Genomes

The Structure of Genomes

  • A genome is the complete set of genetic material present in an organism.
  • It contains all the information needed to build and maintain that organism.
  • The genome includes both the genes and the non-coding sequences of the DNA.
  • The human genome, for example, is made up of about 3 billion base pairs of DNA.
  • Humans have an estimated 20,000-25,000 genes which code for proteins.

DNA and Genetic Code

  • The genome is made up of DNA (deoxyribonucleic acid). DNA contains four different bases: A, C, G, and T.
  • The order of these bases forms the genetic code, providing instructions for protein synthesis.
  • A gene is a segment of DNA that codes for a specific sequence of amino acids, which together make a specific protein.
  • Different organisms have varying numbers of genes. The size of an organism’s genome and the number of genes don’t directly correlate with the organism’s complexity.

Genomes and Inheritance

  • Every individual, except for identical twins, has a unique genome that contributes to physical and biological differences.
  • Each person’s genome is a combination of DNA inherited from their parents, half from the mother and half from the father.
  • Genetic variation occurs through mutations, recombination during sexual reproduction, and environmental influences.
  • These variations can lead to differences in characteristics, known as traits, between individuals of the same species.

Genomes and Evolution

  • Over long timescales, changes in genomes can lead to new species in a process called evolution.
  • Comparative genomics, the study of different species’ genomes, can provide insight into evolutionary relationships.
  • By comparing genome sequences, scientists can deduce how closely related different species are, and perhaps predict which genes are responsible for certain traits.

Genomic Sequencing

  • Genomic sequencing is the process of determining the complete DNA sequence of an organism’s genome.
  • The first full human genome sequence was completed in 2003 by the Human Genome Project.
  • Today, genomic sequencing is a powerful tool in biomedical research and is increasingly used in medicine for diagnosis and treatment decision-making.
  • Due to ethical issues related to privacy and discrimination, the use of genomic data must be carefully managed.