1. Independent Assortment
The Punnett square predicts a 9 : 3 : 3 :1 ratio in the F2 generation.
When Mendel crossed plants that were heterozygous dominant for round yellow peas, he found that the alleles segregated independently to produce the F2 generation.
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2. Independent Assortment
In Mendel’s experiment, the ___ generation produced the following:
some seeds that were round and yellow
some seeds that were wrinkled and green
some seeds that were round and green
some seeds that were wrinkled and yellow
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3. Independent Assortment
The alleles for seed shape _________________ _______________ of those for seed color. This principle is known as independent assortment.
Genes that segregate independently do not influence each other's _______________.
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4. Independent Assortment
Mendel's experimental results were very close to the _______________ ratio predicted by the Punnett square.
Mendel had discovered the principle of _______________ ________________.
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5. Independent Assortment
The principle of independent assortment states that genes for different traits can ________________ ____________________ during the formation of gametes.
Independent assortment helps account for the many genetic variations observed in plants, animals, and other organisms.
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6. A Summary of Mendel's Principles
Genes are passed from parents to their offspring.
If two or more forms (_______________) of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive.
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7. A Summary of Mendel's Principles
In most ____________________ reproducing organisms, each adult has two copies of each gene. These genes are segregated from each other when gametes are formed.
The ______________ for different genes usually segregate independently of one another.
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8. Beyond Dominant and Recessive Alleles
What inheritance patterns exist aside from simple dominance?
Some alleles are neither _____________ nor ______________, and many traits are controlled by multiple alleles or multiple genes.
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9. Beyond Dominant and Recessive Alleles
Incomplete Dominance 
When one allele is not completely dominant over another it is called __________________ ______________.
In incomplete dominance, the heterozygous phenotype is between the two homozygous phenotypes.
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10. Beyond Dominant and Recessive AllelesRR
A cross between red (_____) and white (_____) four o’clock plants produces pink-colored flowers (_____). WW
Some alleles are neither dominant nor recessive. In four o’clock plants, for example, the alleles for red and white flowers show incomplete dominance. Heterozygous (RW) plants have pink flowers—a mix of red and white coloring.
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11. Beyond Dominant and Recessive Alleles
Codominance 
In ______________________, both alleles contribute to the phenotype.
In certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers.
_____________________ chickens are speckled with both black and white feathers. The black and white colors do not blend to form a new color, but appear separately.
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12. Beyond Dominant and Recessive Alleles
Multiple Alleles 
Genes that are controlled by more than two alleles are said to have _______________ ___________________.
An individual can’t have more than two alleles. However, more than two possible alleles can exist in a population.
A rabbit's coat color is determined by a single gene that has at least four different alleles.
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13. Beyond Dominant and Recessive Alleles
Different combinations of alleles result in the colors shown here.
KEY
C = full color; dominant
to all other alleles
cch = chinchilla; partial defect in pigmentation; dominant to ch and c alleles
ch = Himalayan; color in certain parts of the
body; dominant to
c allele
c = albino; no color;
recessive to all other
alleles
Coat color in rabbits is determined by a single gene that has at least four different alleles. Different combinations of alleles result in the four colors you see here. photo credits: 1. ©John Gerlach/Visuals Unlimited 2.Animals Animals/©Richard Kolar 3. ©Jane Burton/Bruce Coleman, Inc. 4. ©Hans Reinhard/Bruce Coleman, Inc.
AIbino: cc
Chinchilla: cchch, cchcch, or cchc
Himalayan: chc, or chch
Full color: CC, Ccch, Cch, or Cc
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14. Beyond Dominant and Recessive Alleles
Polygenic Traits  
Traits controlled by two or more genes are said to be _________________ ________________.
Skin color in humans is a polygenic trait controlled by more than four different genes.
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15. Applying Mendel's Principles
Mendel’s principles can be used to study inheritance of human traits and to calculate the probability of certain traits appearing in the next generation.
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16. Genetics and the Environment
Characteristics of any organism are determined by the interaction between genes and the environment.
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17. The _____ of _____________
Mendelian principle explaining that b/c each plant has two different alleles, it can produce two different types of gametes.
During fertilization, male and female gametes randomly pair to produce four combinations of alleles 17

18. 18

19. 19

20. Law of __________ ____________
Mendelian principle stating that genes for different traits are inherited independently of each other 20

21. 21

22. 22

23. Wrap-Up
Mendel deduced that for each characteristic, an organism inherits ___ genes, one from each parent.
When the __ alleles differ, the dominant allele is expressed and the recessive allele remains hidden.
___ genes or alleles separate (__________) during gamete production in meiosis, resulting in the sorting of alleles into separate gametes (the law of segregation). 23

24. 3c*. Know how to predict the probable mode of inheritance from a pedigree diagram showing phenotypes. 24

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Human Chromosomes
Human Chromosomes
Cell biologists analyze chromosomes by looking at karyotypes.
Cells are photographed during mitosis. Scientists then cut out the chromosomes from the photographs and group them together in pairs.
A picture of chromosomes arranged in this way is known as a _____________________.
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26. Copyright Pearson Prentice Hall
Human Chromosomes
Human Karyotype
These human chromosomes have been cut out of a photograph and arranged to form a karyotype. Photo credit: ©CNRI/Science Photo Library/Photo Researchers, Inc.
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Human Traits
Pedigree Charts 
A ________________ chart shows the relationships within a family.
Genetic counselors analyze pedigree charts to infer the genotypes of family members.
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Human Traits
A circle represents
a female.
A square represents
a male.
A vertical line and a bracket connect the parents to their children.
A horizontal line connecting a male and a female represents a marriage.
A circle or square that is not shaded indicates that a person does not express the trait.
A shaded circle or square indicates that a person expresses the trait.
This drawing shows what the symbols in a pedigree represent.
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