English for

 
Polymerase Chain Reaction 
Often, DNA analysis necessitates focusing on one or more specific regions of the genome. It also 
frequently involves situations where only one or a few copies of a DNA molecule are available for further 
investigation. Most procedures, such as gel electrophoresis, require far more than these amounts. 
Polymerase 
chain reaction
(PCR) is a technique used to rapidly increase the number of copies of specific regions of DNA 
for further analyses (Figure 52). PCR employs a specific form of DNA polymerase, the enzyme responsible for 
DNA replication, as well as other short nucleotide sequences known as primers that base pair to a specific 
portion of the DNA being replicated. In laboratories, PCR is used for a variety of purposes. These include: 1) 

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the identification of the owner of a DNA sample left at a crime scene; 2) paternity analysis; 3) the comparison 
of small amounts of ancient DNA with modern organisms; and 4) determining the sequence of nucleotides in 
a specific region. 
 
Figure 52.
Polymerase chain reaction, or PCR, is a technique for producing many copies of a specific 
DNA sequence using a special type of DNA polymerase
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3.4 Reading Resource #2:
Whole Genome Sequencing 
Despite significant advances in the medical sciences in recent years, many diseases continue to 
confound doctors, and researchers are using whole genome sequencing to get to the bottom of the problem. 
Whole genome sequencing
is a process that determines the DNA sequence of an entire genome. When there 
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( Fowler, S.,Roush, R. & Wise, J. (2017) 
Concepts in Biology, 
Chapter 9, -Pp. 226-228 OpenStax, 
https://openstax.org/details/books/concepts-biology
 

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is a genetic basis at the heart of a disease, whole genome sequencing is a brute-force approach to problem 
solving. Several laboratories now offer services for whole-genome sequencing, analysis, and interpretation. 
In 2010, whole genome sequencing was used to save the life of a young boy whose intestines were 
riddled with mysterious abscesses. The child underwent several colon operations with no success. Finally, a 
whole-genome sequence revealed a flaw in an apoptosis-controlling pathway (programmed cell death). A bone 
marrow transplant was used to overcome this genetic disorder, resulting in the boy's cure. He was the first 
person to be diagnosed successfully using whole genome sequencing. 
The first genomes to be sequenced, such as those belonging to viruses, bacteria, and yeast, were smaller 
in terms of the number of nucleotides than the genomes of multicellular organisms. The genomes of other 
model organisms, such as the mouse (
Mus musculus
), the fruit fly (
Drosophila melanogaster
), and the 
nematode (
Caenorhabditis elegans
) are now known. A great deal of basic research is performed in