Human GenomicsChapter 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 exponentially. By this means a tiny quantity of DNA can be greatly amplified and provide sufficient material for forensic and medical purposes.

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