Topic 10.2: Inheritance Flashcards
Law of Independent Assortment
The inheritance of two different genes / traits will occur independently provided the genes are on separate chromosomes
Dihybrid Crosses
Determine allele combinations of offspring for two genes that are unlinked (on different chromosomes)
How to complete a dyhibrid cross
a) Designate characters to represent the alleles
b) Write down the genotype and phenotype of the parents
c) Write down all potential gamete combinations for both parents
d) Use a Punnett square to work out potential genotypes of offspring
e) Write out the phenotype ratios of potential offspring
Linkage group
Describes a group of genes whose loci are on the same chromosome
Linked genes and law of independent assortment
Linked genes will function as a single inheritable unit and will not follow the law of independent assortment
Crossing over and linked genes
a) Linked genes can be separated (unlinked) by crossing over
b) The novel allele combinations are called recombinants
Crossing over and loci
Recombinant phenotypes will only be evident if crossing over has occurred and thus occur at lower frequencies
Thomas Morgan and gene linkage
Morgan identified a number of different traits that did not conform to Mendelian ratios and surmised the following:
a) These traits represented linked genes (on same chromosome)
b) Linked genes can be uncoupled via recombination, but such events are uncommon (hence occur at low frequencies)
Types of variation in phenotypes
a) Monogenic traits
b) Polygenic traits
Monogenic traits
Tend to exhibit discrete variation, with individuals expressing one of a number of distinct phenotypes
Polygenic traits
Tend to exhibit continuous variation, with an individual’s phenotype existing somewhere along a continuous spectrum of potential phenotypes
Polygenic traits patterns
a) Increasing the number of loci responsible for a particular trait increases the number of possible phenotypes
b) A Gaussian (bell-shaped) normal distribution curve
