Heredity and inheritance
The chapter has used two words that sound alike and are not interchangeable. It is worth separating them now, before the human examples begin.
Heredity
The transmission of characteristics from parents to their offspring. The process, considered as a whole.
Inheritance
A characteristic being received by an individual from its parents. What happens to one organism.
What actually gets transmitted
Nothing visible passes from parent to child. What passes is a set of instructions, and the route is short:
- The gametes — the ovum and the sperm — each carry a set of chromosomes.
- Those chromosomes carry genes, which are lengths of DNA.
- At fertilisation the two sets combine, and the zygote has a complete pair of every gene — one allele from each parent.
Genetics is the study of both
The branch of biology that studies heredity and the variation it produces is called genetics. Mendel began it by counting pea plants; the same rules are now used to trace human characteristics through families.
Everything you inherited arrived in two cells
All the genetic information a person receives came in one ovum and one sperm — nothing else was transmitted. Every cell in your body was built from copies of what those two carried.