Genome - Matt Ridley Flashcards
Preface
The human genome - the complete set of human genes - comes packaged in 23 separate pairs of chromosomes.
Every protein is a translated gene. A gene is a coded recipe.
Life
The language of DNA is considerably simpler than English, since it has only an alphabet of 4 letters: A, C, G and T.
Anything that can use the resources of the world to get copies itself made is alive; the most likely form for such a thing to take is a digital message - a number, script or word.
The less entropy a system has, the more information it contains. Life is digital information, written in DNA.
A ribosome is a machine whose job is to translate DNA recipes into proteins. It is proteins that enable DNA to replicate.
Cooks need recipes, but recipes also need cooks. Life consists of the interplay of 2 kinds of chemicals: proteins and DNA.
RNA is a chemical substance that links the 2 worlds of DNA and protein.
Whereas the “genotype” is the genetic makeup of an organism, the phenotype is how genetic and environmental influences come together to create an organism’s physical appearance and behaviour.
The 3-letter words of the genetic code are the same in every creature. CGA means arginine and GCG means alanine - in bats, in beech trees, in bacteria.
The unity of life is an empirical fact.
Species
“Man with all his noble qualities still bears in his bodily frame the indelible stamp of his lowly origin.”
Chimpanzees have 24 pairs of chromosomes; so do gorillas and orang utans. Among the apes, humans are the exception; we have 23 pairs. 2 ape chromosomes have fused together in us (Chromosome 2 is formed from this fusion).
Pope John Paul II argued that between ancestral apes and humans, there was an ‘ontological discontinuity’ - a point at which God injected a human soul into animal lineage. Thus can the Church be reconciled to evolutionary theory. The genes for the soul lie near the middle of chromosome 2.
The pope notwithstanding, the human species is by no means the pinnacle of evolution.
Evolution has no pinnacle and there is no such thing as evolutionary progress.
Our brains are the most complicated machines on the planet. But complexity is not everything, and it is not the goal of evolution. Every species on the planet is unique. Uniqueness is a commodity in oversupply.
Apart from the fusion of chromosome 2, visible differences between chimp and human chromosomes are few and tiny. In 13 chromosomes no visible differences of any kind exist.
We are, to a 98% approximation, chimpanzees and vice versa.
Are chimpanzees genetically more like gorillas (97%) or human beings (98%)?
There is no bone in the chimpanzee body that I do not share. There is no known chemical in the chimpanzee brain that cannot be found in the human brain.
Natural selection is the process by which genes change their sequences. In the process of changing, these genes laid down a record of our 4 billion year biography as a biological lineage. A record of our past is etched into our genes.
It is mind-bogging to imagine how small differences in linear digital instructions can direct the two per cent difference between a human body and a chimpanzee body.
Genes are recipes for both anatomy and behaviour.
No matter how the calculation is done, the big point still holds: humans, chimpanzees, and bonobos are more closely related to one another than either is to gorillas or any other primate. From the perspective of this powerful test of biological kinship, humans are not only related to the great apes – we are one. The DNA evidence leaves us with one of the greatest surprises in biology: the wall between human, on the one hand, and ape or animal, on the other, has been breached. The human evolutionary tree is embedded within the great apes.
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