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Mendel and
Meiosis
Gregor Mendel HeredityHeredity is the passing of
characteristics from parents to offspring.
GeneticsGenetics is the study of heredity or how those traits are inherited.
Gregor Mendel was the first person to succeed in predicting how traits were inherited thus he became known as the Father of Genetics.Father of Genetics.
Gregor Mendel Gregor Mendel is best known for his
study of pea plantspea plants. He used pea plants because they
have 2 distinct sex cells called gametesgametes.
Mendel pollinated the flowers himself by transferring the male pollen to the stigmastigma of the flower (pollination).(pollination).
Pollen
Uniting of the male and female gametes is called fertilizationfertilization.
Mendel cross-pollinatedcross-pollinated pea plants in order to study the various traits:
DominaDominantnt: the trait that was
observed
RecessiveRecessive: the trait
that disappear
ed.
Crossing traits PurebredPurebred: a cross between plants with
identical traits. HybridHybrid: a cross between plants with different
traits like tall and short. Mendel’s first cross he called a monohybridmonohybrid
cross. (Mono means one) Later Mendel began crossing plants with 2
traits. These crossed were called dihybriddihybrid crosses.
Testcross: Breeding an individual of unknown genotype to a homozygous recessivehomozygous recessive individual to reveal the unknown genotype
Parent generat
ion
Filial (son or
daughter) generation
2nd Filial
generation
Grandchildren
Children
Parents
Genotypes and Phenotypes?? PhenotypePhenotype – the way that the
organism lookslooks and behaves.PhenoPheno (physical) (physical) typetype (model) (model)
Genotypesenotypes – the combination of genesgenes in the organism.
GenGen (birth) (birth) typetype (model) (model)
Genotypes and Phenotypes
PhenotypePhenotype
GenotypeGenotype
Genotypes and Phenotypes Homozygous dominant:
Homo (same)
Homozygous recessive:
Heterozyous: Hetero (different)
Mendel’s Laws of Inheritance Law of segregation:Law of segregation: the 2 genes
for each trait will segregatesegregate during the formation of the gametesgametes.
Mendel’s Laws of Inheritance Law of independent assortment: Law of independent assortment:
Each trait (or gene) is inherited Each trait (or gene) is inherited independently of the other independently of the other traitstraits.
In other words, all blondes do not have blue eyes.
Punnet Squares In 1905, Reginal PunnetPunnet, an
English biologist, devised a shorthand way of predicting the outcomes of the various crosses.
These are called Punnet squares.
Monohybrid crosses
Genotypes
Phenotypes
BB: 1…25%Bb: 2…50%bb: 1…25%
White: 3…75%(BB and Bb)black: 1…25%
BB: White
bb: Black
Dihybrid crosses