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Chapter 12; Section 2
Mendel’s Theory
Key Ideas
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What patterns of heredity were explained by
Mendel’s hypotheses?
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What is the law of segregation?
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How does genotype relate to phenotype?
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What is the law of independent assortment?
Explaining Mendel’s Results
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Mendel hypotheses are collectively called the
Mendelian _________ of ________
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explains _____ patterns of ______. In these patterns, two
of several _______ of a gene combine and result in one of
several possible ________.
__________ traits result from different ________
of genes. _______ version of a _________ is called
an ________.
Explaining Mendel’s Results
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Each ________can ____to a _______ trait.
_____ can come ____ either ________
because each ________ of _______ is
_____________ when _________ form
during __________.
______ one of the _____ is _______ on to
_________.
Alleles
Explaining Mendel’s Results
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An ________ that is fully ____________
whenever it is ______ is called __________.
An ______ that is not ________ when a
________ allele is ______ is called ______.
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A _______ allele is ________ only when there is
____ dominant allele ____________.
__________ may also be called _________
or ____________.
Random Segregation of Alleles
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_______ pairs ____
_______ during _____
 ______ decides which
_____ from each
parent will be ______
on.
the law of ________
holds that when an
organism ________
gametes, _____ pair of
_______ is ________
and each ______ has an
_____ chance of
_________ either one
of the _________.
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Mendel’s Findings in Modern Terms
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________represent the function of alleles.
________ allele is shown as a _______ letter.
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_____ allele is shown as a ________ letter
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Polydactyly is dominant
D represents the presence of the dominant allele
Normal number of fingers & toes is recessive
d represents the recessive allele
Offspring _______
show a _____ for
____ allele that
they _________.
Instead, __________
of alleles determine
traits. (ex. Dd, dd or DD)
•Dd or DD
•dd
Mendel’s Findings in Modern Terms
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The set of _______ ___________ of alleles
that an ______ has for a character is called
the ___________.
The __________ trait that _________
from the genotype’s set of alleles is called
the __________.
Thus, ________ determines ____________.
Mendel’s Findings in Modern Terms

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If an individual has two ________ alleles of a
______ gene, the individual is _______ for
the related character.
(ex. dd or DD)
If an individual has two ________ alleles of a
______gene, the individual is _________ for
the related character.
(ex. Dd)
Mendel’s Second Experiments
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A ______-cross involves two ________, such
as seed color and seed shape.
Mendel used dihybrid crosses in his second
experiments and found that the _______ of
one _________ did ____ affect the
_________ of another character.
In modern terms, the law of _________
________holds that during _______
formation, the _______ of each gene
segregate ____________.
Dihybrid Crosses
Mendel’s Second Experiments
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Genes are said to be _____ when they are_____
together on ____________.
Scientists now know that many genes are ______ to
each other as parts of chromosomes.
______that are _________ close together on the
same chromosome will ____ separate __________.
The only genes that follow Mendel’s law of
independent assortment are those that are far apart.
Summary
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Mendelian theory explains simple patterns of
inheritance. In these patterns, two of several
versions of a gene combine and result in one of
several possible traits.
In modern terms, the law of segregation holds that
when an organism produces gametes, each pair of
alleles is separated and each gamete has an equal
chance of receiving either one of the alleles.
Genotype determines phenotype.
In modern terms, the law of independent assortment
holds that during gamete formation, the alleles of
each gene segregate independently.