BIOL 112 Lecture Notes - Lecture 10: Punnett Square, Probability Theory, Wild Type
16 May 2018
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BIOL 112- Lecture 13- Mendelian Genetics
For a given character, offspring share traits
!!Character e.g. colour, stature, facial features etc.
!!Traits e.g. light or dark, short or tallo
!!Siblings will not have identical traits for a given character
Continuous variation – seemingly infinite number of traits for a given character that fall
along a continuous spectrum
"!E.g. height, skin, colour
Discrete variation – only two or a few traits for a given character
"!E.g. fur color in mice
"!Mendel focused on these; used peas because they show discrete variation
Definitions:
!!Gene – unit of heredity
!!Alleles – different forms of a gene
!!Wild type – the predominant allele, present in >99% in a population
!!Mutant allele – a change from the wild type allele, typically the result of a recent
mutation
o!Also, refer to alleles that cause disease
!!Polymorphic allele – an allele that is present in >1% of the population
!!Homozygous – having two of the same allele
!!Heterozygous – having one of each allele
!!Probability theory: the probability of two independent events is the product of
the probability of each event
o!Using probability theory (instead of Punnett squares) you can still calculate
the ratios of the traits of the pea plants
o!E.g. probability of flipping heads exactly twice out of four flips of a coin is
3/8
!!Genotype – the set of alleles an organism has
!!Phenotype – the set of traits an organism displays
!!Genotype determines phenotype
!!Phenotype may not uniquely determine genotype
o!Test cross can be done in order to determine genotype (heterozygous or
homozygous dominant)
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BIOL 112 Full Course Notes
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Document Summary
Character e. g. colour, stature, facial features etc. Traits e. g. light or dark, short or tall o. Siblings will not have identical traits for a given character. Continuous variation seemingly infinite number of traits for a given character that fall along a continuous spectrum. Discrete variation only two or a few traits for a given character. Mendel focused on these; used peas because they show discrete variation. Alleles different forms of a gene. Wild type the predominant allele, present in >99% in a population. Mutant allele a change from the wild type allele, typically the result of a recent mutation o also, refer to alleles that cause disease. Polymorphic allele an allele that is present in >1% of the population. Homozygous having two of the same allele. Heterozygous having one of each allele. Genotype the set of alleles an organism has. Phenotype the set of traits an organism displays.
