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How characteristics are inherited

We inherit dominant or recessive genes from our parents
If there is a dominant gene in a pair that characteristic is
Recessive characteristics only show if there are two
recessive genes in a pair

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Example of Dominant and Recessive genes

Brown hair allele is dominant ( B )
Blonde hair allele is recessive ( b )

If the male has brown hair and is homozygous ( BB ) and the
female has blond hair and is homozygous ( bb ) what colour hair

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Inherited disorders

Most inherited disorders are caused by faulty genes, most
of which are recessive

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Example of Inherited disorders

Allele for no cystic fibrosis is dominant ( C )
allele for cystic fibrosis is recessive ( c )

A carries does not have cystic fibrosis because they are
heterozygous for the diseases ( Cc ), will their children have
cystic fibroses ?

C c

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Mutations are caused by the miss ­ copying of the gene
sequence which DNA replicates, divides and copies

This can be caused be several factors :

Spontaneously at random
Diseases e.g. Rubella ( German measles )
Nuclear radiation

Mutations are usually harmful but can sometimes be

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Genetic Word and definitions

A chromosome is a long string of DNA containing genes

DNA contains genes ; made from 4 basis G, C, A and T

A gene is a section of DNA that makes a particular protein ;
determines character

An allele is a…


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