Introduction to Genetics
Chapter 11
ARE TRAITS INHERITED?
Gregor Mendel
• Used garden peas in his experiments
• Peas reproduce sexually in a process known as
fertilization
• Pea plants were true breeders – they
produced identical offspring if they were
allowed to self polinate
Gregor Mendel
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Studied 7 different pea plant traits
He crossed plants and studied their offspring
Original pea plant is the P generation
Offspring are the F1 generation
Offspring of crosses between parents with
different traits are called hybrids
Principle of dominance
• Some alleles are dominant and others are
recessive
Segregation
• Do recessive alleles disappear?
• F1 Cross
– P. 266
PROBABILITY & PUNNETT SQUARES
Genetics & Probability
• Likelihood that a particular even will occur =
probability
• Flipping a coin. What are the chances it will
land on heads? On tails?
• Alleles segregate completely random just like
flipping a coin
Punnett Squares
• Can be used to predict and compare the
genetic variations that will result from a cross
Punnett Squares
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Identical alleles for a particular trait = homozygous
Different alleles for a particular trait = heterozygous
Physical characteristics are called phenotypes
The actual alleles present for a trait or the genetic
make up is known as genotype