PRE FI DNA SEQUENCING Flashcards
Refers to the ORDER OF THE NUCLEOTIDES in the DNA molecule.
DNA SEQUENCE
Applications of DNA sequencing in medical
laboratory:
o Detection of mutation
o Typing microorganisms
o Identifying human haplotypes
o Designating polymorphism
o Treatment strategies
SEQUENCING METHODS:
DIRECT DETERMINATION OF THE ORDER, or sequence of nucleotides in a DNA polymer.
Most specific and direct method for identifying genetic lesions (mutations)/ polymorphisms.
Types:
1. Manual sequencing (chemical (Maxam-Gilbert & Sangers sequencing)
2. Automated fluorescent sequencing (dye primer & dye terminator sequencing)
A. RNA sequencing
B. Next-generation sequencing
C. Direct sequencing: manual and automated
D. Bisulfite DNA sequencing
E. Pyrosequencing
C. Direct sequencing: manual and automated
MANUAL SEQUENCING:
Allan M. Maxam & Walter Gilbert
Requires a ds/ss version of the DNA region to be sequenced with 1 end radioactively labeled ( 32P)
Sequencing proceeds in 4 SEPARATE REACTIONS
Template: LABELED FRAGMENT
A. Chemical (Maxam-Gilbert) Sequencing
B. Dideoxy Chain Termination (Sanger) Sequencing
Chemical (Maxam-Gilbert) Sequencing
Addition of a _________ =
ssDNA would break at specific nucleotides
strong reducing agent (10% piperidine)
Chemical (Maxam-Gilbert) Sequencing:
o Sequence = bands
o Lane in which the band appeared = ID of
the nucleotide
o Sequence is read from the ____ to the ______ of the gel
BOTTOM (5’ end) to the TOP (3’ end) of the gel
Chemical (Maxam-Gilbert) Sequencing:
Run times of short fragments (up to 50 bp)?
1-2 hours
Chemical (Maxam-Gilbert) Sequencing:
Run times of Long fragments (>150 bp) ?
7-8 hours
MANUAL SEQUENCING:
Frederick Sanger
Uses DIDEOXYNUCLEOTIDES(ddNTPs) to determine the order/sequence of nucleotides in a nucleic acid
PRIMER complementary to DNA to be sequenced
Product detection of sequencing:
o Primer is attached at 5’ end to a 32P-
/fluorescent dye-labeled nucleotide
o Incorporate 32p/35S-labeled dNTPs in the
nucleotide sequencing reaction mix
(INTERNAL LABELING)
ddNTPs are added, terminating the DNA synthesis
(chain termination)
o Lack OH = 5’-3’ phosphodiester bond
cannot be established to incorporate a
subsequent nucleotide.
Components: Mixed in 4 reaction tubes
1. DNA template (PCR product)
2. Radioactivity-labeled primer
3. Enzyme (DNA polymerase)
4. dNTPs (all 4)
5. Buffer (20mM EDTA, formamide, gel tracking/
loading dyes)
6. Different ddNTPs in each of the 4 tubes
A. Chemical (Maxam-Gilbert) Sequencing
B. Dideoxy Chain Termination (Sanger) Sequencing
Dideoxy Chain Termination (Sanger) Sequencing
SEQUENCING REACTION of Dideoxy Chain Termination (Sanger) Sequencing?
thermal cycler (cycler
sequencing
Automated reading of DNA sequence ladder
requires fluorescent dyes (4 distinct colors) to label
primers/ sequencing events
1. Fluorescein
2. Rhodamine
3. Bodipy (4,4-difluoro 4-bora-3a-diaza-s indacene)
Fluorescent dyes can be distinguished by AUTOMATED SEQUENCERS
Approaches (to label fragments according to their terminal ddNTP): DYE PRIMER and DYE TERMINATOR SEQUENCING
Automated Fluorescent Sequencing
4 different fluorescent dyes are attached to 4
separate aliquots of the sample.
Dye molecules are attached to the 5’ end of the primer = 4 versions of the same primer with
different dye labels.
Products are LABELED AT THE 5’ end using the dye color associated with the ddNTP at the end of the fragment.
DYE PRIMER OR DYE TERMINATOR SEQUENCING?
Dye Primer Sequencing
1 of the 4 fluorescent dyes attached to each of the
ddNTPs.
All 4 sequencing reactions are performed in the
same tube.
Products fragments are LABELED AT THE 3’ end.
DYE PRIMER OR DYE TERMINATOR SEQUENCING?
Dye Terminator Sequencing
4 sets of sequencing products in each reaction are loaded onto a single gel lane/ capillary.
Fluorescent dye colors distinguish which nucleotide is at the end of each fragment.
Fluorescent detection equipment yields results as electropherogram.
Base calling: process of bases ID in a sequence by sequencing software.
