basic principles of heredity - classical vs molecular genetics

molecular genetics

• most traits involve multiple genes plus environmental factors

• every trait is a product of nature and nurture

plant height proteins

• giberellin - controls height of plants

• GA-3 oxidase - in functional state allows plants to grow tall

• LE allele codes for GA-3 oxidase in its functional form so giberellin is activated - grow tall

• le allele codes for GA-3 oxidase in its non-functional state so giberellin remains inactivated - plant short

• heterozygous - enough of GA-3 oxidase in functional state produced by LE allele so giberellin activated and plant grows tall

haploinsufficiency

• when not enough of one product is produced to express the phenotype

probability - molecular genetics

• recombination - some genes on the same chromosome will segregate randomly unless they are located close together on the chromosome

• means than even when genes are located on the same chromosome, alleles are inherited independently

dominance - molecular genetics

• protein function is the key to understanding how different alleles cause trait variation - absence of a protein being produced can prevent an allele being expressed

co-dominance - molecular genetics

• no universal mechanism for dominance - about the function of proteins that different alleles code for and how they interact

• incomplete dominance - neither of 2 alleles is completely dominant over the other

complex traits

• most traits influenced by multiple genes

• genes code for proteins that interact in complex ways

• traits inherited with unpredictable patterns