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 GenotypeGenotype descriptionPhenotype RRHomozygous dominantTongue roller RrHeterozygousTongue roller rrHomozygous recessiveCan’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.