GENETICS AND INHERITANCE:
GENOTYPE Vs PHENOTYPE:
GENOTYPE – characteristics of the genes themselves
E.g. heterozygous / homozygous or whether the genes are recessive/ dominant
Genotype = Rr or RR
PHENOTYPES – physical characteristic of the organism
E.g. Hair colour, eye colour, hereditary diseases
Phenotype = red hair
COMPLETE DOMINANCE:
Occurs when there is dominant and recessive alleles present, the dominant gene
will always dominate the recessive therefor always appearing in the phenotypes
of the organism.
The only time that a recessive gene will be present in the phenotype in complete
dominance is when the genotype is homozygous for the recessive gene
For example B is dominant allele for brown eyes and b is the recessive allele for
blue eyes.
BB = brown eyes
Bb = brown eyes
bb = blue eyes
Mendel’s laws:
- Mendel’s law of segregation: during meiosis, allele pairs separate so that the
gametes have a single allele for each characteristic.
- Mendel’s law of dominance: in a cross of parents that are pure for contrasting
traits, only the dominant trait will appear in the phenotype. Recessive alleles
will always be masked by dominant alleles.
- Mendel’s law of independent assortment: the alleles of different genes
segregate randomly and independently of on another during gamete formation
, CO-DOMINANCE:
Occurs when two alternative dominant alleles are present in the genotype and
are fully observed in the phenotype of the organism.
A dog that has black fur mates with a dog that white fur and both black and white
alleles are dominant then their off spring will have both black and white fur
combined.
INCOMPLETE DOMINANCE:
Occurs when a dominant alleles does not quite mask the affects of9 the
recessive gene completely.
Instead both the dominant and recessive genes will combine and for a mixture of
the two.
Example a white rose is pollinated from a red rose, if there was incomplete
dominance occurring, the offspring would be pink flowers.
Complete dominance Co- dominance
Incomplete dominance
GENOTYPE Vs PHENOTYPE:
GENOTYPE – characteristics of the genes themselves
E.g. heterozygous / homozygous or whether the genes are recessive/ dominant
Genotype = Rr or RR
PHENOTYPES – physical characteristic of the organism
E.g. Hair colour, eye colour, hereditary diseases
Phenotype = red hair
COMPLETE DOMINANCE:
Occurs when there is dominant and recessive alleles present, the dominant gene
will always dominate the recessive therefor always appearing in the phenotypes
of the organism.
The only time that a recessive gene will be present in the phenotype in complete
dominance is when the genotype is homozygous for the recessive gene
For example B is dominant allele for brown eyes and b is the recessive allele for
blue eyes.
BB = brown eyes
Bb = brown eyes
bb = blue eyes
Mendel’s laws:
- Mendel’s law of segregation: during meiosis, allele pairs separate so that the
gametes have a single allele for each characteristic.
- Mendel’s law of dominance: in a cross of parents that are pure for contrasting
traits, only the dominant trait will appear in the phenotype. Recessive alleles
will always be masked by dominant alleles.
- Mendel’s law of independent assortment: the alleles of different genes
segregate randomly and independently of on another during gamete formation
, CO-DOMINANCE:
Occurs when two alternative dominant alleles are present in the genotype and
are fully observed in the phenotype of the organism.
A dog that has black fur mates with a dog that white fur and both black and white
alleles are dominant then their off spring will have both black and white fur
combined.
INCOMPLETE DOMINANCE:
Occurs when a dominant alleles does not quite mask the affects of9 the
recessive gene completely.
Instead both the dominant and recessive genes will combine and for a mixture of
the two.
Example a white rose is pollinated from a red rose, if there was incomplete
dominance occurring, the offspring would be pink flowers.
Complete dominance Co- dominance
Incomplete dominance
