Inheritance Basic

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Slide 1

Inheritance

Slide 2

Some features are in two forms

Some people have ear lobes and others do not.

e.g.

Slide 3

A gene controls how ear lobes develop.

There are two versions of the gene.

They are called alleles.

E

which produces ears with lobes.

e

which produces ears without lobes.

and

Slide 4

The genes are in our cells.

Where are they kept?

In the nucleus

Slide 5

The genes are on long, string-like things called

chromosomes

Slide 6

We have 46 of them in our cells.

What do you notice about them?

Slide 7

All our chromosomes are in pairs

Where did we get each one from?

half came from mum

and half came from dad

Slide 8

This means that genes are in pairs

Because…

E

E

Genes are on chromosomes.

Slide 9

So .

forgetting all those chromosomes

you might have

two lobe alleles

EE

two no lobe alleles

ee

or

one of each allele

Ee

but you definitely have

2

Slide 10

However!

Slide 11

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

Slide 12

We can use these facts

to make predictions

about the features that

children will inherit from

their parents.

Slide 13

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?

Slide 14

mum

dad

parent’s

genotype

EE

ee

sex cell’s

alleles

E

e

But… does the child have ear lobes?