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Genetics
What is Genetics
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Genetics is the scientific study of
heredity.
Heredity is what makes each
species unique.
History
Gregor Mendel
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Austrian Monk
Famous for his work with pea plants
He is known as the father of
genetics
Mendel
Mendel’s Work
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Mendel used true-breeding plants which
means if they were left to breed with
themselves they would produce offspring
identical to themselves.
Mendel studied 7 different traits in pea
plants.
A trait is a specific characteristic that
varies from one individual to another.
More on Mendel’s Work
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Hybrids are offspring from parents
with different traits.
Genes are the chemical factors that
determine a trait.
The different forms of a gene are
called alleles.
The Principle of Dominance
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The principle of dominance states
that some alleles are dominant and
others are recessive.
Dominant alleles are always
expressed.
Recessive alleles are only expressed
if both alleles are recessive.
Segregation & Independent Assortment
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The separation of alleles during
meiosis to form gamates (sex cells).
The Law of Independent Assortment
states that genes for different traits
can segregate independently during
the formation of gamates.
Laws of Inheritance
Probability & Genetics
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Probability is the likelihood that an
event will happen.
The principle of probability can be
used to predict the outcomes of
genetic crosses.
Probability
Punnett Squares
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Diagram used to predict genetic
crosses.
Individuals with identical alleles are
called homozygous
Individuals with different alleles are
called heterozygous
Phenotype – physical characteristic
Genotype – genetic makeup
How to use Punnett Squares
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Choose a letter to represent the
alleles in the cross.
Write the genotypes of the parents.
Determine the possible gametes
(reproductive cells) that the parent
can produce.
Enter the possible gamete at the top
and side of the Punnett square.
More Punnett Squares
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Complete the Punnett square by
writing the alleles from the gametes in
the appropriate boxes.
Determine the phenotypes of the
offspring.
Using the results of step E and F write
down the genotypic and phenotypic
ratios.
Naked Punnett Square
Punnett Squares Monohybrid &
Dihybrid Crosses
Punnett Squares
Mendel’s Principles
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The inheritance of biological
characteristics are determined by genes.
For two or more forms of a gene,
dominance and recessive forms may
exist.
Most sexually reproductive organisms
have two sets of genes that separate
during gamete formation.
Alleles segregate independently.
Beyond Dominant and Recessive
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Incomplete Dominance – One allele is not
completely dominant over the other.
White flower crosses with a red = pink
flower.
Codominance – Both alleles contribute to
the phenotype. Red cow X White Cow =
Roan Cow.
Multiple Alleles – More than two alleles
control the phenotype. Coat color of
rabbits.
Polygenic traits – Several genes control
the trait. Skin color in humans.
Examples