21.2 dna sequencing and analysis

Question 1

What is the first step in dna sequencing

Answer 1

The dna is mixed with a primer, DNA polymerase, excess of normal nucleotides and terminator bases
This mixtures is then placed in a thermal cycler

Question 2

What is a thermal cycler

Answer 2

Equipment that is also used in pcr that rapidly changes temperature at programmes intervals in repeated cycles

Question 3

What happens when the mixture is placed into the thermal cycler in dna sequencing

Answer 3

At 60 degrees DNA polymerase starts to build up new dna strands by adding nucleotides with complemtary bases to single strand dna template

Question 4

What do the terminator bases do in dna sequencing

Answer 4

Each time they are incorporated the synthesis of dna is terminated as no more bases can be added
This results in many dna fragments of different lengths
They create all the possible dna chains

Question 5

What happens in dna sequencing when all possible chains are made

Answer 5

The chains are seperated according to their length by capillary sequencing
Termanator bases identify the final base on each fragment

Question 6

What are capillary tubes used for in dna sequencing

Answer 6

They carry out capillary sequencing and put the dna fragments in order according to length
The order of bases in the capillary tubes shows the sequence of the new complementary strand of dna

Question 7

What happens when the DNA sequence has been made by capillary sequencing

Answer 7

Info is fed into a computer that resembles the genomes by comparing all the fragments and finding the areas that overlap between them