Genotype, Phenotype, and Allele Combinations
In GCSE Biology inheritance, it's essential to understand the difference between genotype and phenotype:
Definition: Genotype is the combination of alleles that causes a characteristic, while phenotype is the expressed characteristic.
For example, in mice:
- Genotype BB or Bb results in a phenotype of black fur
- Genotype bb results in a phenotype of brown fur
This concept is crucial for solving GCSE Biology inheritance exam questions.
Allele combinations can be classified as:
- Homozygous: when both alleles are the same e.g.,BBorbb
- Heterozygous: when the alleles are different e.g.,Bb
Highlight: Understanding homozygous and heterozygous combinations is key to predicting inheritance patterns.
An example of genetic inheritance is red-green color blindness, which is a recessive characteristic. The alleles are represented as R dominant,notcolorblind and r recessive,colorblind.
Example: A person with unaffected vision could have the genotype RR or Rr, while a color-blind individual would have rr.
These concepts are frequently tested in genetics GCSE Biology Edexcel and other exam boards.