1. Bellwork: What is the human genome project. What was its purpose
Bellwork: What is the human genome project? What was its purpose? Was it a success?

2. Studying the human genome
Section 14.3

3. What techniques are used to study DNA?
After discovering the importance of DNA, reading it seemed to be impossible
The smallest chromosome contains nearly 50 million base pairs
The job was made easier through the use of natural enzymes
Enzymes can be used to cut, separate and replicate DNA base by base
Allows scientists to read the base sequences in DNA from any cell

4. How do you cut DNA?
Differences in the chemical makeup make DNA relatively easy to separate and extract from other cells and tissues
Entire DNA molecules are too large – they need to be cut to size
Many bacteria produce enzymes that do this – restriction enzymes
Even the largest DNA molecules are cut into precise pieces - restriction fragments
A few hundred bases in length
Each restriction enzyme cuts DNA at different sequences of nucleotides

5. Separating DNA – gel electrophoresis
Gel electrophoresis is used to to separate and analyze the differently sized fragments
DNA fragments are placed at one end of a porous gel
When electric current is applied, DNA Molecules (which are negatively charged) move towards the positive end of the gel
The smaller the fragment the faster it moves
End up with DNA bands based on fragment size
Stains can make these bands visible

6. Reading the DNA
DNA fragments are placed in test tube with DNA polymerase alongside the 4 nucleotide bases
Unknown strand is used as a template
A small number of bases have a chemical dye attached to them
When these bond replication stops
End up with a series of color coded fragments of different length
Separate by gel electrophoresis again
Order of colored bands tells exact sequence of bases on DNA
Can be automated by computers – speeding everything up

7. Human Genome project
A 13 year international effort with the goal of sequencing all 3 billion base pairs of human DNA, and identifying every human gene
Other goals included
Sequencing genomes of model organisms to interpret human DNA
Develop technology to support the research
Explore gene functions
Study human variation
Train scientists
DNA sequencing was basis for human genome project
First DNA was broken into manageable pieces
By determining base sequences in widely separated regions they were able to use these regions as markers

8. Sequencing and identifying genes
Once DNA is marked they used a method called shotgun sequencing
DNA is cut into random fragments
Base sequences are determined
Computer programs analyze this data, and find areas of overlap
Link fragments by linking overlapping areas
Reading is not the same as understanding
Scientists look for promoters to identify specific genes
Sequences that separate introns and exons , and stop codons also all help in identifying genes

9. Comparing sequences
Most of the DNA of unrelated individuals matches base for base with each other
Only 1 base in 1200 will not match
These are single base differences – Single nucleotide polymorphisms (SNPs/snips)
Certain sets of SNPs occur together time and again – haplotypes (haploid genotypes)
HapMap project started in 2002 to identify these in more detail

10. Sharing data Human genome project was completed in 2003
Copies of human genome are freely available on the internet
More data is added on a daily basis
Lead to a new fields of study:
Bioinformatics – Where IT meets biology
Genomics – study of whole genomes, including genes and their functions

11. What we learnt
Only 2 percent of the human genome contains instructions for synthesizing proteins
Many chromosomes contain large areas with few genes
Half the genome is made up of DNA from viruses and other genetic elements
Project was a great success
Pinpointed genes
Associated particular sequences in genes with numerous diseases and disorders
3 millions SNPS identified
Opened up new avenues of research – biotechnology

12. Issues raised What happens next?
Who owns and controls genetic information?
Who should have access to this information? Insurance companies?
In 2008 US congress made it illegal to discriminate on the basis of genetic information
As science progress new laws may follow
What happens next?
Potential for tailoring treatments for diseases to specific individuals

13. Does it stop with DNA?
DNA is coiled around protein clusters called nucleosome to form chromatin
Where chromatin is compact genes are switched off
Where chromatin opens up gene expression is enhanced
Process of opening and closing controlled by enzymes that leave chemical marks, which are affected by stress, diet and disease
These chemical marks are epigenetic – they are above the level of the genome
They do not affect the base sequence, but affect gene expression
These marks can be passed on to offspring