Some features are in two forms
Some people have ear lobes and others do not.
A gene controls how ear lobes develop.
There are two versions of the gene.
They are called alleles.
which produces ears with lobes.
which produces ears without lobes.
Where are they kept?
In the nucleus
The genes are on long, string-like things called
We have 46 of them in our cells.
What do you notice about them?
All our chromosomes are in pairs
Where did we get each one from?
half came from mum
and half came from dad
Genes are on chromosomes.
forgetting all those chromosomes
you might have
two lobe alleles
two no lobe alleles
one of each allele
but you definitely have
Sex cells are special when it comes to chromosomes and genes.
They only have one of each, not the usual two.
Why is this?
Sex cells are designed to join together and so .
1 + 1 = 2
We can use these facts
to make predictions
about the features that
children will inherit from
Lets pretend .
that a man without ear lobes
and a woman with lobes
will soon have their first baby
Will the baby have ear lobes?
But… does the child have ear lobes?