A genome is all the hereditary information held by an organism. This includes both expressed and non-expressed genetic information. In most organisms, it is stored in DNA; however, retroviruses store it in RNA, another type of nucleic acid. The information is encoded in the form of triplets of organic molecules called nucleotides.
Eukaryotes (including humans) have the following types of genomic material:
- the nuclear genome: Information found inside the nucleus of a cell.
- the mitochondrial genome: Information found in the mitochondria
- plants also have the chloroplast genome (human and animals obviously do not).
Chloroplast and mitochondrial genomes are somewhat remotely similar to the genomes of the independent organisms (while significantly smaller by size and number of genes). These separate genomes are used as evidence for the endosymbiotic hypothesis, although they can also be explained by creationist models. Most of the genetic information is stored in the nuclear genome, where also many mitochondrial and chloroplast proteins are encoded.
In addition, organisms often inherit other material from their parents, such as proteins, RNA molecules, and other chromosomal factors like methyl groups attached to certain base pairs. These are regarded as the purview of epigenetics.
The Human Genome Project mapped the genome of humans (Homo sapiens) in a 13-year study, and is considered one of the marvels of modern human medicine and biology. All of the information is stored in a database. It is expected that the results of the project will allow scientists to predict how genetics influences drug interaction with the body, and lead to target specific drugs.
Genomes of other species have been recorded as well, such as mice, chimpanzees and yeast. The mouse genome sequence from the C57BL/6J strain has about 30,000 genes, and 99% of them have direct counterparts in humans.
The chimpanzee represented the first non-human primate sequenced. The differences in the chimpanzee and human genomes are small, with 99% of the DNA sequence preserved. The differences can be classified in terms of differences in local single nucleotide substitutions, insertions, deletions and repetitions of sequences. A relatively large number of difference between the chimpanzee and human genomes are not due to substitutions. When this is taken into account, humans and chimpanzees still share 96% of their sequence, and are genetically closer than rats and mice.
Instead of seeing DNA as evidence for evolution, creation scientists see DNA as confirming evidence of God's divine plan. He has encoded into DNA His blueprints for making life. It is thus no surprise that the DNA of similar animals shares many sequences. DNA can be seen as a successful prediction of creation science.
- Collins, Francis S. and McKusick, Victor A. Implications of the Human Genome Project for Medical Science JAMA, 2001;285:540-544, 7th February 2001.
- Matthews, Michael, DNA—what does it prove? Answers in Genesis, 25th April, 2003.