Transcript Ch. 11: “Introduction to Genetics”

Ch. 11: “Introduction to
Genetics”
11.1: The Work of Gregor Mendel” &
11.2: “Probability and Punnett Squares”
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Gregor Mendel’s Peas
• Gregor Mendel was an Austrian monk
who was born in 1822.
• After becoming a priest, he spent
several years studying science and
math.
• Mendel worked in the monastery and
taught at a high school.
• He was also in charge of the monastery
garden.
• It was in this garden that Mendel’s
experiments with pea plants laid the
foundations of the science of genetics.
• Mendel had true breeding plants,
meaning that if they were allowed to
self-pollinate, they would produce
offspring identical to themselves.
2
Genes and Dominance
• Mendel studied 7 different pea plant
traits.
• A trait is a specific characteristic.
• Mendel crossed plants with each of
the 7 contrasting characteristics
and studied their offspring.
• P (parent), F1 (first offspring)
• From his crosses, Mendel
concluded that biological
inheritance is determined by factors
that are passed from one
generation to the next.
• Mendel’s 2nd conclusion is called
the principle of dominance. Some
alleles are dominant and others are
recessive.
3
Punnett Squares
• The gene combination that might
result from a genetic cross can be
determined by drawing a diagram
known as a Punnett square.
• Punnett squares can be used to
predict and compare the genetic
variations that will result from a cross.
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Homozygous Dominant: TT
Homozygous Recessive: tt
Heterozygous: Tt
Phenotype: physical characteristics
Genotypes: genetic makeup
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