Genomes and Their Evolution

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It is constructed by cutting a DNA molecule into many short fragments and arranging them in order by identifying overlaps

Slide 11

Sequencing machines are used to determine the complete nucleotide sequence of each chromosome

A complete haploid set of human chromosomes consists of 3.2 billion base pairs

Slide 12

Whole-Genome Shotgun Approach to Genome Sequencing

The whole-genome shotgun approach was developed by J. Craig Venter in 1992

This approach skips genetic and physical mapping and sequences random DNA fragments directly

Powerful computer programs are used to order fragments into a continuous sequence

Slide 13

Fig. 21-3-1

Cut the DNA

into overlapping

fragments short enough

for sequencing

1

2

Clone the fragments

in plasmid or phage

vectors.

Slide 14

Fig. 21-3-2

Cut the DNA

into overlapping

fragments short enough

for sequencing

1

2

3

Clone the fragments

in plasmid or phage

vectors.

Sequence each

fragment.

Slide 15

Fig. 21-3-3

Cut the DNA

into overlapping

fragments short enough

for sequencing

1

2

3

4

Clone the fragments

in plasmid or phage

vectors.

Sequence each

fragment.

Order the

sequences into

one overall

sequence

with computer

software.

Slide 16

Both the three-stage process and the whole-genome shotgun approach were used for the Human Genome Project and for genome sequencing of other organisms

At first many scientists were skeptical about the whole-genome shotgun approach, but it is now widely used as the sequencing method of choice

A hybrid of the two approaches may be the most useful in the long run

Slide 17

Concept 21.2 Scientists use bioinformatics to analyze genomes and their functions

The Human Genome Project established databases and refined analytical software to make data available on the Internet

This has accelerated progress in DNA sequence analysis

Slide 18

Centralized Resources for Analyzing Genome Sequences

Bioinformatics resources are provided by a number of sources:

National Library of Medicine and the National Institutes of Health (NIH) created the National Center for Biotechnology Information (NCBI)