Download Patterns of inheritance

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.