Genotype
Genotype: refers to the genes an individual possesses / an individualߢs genetic make-up.
Phenotype
Phenotype: refers to the observable traits or characteristics shown by the individual; these traits / characteristics are due to the combined effect of genes and environment.
A recent study showed that Alzheimer’s disease may be partly inherited.
(1)
(1) (Total 2 marks)
John’s father suffered from Alzheimer’s disease. John is keen to get genetically tested to see if he will develop Alzheimer’s disease.
Explain why John’s genotype will not reveal whether he will suffer from Alzheimer’s disease.
the genetic test reveals the genotype not the phenotype
• John’s genotype will only reveal his set of genes (not their interaction with the
environment)
• a genetic test will only reveal if he is predisposed to suffering Alzheimer’s disease
but will not reveal whether he will develop/suffer from the disorder
• environmental factors may contribute to the disorder (it depends on an interaction
between inherited factors and the environment.
Rita and Holly are identical twins who were separated at birth. When they finally met each other at the age of 35, they were surprised at how different their personalities were. Rita is much more social and out-going than Holly.
Use your knowledge of genotype and phenotype to explain this difference in th
Holly and Rita have identical genotype as they are MZ twins.
• They have the predisposition to develop the same personalities as each other
unless another factor(s) intervenes.
• For them to have developed different personalities over time, this must have been influenced by being in different environments.
• Their phenotypes – personalities achieved – are different, presumably because Rita was encouraged to be sociable and lively and Holly was not
