Name: _____________________________
Heredity Part 1: Genetics
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_____________________
o 1800’s Austrian monk, mathematician, and scientist
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Began working in the garden at his monastery
o _______________________
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His work led to an understanding of how traits are passed from ____________________
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The passing of traits from parents to offspring is called __________________
o Primarily worked with a variety of garden peas
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Noticed several traits that appeared to follow certain patterns of inheritance
o Mendel’s Observations
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Mendel mated pea plants together until he got plants that were ___________________
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Also known as pure-bred
o These are organisms that always pass on ____________________
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Ex. _______ plant that always has _________ offspring
Once he established 2 true-breeding lines for each trait, he mated them together
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For example, true-breeding yellow seed and true breeding green seeds
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He noticed that all of the offspring looked like _____ of the parents, but not the
other (Ex. All ________, no _________)
o Called them ____________ because they got one gene from each parent
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He then ________________ each of the offspring
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He noticed that most looked like the parent, but some did not
o Generations in crosses:
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P=_______________________
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F1=_______________________
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First ones to be crossed
Filial=children
F2=________________________
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Grandchildren
o Mendel’s Hypotheses
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He hypothesized that one of the traits was ____________________ the other
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He called these traits ________________
Because the other trait was not expressed in the first generation, but reappeared in the
second, he hypothesized that the trait was still there, but was being ________________
by the dominant trait.

He called these traits ________________
o Example of Mendel’s Experiment-Yellow and green seeds
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Mendel developed a true-breeding line of plants with ________ seeds and a truebreeding line of plants with ______ seeds
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He took one __________-seeded plant and one __________-seeded plant and mated
them together
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He then took each of these _________ -seeded plants and self-pollinated them
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All of the offspring had _________ seeds
______ of the offspring had yellow seeds and ______ had green seeds
He concluded that yellow was ________________ and green was _________________
o Results of Mendel’s Experiment
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Mendel’s experiments continually showed that ____ of the plants showed the dominant
trait and ____ showed the recessive trait
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__:__ ratio
o Mendel’s Laws of Inheritance
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Law of _______________
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For any particular trait, the pair of ____________ from each parent separate and
only ____ allele passes from each parent to an offspring
o Recall that we have ___________ of chromosomes (one set from mom
and one set from dad)
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During meiosis, ___ of these are sorted into each gamete (sex cell)
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Which one winds up in each is ___________
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Law of __________________________
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Different pairs of alleles for one trait are passed to offspring _____________ of
alleles for other traits
o Most traits are NOT linked in any way. You could get your mom’s blue
eyes without getting her blonde hair, height, etc.
o Mendel’s Principle of Dominance
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Traits can be ____________ or _____________
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Dominant alleles mask, or ______________, recessive alleles
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Recessive alleles can only be expressed if the offspring receives _____ of the
recessive alleles
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Any time a dominant allele is present, it will be _______________
Symbols for alleles
o Dominant alleles are represented by _________________________
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Example: A, B, C, D
o Recessive alleles are represented by _________________________
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Example: a, b, c, d
o The gene is represented by _________________ letter, and dominant and recessive alleles of
the gene are shown by whether they are _______________________
o You Try It: Indicate whether the following are dominant or recessive:
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T-
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d-
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P-
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E-
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e-
Homozygous vs Heterozygous
o Recall that organisms get 2 alleles-1 from each parent
o _______________-2 of the same alleles for a trait
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“Homo” means _________
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Example: ___ or ____
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Can be homozygous dominant (_____) or homozygous recessive (____)
o _______________-2 different alleles for a trait
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“Hetero” means _____________
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Example: ____ or tT
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Note: The latter is rarely used, but will sometimes be the result in a Punnett
Square
o You Try It: Indicate whether the following are heterozygous, homozygous dominant, or
homozygous recessive
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TT-
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Tt-
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tT-
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tt-
Punnett Squares
o Tool to __________________ of a cross (mating)
o Often a 2x2 grid
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Can be larger if including more traits
o Couple of different types
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____________ cross (one trait)
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____________ cross (2 traits)
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Trihybrid cross (3 traits)-gets too time consuming for this class
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And more that are too complicated to be done by hand and are instead done using
computers
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Punnett Squares Show Probability
o Not actuality!
o Coin flip
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If you flip a coin, what is the chance that it comes up heads? _________
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If you flip it again, what is the chance that it comes up heads a second time? _____
o If there is a 1 in 4 chance that offspring will have blue eyes, and you have 3 children with brown
eyes, will the 4th one for certain have blue eyes? __________
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Using Punnett Squares
Draw example one here:
o Begin by drawing a 2x2 grid
o Place one parent’s alleles on top
o Place the other parents alleles on the left side
o Bring ones on the top down
o Bring ones on the left across
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Practice Problem
o A pea plant with genotype Rr is mated with a pea plant with genotype rr. What genotypes could
the offspring have?
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Genotype and Phenotype
o Genotype- The genes (__________) that an organism has
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Geno=gene
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Example: Aa, BB, cc
o Phenotype- The expression (_______________) of the genotype
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Ph-Physical
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Example: Green eyes, brown hair, tall
o You Try It: Indicate whether the following are genotypes or phenotypes.
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Aa-
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Blue eyes-
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Rolling tongue-
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TT-
Principles of heredity
o Traits are controlled by ___________ (different versions of a gene) on a chromosome
o An allele can be ________________ or _______________________
o When a pair of chromosomes separate during meiosis, the different alleles for a trait move into
different _____________________
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Dihybrid Crosses
o Deals with 2 traits
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Looking at 2 genes, so ____ possible alleles
o Little bit more complicated
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Punnett Square will be ________
o ____ possible combinations
o _______________________ is still followed
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F1 generation will still show ____________ phenotype
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F2 generation will have a ration of ___________________
o How to set up Punnett Square
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One allele from each trait will join with one for the other trait, and will give 4 allele
combinations
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Ex: AaBb  ___________________________
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Do for both parents
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Draw a 4x4 grid
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Place alleles for one parent on top, the other on the side
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Solve like other Punnett Squares, only make sure to bring both alleles down and across
o Example Dihybrid Cross

If you cross a pea plant with genotype Rryy and one with rrYY, what are the possible
genotypes of the offspring?
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1st plant allele combinations: _______________________________________
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2nd plant allele combinations: _______________________________________

Draw a 4x4 grid and place alleles: