Lecture 26 Flashcards
What are the deviations from simple Mendelian ratios?
- Lethal Alleles
- Polymorphic genes
- Incomplete dominance
- Co-dominance
- Epistasis
What are lethal alleles?
Alleles that do not live when produced, change the ration from 3:1 to 2:1
What is a polymorphic?
1 gene that has more than 2 alleles
What is incomplete dominance?
When one allele isn’t completely dominant over the other
results in an inbetween heterozygous
Self fertilisation shows the original colour is 1:2:1 ratio
What is co-dominance?
Both phenotypes exsist side by side within each organism
Both phenotypes are shown in the heterozygous
What is Epistasis?
When one gene affects the action of another
What is a polygenic trait?
When a phenotype is affected by many genes
continuous (non-discrete) traits eg weight, height, skin colour
What can be affected by the environment in an organism?
- Nutrition
- Height/Weight
- Life expectancy
- Disease
What can be affected by the environment in an organism?
- Nutrition
- Height/Weight
- Life expectancy
- Disease
What is pleiotropy?
When a single cell affects many phenotype traits
What are examples of pleiotropy?
- Sickle cells cause many symptoms
- One gene affects eye colour/wing length/body hair in a Dropsophila
