Genome Sequencing - Shotgun Sequencing

Question 1

23.5 learning objective

Answer 1

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Question 2

23.5 learning objective

Answer 2

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Question 3

23.5 learning objective

Answer 3

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Question 4

23.5 learning objective

Answer 4

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Question 5

genome sequencing projects

Answer 5

research endeavors with the ultimate goal of determining the sequence of DNA bases of the entire genome of a species

Question 6

what doe genome sequencing of a human include?

Answer 6

22 autosomes, 2 sex chromosomes, and mitochondrial genome

Question 7

shotgun sequencing

Answer 7

DNA fragments to be sequenced are randomly generated from larger DNA fragments, about 1500 bp in length

Question 8

how does shotgun sequencing work?

Answer 8

1) DNA fragments are randomly generated
2) genomic DNA is slated and broke down into smaller segments (1500 bp)
3) the DNA fragments are randomly sequenced from the genome
4) by chance, some of the fragments overlap

Question 9

what is the most efficient and inexpensive way to sequence genomes?

Answer 9

shotgun sequencing

Question 10

what is an advantage to shotgun sequencing?

Answer 10

doesn’t require extensive mapping

Question 11

what is a disadvantage of shotgun sequencing?

Answer 11

does waste some time sequencing the same region of DNA more times than needed

Question 12

how do researchers decide ow many fragments to sequence?

Answer 12

p = e ^ -m

• p is the probability that bases will be left unsequenced
• e is the natural log 2.72
• m is the number of bases sequenced by dividing the total genome size (divide what has been sequenced by genome size)

Question 13

what are the specific steps of shotgun sequencing?

Answer 13

1) purify DNA by breaking the cells open and adding phenol or chloroform while DNA is still in the water
2) sonicate DNA to break it into small fragments of about 2000 bp
3) clone DNA fragments into vectors to produce a library
4) subject clones to the procedure of dideoxycytidine DNA sequencing
5) use tools of bioinformatics to identify genes