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Genomic Sequencing 8a - Coggle Diagram
Genomic Sequencing 8a
Genomic sequencing
- (real first step) In order to obtain the sequence, it must first be cut into more manageable sections
Step 1: Use of restriction endonucleases
- A restriction endonuclease (or restriction enzyme) is an enzyme that recognises specific short sequences (4-8 base pairs) of DNA nucleotides called restriction sites.
e.g EcoR1 recognises GAATTC, BamH1 recognises GGATCC
2) Sequencing DNA
- A portion of the DNA is chosen to be sequenced
- Copies are made of the DNA strand using DNA polymerase, primer and nucleotides
- Modified nucleotides are also used – they are tagged
with a flourescent dye
- When a modified nucleotide is added, DNA synthesis
stops and we can now see where it is.
- The strands are separated using electrophoresis.
--In this process the shortest fragments travel the longest
distance
- This provides a map for us to see the whole genome
Step 3: Genome shotgun approach
- Now the sequence has been determined, the pieces have to put back together.
- This is done by computer analysis of the sequences looking for sections that over-lap.
- For each fragment of DNA get the DNA sequence.
- The sequence is analysed looking for overlaps.
- Then it is ordered into one overall sequence using computer software.
Bioinformatics
- The statistical analysis of DNA sequences using computer programmes to identify base sequences and to compare sequences to similar known genes.
Genomics
- Genomics is the study of an organism's genes, including gene interactions between genes and between genes
and the environment.
- The sequences of disease-causing organisms, pest species, and model organisms have been sequenced
for these purposes.
- As well as sequencing the human genome, scientists have determined the genome sequence of a range of other organisms.
- They have found that many genes are highly conserved across different species.
Model Organisms
- they possess genes equivalent to human genes and can be easily studied in the lab
e.g E. coli - Bacterium that is an important model for molecular biology, genetics and biotechnology.
e.g Fruit fly that has many genes in common with those that
cause disease in humans
e.g Mus musculus - Mouse that possesses many genes present in humans
Genomes
Comparative genomics
- Comparison of many genomes has revealed that DNA sequences of important genes are highly similar (conserved) from one organism to the next.
- e.g. genes coding for proteins involved in aerobic respiration, or for key enzymes.
-
Differences in genome
- Variation in DNA sequence in the form of a single base pair is called single nucleotide polymorphism (SNP).