Exam 2 - Chapter 8: Variation of Phenotypes Flashcards
What is a dihybrid cross? What is the genotypic ration produced?
When two individuals with two heterozygous traits reproduce; 9:3:3:1
What is Mendel’s law of independent assortment?
Pairs of chromosomes segregate independently during meiosis
What is a complex trait?
A phenotype controlled by multiple genes and/or the environment
What is a fully dominant allele?
When an individual expresses dominant trait and no degree of recessive trait if they have a dominant allele
What is incomplete/intermediate dominance?
A heterozygous individual experiences an intermediate of phenotypes
What is codominance?
A heterozygous individual expresses both alleles equally
What is the ABO locus?
A gene of chromosome 9 that makes glycosyl transferase which modifies H-antigens on red blood cells
How do alleles A and B of the ABO locus compare in dominance?
They are codominant
What is an allele series?
dominance varies between alleles in a gradient
What is pleiotropy?
one gene produced multiple effects in an organism
How do mutations differ from alleles?
Associated with disease, immediate and low frequency
What is a polymorphism?
difference in a specific part of the genome in a species; gene with at least two alleles
What is a recessive lethal allele?
A recessive allele that codes for a lethal trait
What phenotypic ratio are offspring of heterozygous individuals with lethal alleles represented in?
thirds
What is dominant recessive allele?
An dominant allele that is lethal when homozygous
What is consanguinity and a consequence?
Mating with a close relative; increase chance of homozygous lethal genotype
What is epistasis?
Expression of a gene in influenced by expression of another
When does a 15:1 ratio result?
Epistasis; presence of a dominant allele in either one of two genes causes expression of one phenotype
How does a 9:3:3:1 ration or 9:4:3 ration result in epistastis?
homozygous recessive for one of two genes masks the dominant trait
What are complementary genes?
Both genes require a specific allele for phenotype to occur
How does 9:7 phenotypic ratio arise?
If one of the genes in homozygous, one trait occurs; Both genes require dominant allele to have other trait
What is a polygenic trait?
When one trait is influenced by multiple genes
What is penetrance?
Whether or not a phenotype persists despite individual having the genotype
What is polydactyly?
Having more fingers than normal
