strand
- done in vitro with single stranded DNA template, DNA polymerase and diff nucleotides
- include natural bases and labelled dideoxynucleotides
- once incorporated, polymerase can’t add new bases and chain terminates
- then you can see the length of chains and nature of label and can work out sequence of bases of DNA strand
- ddNTPs originally were labelled with radioactivity but now are fluorescent
4
Q
The first genome was sequenced in …
A
1977
5
Q
What came after Sanger’s sequencing methods?
A
- read lengths become shorter
- mainly now based on conducting millions of different reactions simultaneously
- short sequences stitched together bioinformatically to gain longer sequences or a whole genome
6
Q
How has sequencing helped to seperate diff bacterial genomes?
A
- sequence diff strains of E.Coli or Salmonella etc and work out genes present in every strain
- see which genes are in all strains of a species and which aren’t
- termed core genome of species
- see which genes are only in certain ones and may encode virulence factors and what makes certain strands pathogenic
7
Q
What is the total gene content of all strains of a species called?
A
pan genome
8
Q
Define ‘pan genome’
A
total gene content for all strains of a species
9
Q
Define ‘core genome’
A
genes present in all strains of a species of bacteria
