PATTERNS OF INHERITANCE

Variation

Continuous variation – results in genetic information contributed by several genes (Eg. Height in humans because a range of heights occurs)

Variation

Continuous variation – results in genetic information contributed by several genes (Eg. Height in humans because a range of heights occurs)

Discontinuous variation – have one value or another and do not show a range (Eg. Seeds of pea plants being either green or yellow)

Genotype & Phenotype

The genetic information on the two alleles present in an individual is called the genotype (the letters)

Genotype & Phenotype

The genetic information on the two alleles present in an individual is called the genotype (the letters)

The expression (physical characteristic) of these two alleles in the individual is called the phenotype.

Genotype & Phenotype

The genetic information on the two alleles present in an individual is called the genotype (the letters)

The expression (physical characteristic) of these two alleles in the individual is called the phenotype.

The phenotype that results from a genotype is determined by which allele is dominant and which allele is recessive.

Genotype & Phenotype

The genetic information on the two alleles present in an individual is called the genotype (the letters)

The expression (physical characteristic) of these two alleles in the individual is called the phenotype.

The phenotype that results from a genotype is determined by which allele is dominant and which allele is recessive.

Dominant – always expressed in the phenotype (it masks the presence of the recessive)

Genotype & Phenotype

The genetic information on the two alleles present in an individual is called the genotype (the letters)

The expression (physical characteristic) of these two alleles in the individual is called the phenotype.

The phenotype that results from a genotype is determined by which allele is dominant and which allele is recessive.

Dominant – always expressed in the phenotype (it masks the presence of the recessive)

Recessive – only expressed in the phenotype when there are two recessive alleles.

Genotype

We use capital letters for dominant alleles and lower case letters for recessive alleles.

Genotype

We use capital letters for dominant alleles and lower case letters for recessive alleles.

When both alleles are the same (RR or rr) the individual is homozygous for that trait

Genotype

We use capital letters for dominant alleles and lower case letters for recessive alleles.

When both alleles are the same (RR or rr) the individual is homozygous for that trait

When the alleles are different (Rr) the individual is heterozygous for that trait.

Genotype

We use capital letters for dominant alleles and lower case letters for recessive alleles.

When both alleles are the same (RR or rr) the individual is homozygous for that trait

When the alleles are different (Rr) the individual is heterozygous for that trait.

** Capitals are always written first**

Example: rolling tongues

Genotype Genotype description

Phenotype

RR Homozygous dominant

Tongue roller

Rr Heterozygous Tongue roller

rr Homozygous recessive

Can’t roll tongue

Pure breeders

An individual homozygous for a trait is known as a pure breeder because they can only pass on one kind of allele to their offspring.

Pure breeders

An individual homozygous for a trait is known as a pure breeder because they can only pass on one kind of allele to their offspring.

EG – Homozygous dominant RR can only pass on allele R to their gametes; homozygous recessive rr can only pass on allele r to their gametes.