Automated Electrophoresis
Software Programs Used to Analyze and Apply Sequence Data:
- Compares an input sequence with all sequences in a selected
database
A. FASTA FASTQ
FAST-All derived from FAST-P (protein) and
FAST-N (nucleotide) search algorithms
Biological data with quality score
B. BLAST Basic Local Alignment Search Tool
C. Phred
D. GRAIL Gene Recognition and Assembly Internet Link
BLAST Basic Local Alignment Search Tool
Software Programs Used to Analyze and Apply Sequence Data:
- Finds gene-coding regions in DNA sequences
A. FASTA FASTQ
FAST-All derived from FAST-P (protein) and
FAST-N (nucleotide) search algorithms
Biological data with quality score
B. BLAST Basic Local Alignment Search Tool
C. Phred
D. GRAIL Gene Recognition and Assembly Internet Link
GRAIL Gene Recognition and Assembly Internet Link
Software Programs Used to Analyze and Apply Sequence Data:
- Rapidly aligns pairs of sequences by sequence patterns rather
than individual nucleotides
A. FASTA FASTQ
FAST-All derived from FAST-P (protein) and
FAST-N (nucleotide) search algorithms
Biological data with quality score
B. BLAST Basic Local Alignment Search Tool
C. Phred
D. GRAIL Gene Recognition and Assembly Internet Link
FASTA FASTQ
FAST-All derived from FAST-P (protein) and
FAST-N (nucleotide) search algorithms
Software Programs Used to Analyze and Apply Sequence Data:
- Reads bases from original trace data and recalls the bases,
assigning quality values to each base
A. FASTA FASTQ
FAST-All derived from FAST-P (protein) and
FAST-N (nucleotide) search algorithms
Biological data with quality score
B. BLAST Basic Local Alignment Search Tool
C. Phred
D. GRAIL Gene Recognition and Assembly Internet Link
Phred
Software Programs Used to Analyze and Apply Sequence Data:
- Identifies single- nucleotide polymorphisms (SNPs) among the traces and assigns a rank indicating how well the trace at a site matches the expected pattern for an SNP
A.Polyphred
B. TIGR Assembler The Institute for Genomic Research
C. Phrap Phragment Assembly Program
D. Factura
A.Polyphred
Software Programs Used to Analyze and Apply Sequence Data:
- Uses USER - SUPPLIED and internally computed data quality information to improve accuracy of assembly in the presence of repeats
A.Polyphred
B. TIGR Assembler The Institute for Genomic Research
C. Phrap Phragment Assembly Program
D. Factura
Phrap Phragment Assembly Program
Software Programs Used to Analyze and Apply Sequence Data:
- Developed by TIGR as an assembly tool to BUILD A CONSENSUS SEQUENCE from smaller-sequence fragments
A.Polyphred
B. TIGR Assembler The Institute for Genomic Research
C. Phrap Phragment Assembly Program
D. Factura
TIGR - Assembler The Institute for Genomic Research
Software Programs Used to Analyze and Apply Sequence Data:
- Identifies sequence features such as flanking vector sequences, restriction sites, and ambiguities
A.Polyphred
B. TIGR Assembler The Institute for Genomic Research
C. Phrap Phragment Assembly Program
D. Factura
Factura
Software Programs Used to Analyze and Apply Sequence Data:
- Provides MUTATION and SNP DETECTION and analysis, pathogen
subtyping, allele identification, and sequence confirmation
A.Matchmaker
B. SeqScape
C. Assign
SeqScape
Software Programs Used to Analyze and Apply Sequence Data:
- Identifies alleles for haplotyping
A.Matchmaker
B. SeqScape
C. Assign
Matchmaker & Assign
SEQUENCING METHODS:
Determines a DNA sequence W/OUT HAVING TO MAKE A SEQUENCING LADDER
Relies on the generation of light (luminescence) when nucleotides are added to a growing DNA strand.
No gels, fluorescent dyes, ddNTPs
Reaction mix components:
1. ssDNA template
2. Sequencing prime
3. Sulfurylase
4. Luciferase
5. Substrates: adenosine-5’-phosphosulfate (APS) and luciferin
6. 1 of the 4 dNTPs is added to predetermined
order of the reaction
A. RNA sequencing
B. Next-generation sequencing
C. Direct sequencing: manual and automated
D. Bisulfite DNA sequencing
E. Pyrosequencing
Pyrosequencing
SEQUENCING METHODS:
AKA METHYLATION-SPECIFIC SEQUENCING
Chain termination sequencing designed to DETECT METHYLATED SEQUENCING CYTOSINE NUCLEOTIDES
2-4 ug of genomic DNA is cut with restriction enzymes to facilitate denaturation.
DNA is denatured (97C for 5 mins) and exposed to bisulfate solution (sodium bisulfite, NaOH,
hydroquinone) for 16-20 hours.
o Cytosines are deaminated –> uracil
o 5-methylcytosines are unchanged
o Can be detected by Sanger sequencing/ pyrosequencing
A. RNA sequencing
B. Next-generation sequencing
C. Direct sequencing: manual and automated
D. Bisulfite DNA sequencing
E. Pyrosequencing
Bisulfite DNA sequencing