6.1.2 Patterns of Inheritance Flashcards
Chi squared
Compare expected phenotype ratio (from the punnet table) with the observe phenotype ratio. Show whether differences are significant or due to chance.
How to do chi squared
-Punnet table
- Total number of offspring/ratio total x predicted ratio
- Observed is found
- Observed - Expected
- Square numbers
- Divide numbers by the Expected results
- Add both numbers (each phenotype) together
- Use 0.05 and degrees of freedom (number of phenotypes - 1)
- If the value is higher than the critical value, reject the null hypothesis
- If the value is lower than the critical value, accept null hypothesis
Continuous Variation
- Quantitative
- No distinct categories
- Polygenic
- Environmental and genetic factors
- E.g. height
Discontinuous Variation
- Qualitative
- Categories
- Monogenic
- Genetic factors
- E.g. gender
Phenotypic Variation
There is variation within a population.
Influenced by genotype, environment or both.
Genotype only
- E.g. skin colour (continuous)
- E.g. blood group (discontinuous)
Environmental only
- E.g. etiolation (plants growing spindly due to lack of sun)
- E.g. chlorosis (environmental factors cause lack of chlorosis and so yellow plants)
Both genotype and environment
- E.g. height
- E.g. body mass
Gene
Sequence of bases on dna molecule that codes for a functional protein which results in a characteristic.
Allele
A version of a gene, you have two from each of the homologous chromosomes. B or b.
Genotype
The alleles an organism has.
BB, Bb or bb.
Phenotype
The characteristics produced by the genotype.
Dominant
Appears in phenotype even if there’s only one copy. If B is for brown and b is blue eyes then BB and Bb would be brown.
Recessive
Appears in phenotype if two are present. bb would be blue.
Codominant
Alleles can both be expressed
if dominant. CR and CW can produce roan colouring in cows.
