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How
we receive DNA from our parents
People have long realised that children inherit physical traits
from their parents, but it was not until relatively recently
that we understood that heredity is due to DNA.
Most human cells hold a full copy of that person’s DNA.
The exceptions are the sex cells – the male’s sperm
and the female’s egg – each of which only contains
half a set. The DNA is stored in thread-like structures called
chromosomes.
During reproduction, the sex cells fuse together. The two
half-sets of chromosomes, one from the mother and the other
from the father, are thus combined to give the full set of
genetic information needed to build another human being.
The new cell now divides and re-divides rapidly, forming a
cluster of cells. This develops into an embryo, which develops
into a foetus, and so on. As a cell divides, the DNA it contains
is copied, so that each new cell receives a complete copy
of the DNA present in the original.
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