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Human Genomics
Chapter 5
Human Genomics
• Human genomics is the study of the human genome. It involves
determining the sequence of the nucleotide base molecules all the
way along the DNA and then relating this genetic information about
genes to their functions.
Human Genome Project
• Started in 1986 (USA and UK) but officially ‘started’ in 1990,
Europe and Japan joined in 1992
• Completed in 2003 – under budget and 2 years early
• The sequence is not that of one person, but is a composite
derived from several individuals. Therefore, it is a
"representative" or generic sequence. To ensure anonymity of
the DNA donors, more blood samples (nearly 100) were collected
from volunteers than were used, and no names were attached to
the samples that were analysed. Thus, not even the donors knew
whether their samples were actually used.
• Also sequenced yeast and animals used in medical research e.g.
zebra fish and rats.
• What were the aims of the human genome project?
• To identify all the approximately 20,000-25,000 genes in human
DNA.
• To find where each gene is located
• To determine the sequences of the 3 billion chemical base pairs
that make up human DNA.
• Store this information in databases.
• Estimated time 15 years. (started in 1980)
• Estimated cost US$3 billion
• The DNA Fragments of various lengths(each with its modified
nucleotide and its unique fluorescent tag) are separated using
electrophoresis. The order of the nucleotides in the original DNA can
then be worked out from the fluorescent dye that is used.
• Usually a computer working as an automated sequence analyser,
detects the four fluorescent dyes processes this information quickly
and displays the sequence of bases in the DNA sample.
Single Nucleotide Polymorphism(SNP)
SNP maps
• Scientists have managed to catalogue more than a million SNPs. They
believe that an SNP map will help them identify and understand the
workings of genes associated with disease.
• Some SNPs may indicate the likelihood of a person developing a
particular illness.
Alzheimer’s Disease
• One of the genes associated with this disease is called ApoE
(Apolipoprotein E)
• The gene is affected by two SNPs and different combinations of these
produce three different forms of the gene (Apo E2, Apo E3 and Apo
E4).
• Research has shown that inheritance of the ApoE4 allele increases the
chance of Alzheimer’s disease whilst inheritance of the Apo E2 allele
makes the person less likely to develop the condition.
Personal Genome Sequence
Amplification and Detection of DNA
Sequences- Polymerase Chain Reaction (PCR)
Amplification and Detection of DNA
Sequences- Polymerase Chain Reaction (PCR)
Amplification and Detection of DNA
Sequences- Polymerase Chain Reaction (PCR)
The first cycle of replication
produces two identical
molecules of DNA
Amplification and Detection of DNA
Sequences- Polymerase Chain Reaction (PCR)
During the second cycle,
the two DNA molecules
from the first cycle split
and then nucleotides are
added. By the end of the
second cycle, four identical
molecules are produced..
This will continue and the
population of DNA
molecules will grow
Amplification and Detection of DNA
Sequences- Polymerase Chain Reaction (PCR)
By. the end of the second
cycle four identical DNA
molecules are made.
DNA Probes and Arrays
Medical and Forensic Applications of Amplified
DNA- Genetic testing for Cystic Fibrosis
Crime Scenes
Forensic Scientists make use of
the PCR reaction to amplify DNA
samples at a crime scene. DNA
samples are taken from the
victim and the suspects are also
amplified. Next components of
the samples are separated using
gel electrophoresis and then
compared.
Paternity Disputes