Human Genome Projectby: Amanda Mosello

What is the Human Genome Project?

• created in 1990, by the National Institutes of Health and the US Department of Energy

• Goals– identify all the genes in the human DNA (@ 80,000)– determine the sequences of the 3 billion chemical bases that

make up human DNA– store this information in databases

– develop tools for data analysis – address the ethical, legal, and social issues (ELSI)

Outline

• Basics

• Sequencing

• Mapping

• Current Status

• ELSI

Basics

• DNA– a double helix structure

– each strand consists of• one sugar

• one phosphate

• a nitrogenous base (A,T,C,G)

– held together by weak bonds between the bases of each strand, forming base pairs (bp)

Basics (cont.)• Genes

– specific sequence of nucleotide bases, whose sequences carry the information required for constructing proteins

• Proteins– are large, complex molecules

made up of long chains of subunits called amino acids

– Codons - specific sequence of three DNA bases that directs the cell protein-synthesizing machinery to add specific amino acids

Basics (cont.)

• Chromosomes– genes arranged along the

chromosomes

– contains equal parts of protein and DNA

– one set of 23 from each parent

– stained, under a light microscope, the variations in bases can be distinguished

Why is all this important?

• A genome is all the DNA in an organism

• The particular order of the bases within the DNA underlies all of life’s diversity

• Learning about the effects of the variations in DNA can lead to revolutionary new ways to diagnose, treat, and someday prevent the thousands of disorders

• Besides providing clues to understanding human biology, learning about nonhuman organisms' DNA sequences, can lead to an understanding of their natural capabilities that can be applied toward solving challenges in health care, energy sources, and environmental cleanup.

What is DNA sequencing?

• the process of determining the exact order of the 3 billion bases that make up the 24 different human chromosomes

• this will reveal the estimated 80,000 genes as well as the regions controlling their expressions into proteins

• about 9.02% of the genome has been sequenced• this will result in DNA sequencing maps

• Gel-based

– sequencers in development use tiny (capillary) tubes to run standard electrophoretic separations.

• Gel-less

– DNA chips-DNA fragments bound toa solid surface

– mass spectrometry-separation of fragments

Techniques and Technology

• Chromosomes, which range in size from 50 million to 250 million bases, must first be broken into much shorter pieces

• Each short piece is used as a template to generate a set of fragments that differ in length from each other by a single base

• The fragments in a set are separated by gel electrophoresis

Mapping the Human Genome

• Involves dividing the chromosomes into smaller fragments that can be propagated and characterized

• Also involves ordering them to correspond to their respective locations on the chromosomes

• Mapping describes the order of genes or other markers and the spacing between them on each chromosome

– The current human genetic map has about 1000 markers, or 1 marker spaced every 3 million bp, with an estimated 100 genes lie between each pair of markers.

Mapping Strategies

• Markers must be polymorphic to be useful in mapping

• Polymorphisms are variations in DNA sequence

• Variations within exon sequences can lead to observable changes

• Most variations occur within introns and have little or no effect on an organisms appearance or function, yet they are detectable at the DNA level and can be used as markers

Mapping Strategies (cont.)

• Markers- any inherited physical or molecular characteristic that differs among individuals and is easily detectable in the laboratory is a potential genetic marker

• Meiotic Recombination- during the normal production of sperm and egg cells, DNA strands occasionally break and rejoin in different places on the same chromosome or on the other copy of the same chromosome

• Two markers located near each other on the same chromosome will sometimes be passed together from parent to child

• The closer the markers are to each other the more tightly linked they are, and the less likely to be separated by spontaneous chromosome rearrangements

Why Map?

• Locate inherited diseases– cystic fibrosis, sickle cell disease, Tay- Sachs disease,

fragile X syndrome, and myotonic dystrophy.

• Recombinant Technology– in vitro radiation- induced chromosome fragmentation

and cell fusions

Where are they now?• Genetic Map - 1 cM published in 1994 - completed by

2003

• Physical Map - 52,000 STS’s mapped - completed by 2003

• DNA Sequence - 180 Mb human and 111 Mb nonhuman - finish 1/3 of human sequence by 2001, complete in 2003

• Gene Identification - 30,000 EST’s mapped - full length cDNA’s complete by 2003

• Model Organisms - Completed sequence for E.coli and yeast - 80% of C.elegans, 9% of Drosophilia, 12,000STS’s mapped for a mouse - complete sequence by 2008

ELSI

Ethical, Legal, and Social Issues• Fairness in the use of genetic information

• Privacy and confidentiality

• Psychological impact and stigmatization

• Genetic testing

• Reproductive issues

• Clinical issues

• Commercialization

• Conceptual and philosophical implications