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Trait
Specific feature/characteristic
e.g. Height, lactose intolerance, attached earlobes, hair texture
Blending theory
developed in the 1800s that believed characteristics of parents were blended and presented in the offspring
Why were pea plants chosen?
Self fertilizing plants
1 plant contains both male and female gametes = control which parent produces offspring
Distinct qualitative traits w 2 distinguishable forms for easy observation. e.g. round or wrinkly seeds
Pea plants are true breeding plants = offspring still exhibit the same traits after generations
e.g. plant w purple flowers = offspring ALWAYS w purple flowers
What were the 3 conclusions that Mendel made from the experiments?
blending theory was incorrect, if it was correct the flower colour should’ve been light purple (white x purple)
Law of segregation: offspring inherit ONE allele from each parent
Principle of dominance
What is the law of segregation?
Law of segregation = during meiosis, gametes will only receive one of the 2 alleles for each gene
Pea plant flower colour gene: Purple allele & white
Offspring inherit 1/ 2 alleles from each parent bc chromosomes segregate randomly during gamete formation
which sperm fertilizes which egg = random
What is the principle of dominance?
traits are determined by the pair of alleles
There are dominant & recessive alleles
IF the pair is: DOM + REC → only the dom trait will be expressed
rec allele never expressed when dom allele is present
Homozygous
inherited same version of alleles from each parent
e.g. BB or bb
Heterozygous
inherited different version of alleles from each parent
e.g. Bb or bB
Genotype
allele combination for any trait found in an organism
Bb x BB
Phenotype
an individual’s observable traits
e.g. height , eye colour, blood type
Notation: Dom & Rec alleles
alleles are rep. by letters
Dom: CAPITALS → BB
rec: lower case → bb
Punnett square
dom alleles are listed first
