BIO 7: April 27-30 Preview
Multiple Allelism: there can be more than 2 forms of a gene, because there are many ways to change the DNA and protein, and different protein activities may cause different phenotypes.
e.g. In humans: IO = seq in DNA coding for an inactive protein for attaching A and B antigens
Possible Genotypes:
Possible Phenotypes:
Gene Interaction is something else Mendel did not know about. Several genes can determine one trait because many proteins encoded by genes work together in metabolic pathways to produce one final outcome.
e.g. Human hair color is determined mainly by 2 pairs of genes, which are on different pairs of chromosomes
D codes for active protein for making dark pigment and d codes for inactive protein for making dark pigment
R codes for active protein for making red pigment and r codes for inactive protein for making red pigment
When dark pigment is present, you cannot see the red pigment.
Genotypes: D_ R_ D_ rr dd R_ dd rr
Phenotypes:
What is the expected phenotypic ratio from a mating of Dd Rr x Dd Rr?
Complex Genetic Traits are due to many pair of interacting genes + the environment
e.g. height, weight, IQ test performance
monozygotic twins
dizygotic twins
concordance; the percentage of the time a pair of individuals shows the same form of the trait
CONCORDANCE FOR
TRAIT MONOZYGOTIC TWINS DIZYGOTIC TWINS
Schizophrenia 55% 10%
Alcoholism 55% 28%
Blood Type 100% 66%
Epilepsy 72% 15%
Diabetes 65% 18%
Cleft Lip 42% 5%
Death by infection 1% 1%
[Which of the traits above is a complex genetic trait, a simple genetic trait, not determined by genes?]
Genes and Environment Interact: one genotype may produce different phenotypes in different environments.
[Are cuttings genetically identical or different?]