Genetics, Hooray! Flashcards
genetic interaction
when one single phenotype is affected by more than one set of genes
allele
alternative forms of the same gene
wild type allele
the allele that occurs most frequently in a population
codominance & Ratio
Condition in which the phenotypic effect’s of a gene’s alleles are fully and simultaneously expressed in the heterozygote
1:2:1
Example of codominance with multiple allele
The ABO blood group characterized by an antigen called a glycoprotien found on the surface of red blood cells. Two forms of glycoprotein exist, A & B or none which is O Type. This makes three different allele for the same gene.
Can we study multiple alleles in an individual?
No, an individual diploid organism at at most 2 homologous gene loci that may be occupied by different alleles of the same gene. So, in humans, you must study multiple alleles thru the population
example of late onset
Huntington’s Disease
incomplete dominance & ratio
Expressing a heterozygous phenotype that is distinct from the phenotype of either homozygous parent. Also called partial dominance
1:2:1
Recessive Lethal Allele & Ratio
Mutations resulting i the synthesis of a gene product that is nonfunctional that can often be tolerated in the heterozygous state, but that in the homozygous recessive state, individuals will not survive. Time of death depends on when the product is essential.
It is often dominant with respect to phenotype and has a distinctive mutant phenotype.
2:1
Example of recessive lethal allele
The dwarf allele is dominant for causing dwarfism, so we used a capital letter D for that allele. However it is also recessive lethal (a different phenotype), so DD dies before birth, leaving 2 Dd (dwarf):1 dd (normal).
Dominant lethal allele
the presence f just one copy of the allele results in the death of the individual.
Example of dominant lethal allele
Huntington’s disease, due to dominant autosomal allele H ,where the onset of the disease in heterozygotes (Hh) is delayed into adulthood. Affected individuals undergo gradual nervous and motor degeneration until they die. This is a lethal disorder that has late onset and causes death at about age 40.
why do dominant lethal alleles not occur frequently in the population?
The affected individuals must reproduce before the lethal allele is expressed. Otherwise, all affected individuals die before being able to pass the train on to future generations.
epistasis & ratio
Occurs when the expression of one gene or gene pair masks or modifies the expression of another gene or gene pair.
9:3:4
complementation & ratio
2 genes but mutations in either have same ØT
9:7
