Chapter 14: Human Inheritance

1. Chapter 14:Human Inheritance Section 14-3: Studying the Human Genome

2. Manipulating DNA • The SMALLEST human chromosome contains 50 million bases • DNA is a HUGE molecule that is difficult to manipulate • In the 1970s, scientists discovered they could use natural enzymes to analyze DNA • Today, scientists read DNA base sequences by using enzymes to cut, separate, and replicate DNA base by base

3. Cutting DNA • Easy to extract/separate DNA from other macromolecules • In order to analyze, DNA molecules must be cut into smaller pieces • Restriction enzymes are produced by bacteria – they cut DNA molecule at specific sequences of nucleotides into precise pieces called restriction fragments • Hundreds of Res, each cuts at different sequence

4. Cutting DNA • Ex: EcoRI recognizes GAATTC • Cuts between G and A bases, leaving “sticky ends” • Can bond to complementary bases

5. Separating DNA • Gel electrophoresis is used to separate DNA fragments that have been cut with restriction enzymes • Can then analyze DNA in pieces • Steps: • Mixture of DNA fragments placed at the end of a pourous gel • Electric voltage applied to gel, causing DNA molecules to move toward positive end (DNA has a neg charge) • Smaller DNA fragments move faster/farther • Creates a banding pattern • Stains used to make bands visible • Remove fragments and study

7. Reading DNA • Read = sequence • Single-stranded DNA put in test tube with DNA polymerase and four bases (ATGC) • DNA polymerase uses unknown strand as template to make new strands • Some of the added bases have dyes attached, • Each time a labeled base is added, replication stops • End up with a series of fragments that are color coded • Separate fragments with electrophoresis, colored bands on the gel tell exact sequence of bases on DNA • Automated

9. The Human Genome Project • Began in 1990 – US and several other countries • Goals: • Sequence all 3 billion base pairs of human DNA • Identify all human genes • Sequence genomes of model organisms to interpret human genome • Develop new technology to support research • Explore gene functions • Study human variation • Train future scientists

10. The Human Genome Project • How they did it: • Break genome into pieces • Sequence pieces, identify markers • Used computer for analysis • Current research explores data gained from HGP – looking for genes, identifying their function

11. Comparing Sequences • Most of every person’s DNA is the same • On average, one base in every 1200 with not match • These are called SNPs (single nucleotide polymorphisms) • Collections of SNPs are called halpotypes – haploid gentoypes • Project called HapMap began in 2002 to indentify all the haplotypes

12. Sharing Data • Copies of human/other genomes available on the internet • New field borne – bioinformatics • Combines molecular biology with information science • Also new field called genomics – the study of whole genomes, including genes and their functions

13. What have we learned? • Complete working copy of human genome in 2000 • Full reference sequence in 2003 • Contains 3 billion nucleotide bases • Only 2% encodes for proteins • Found genes/sequences associated with diseases/disorders • Identified 3 million locations of SNPs • New technologies, medical applications