Notes on the Human Genome and DNA Fingerprinting

Objectives

  • Describe components of the human genome.

  • Explain how forensic scientists use DNA fingerprinting.

  • Discuss the application of the human genome in diagnosing diseases.

The Human Genome Project (HGP)

  • Overview: Completed in 2003, the HGP aimed to determine the sequence of approximately three billion nucleotides in human DNA and identify about 20,000-25,000 human genes.

  • Significance:

    • If all nucleotides were lined up, the length would be equivalent to the distance from Los Angeles to Panama.

    • Analysis of data will continue for decades; it has informed studies in various organisms like the fruit fly, mouse, and E. coli to aid in developing necessary technologies.

Sequencing the Human Genome

  • Process:

    1. Each of the 46 human chromosomes was cleaved using various restriction enzymes.

    2. Fragments were combined with vectors forming recombinant DNA, cloned, and sequenced using automated machines.

    3. Computers then analyzed overlapping fragments to create a continuous sequence.

  • Key Insights:

    • Less than 2% of nucleotides code for proteins; much of the genome consists of noncoding sequences.

    • Noncoding regions may have potential regulatory roles or other unknown functions.

Understanding the Genetic Code

  • Decoding: The decoding process can be likened to reading an unformatted book:

    • Without capitalization or punctuation, scientists need to decode and understand the genetic information.

  • Noncoding Sequences: These consist of repetitive sequences with no direct function, contributing to structural complexity without coding for proteins.

DNA Fingerprinting

  • Definition: A technique for analyzing unique DNA fragments cut by restriction enzymes.

  • Applications:

    • Identification of victims and suspects in criminal cases.

    • Determining paternity.

    • Identifying deceased soldiers.

  • Process:

    1. DNA is isolated from crime scenes and suspects.

    2. Selected markers are amplified using Polymerase Chain Reaction (PCR).

    3. Amplified DNA is separated using gel electrophoresis for comparison.

Identifying Genes

  • Current Status: Many human genes are still not understood.

  • Research Techniques:

    • Use of computer analysis combined with recombinant DNA technology to uncover gene functions.

    • Open Reading Frames (ORFs):

    • Found in simpler organisms, with sequences containing at least 100 codons, starting with a start codon and ending with a stop codon.

    • ORF analysis successfully identifies over 90% of genes in bacteria and yeast.

    • More complex organisms, such as humans, require advanced algorithms for gene identification.