Mendelian Inheritance II Flashcards
What did Mendel discover by following more than one characteristic ( a dihybrid cross) that he did not with his monohybrid crosses?
The law of independent assortment.
When would the law of independent assortment not appy?
This law applies only to genes on different chromosomes. Genes located near each other on the same chromosome tend to be inherited together.
What is the result of a cross between two true-breeding parents differing in two characters?
This cross produces dihybrids in the F1 generation which are heterozygous for both characters.
What can determine whether two characters are transmitted to offspring as a package or independently?
A dihybrid cross between F1 dihybrids.
What is the multiplication rule of probability?
This rule states that the probability that two or more independent events will occur together is the product of their individual probabilities.
What is the addition rule of probability?
This rule states that the probability that any one of two or more mutually exclusive events will occur is calculated by adding together their individual probabilities.
What are the three ways the inheritance of characters by a single gene may deviate from simple Mendelian patterns?
- When phenotypes of alleles are not completely dominant or recessive
- When a gene has more than two alleles
- When a gene produces multiple phenotypes
What is incomplete dominance?
The idea that the phenotype of F1 hybrids is an intermediate of its parental varieties.
How does the M and S antigen system exhibit codominance?
The two alleles on chromosome 4 designate LM and LN. The blood type is due to a glycoprotein present on the surface of red blood cells which behaves as a native antigen. An individual can exhibit either one or both antigenic substances (LM and LN)
How are phenotypes determined in a codominant system?
The phenotype of the heterozygote is the sum of the phenotypes of the two homozygotes.
What determines the four phenotypes of the ABO blood group in humans?
Three alleles for the enzyme (i) that attaches A or B carbohydrates to red blood cells: IA, IB, and i.
What happens in epistasis?
A gene at one locus alters the phenotypic expression of a gene at a second locus.
What happens in polygenic inheritance?
Multiple genes independently affect a single trait.
What are quantitative characters?
Those that vary in the population along a continuum.
What is polygenic inheritance, and what usually indicates it?
Quantitative variation usually indicates polygenic inheritance, an additive effect of two or more genes on a single phenotype.
