1. Mendelian Inheritance

2. Conclusions:
Purple colour is dominant
White colour is recessive
The cause of the white colour
is not diluted, but co-exists
with the purple colour

3. Mendel’s Model
Alternative versions of genes account for variations in inherited characteristics
Purple or white flowers
For each characteristic, an organism inherits two alleles – one from each parent
If two alleles at a locus differ, one is dominant and the other is recessive
The two alleles separate during gamete formation

4. Helpful definitions Gene Locus Allele
Segments of DNA on a chromosome in the genome that specify the sequence of a protein
Locus
The specific location of a gene on a chromosome in the genome
Allele
any one of a number of versions of a gene occupying a given locus
Each cell has 2 copies of a chromosome
Therefore there are two possible alleles for every gene

7. More definitions Homozygous Heterozygous Genotype Phenotype Pleiotropy
Organism with a pair of identical alleles
Heterozygous
Organism with two different alleles for a particular gene
Genotype
The genetic make-up of an individual
Phenotype
The displayed traits of an individual
Pleiotropy
occurs when a single gene influences multiple phenotypic traits

8. Genotype vs. Phenotype

9. Performing a Testcross

10. Independent Assortment

11. But….then there is incomplete dominance

12. Or….co-dominance…or even multiple alleles

13. Epistasis - the gene at one locus alters the phenotype resulting from another
gene at a separate locus
B – black
b – brown
C – colour
c – no colour
Black (B) is dominant
Colour (C) is dominant
cc will be albino (no colour)

14. Quantitative trait locus
a region of DNA that is associated with a particular phenotypic trait
underlie continuous traits - the trait could have any value within a range (e.g. height)
a single phenotypic trait is usually determined by many genes
QTLs are often found on different chromosomes
Nature vs. Nurture

15. Pedigree Charts