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Biology
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Quiz over 11.2 first Use the first few minutes to review
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Review 11.1/11.2
Review 11.1/11.2 Mendel’s Pea Plants How many traits did he observe? Initial Experiment – P/F1/F2 Law of Dominance Law of Segregation Punnett Square Monohybrid cross
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5. Mendel’s Experiment Generations
Parental (P) generation – true breeding parents F1 generation – the offspring of the Parental (P) generation F2 generation – the offspring of the F1 generation

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7. Law (Principle) of Dominance
Some alleles are dominant whereas others are recessive. Organism with a dominant allele for a particular trait will always have that trait expressed (seen) Shown by a capital letter Organism with a recessive allele for a particular trait will only be expressed when the dominant allele is not present Shown by a lowercase letter

8. Homozygous
Since organisms receive one gene for a chromosome pair from each parent, organisms can be heterozygous or homozygous for each trait. Homozygous (“homo” meaning same) – two identical alleles for a trait Alleles can either be homozygous dominant (TT) or homozygous recessive (Tt) Ex: TT, tt, PP, pp, etc

9. Heterozygous
Heterozygous (“hetero” meaning different) – two different alleles for a trait. One is dominant, the other recessive. Ex: Tt, Pp

10. Genotype
Genotype (Genetic Makeup) – reveals the type of alleles that an organisms has TT represents a homozygous dominant genotype. Therefore, what does tt and Tt represent?

11. Phenotype
Phenotype (Physical Characteristics) – is a description of the way that a trait is expressed, for example (B) is the allele for black hair and (b) is the allele for brown hair. Therefore, what would my phenotype be if my genotype was BB, Bb, or bb?

13. Review!
Carmen has brown eyes, would this be her genotype or phenotype?
Nolan has blonde hair, would this be his genotype or phenotype?
The genotype for tall flowers is TT, would the flower be homozygous dominant or homozygous recessive ? Why?
The genotype for a pea plant flower color that is homozygous recessive would be PP or pp?

14. Genotype = Genetic Makeup Phenotype = Physical Appearance
Remember ….
Genotype = Genetic Makeup
Phenotype = Physical Appearance
Homozygous = “Homo” = the same alleles
Heterozygous = “Hetero” = different alleles
Dominant = masks or dominates other allele; Capital Letter
Recessive = the allele that is masked unless present with another recessive allele; Lowercase letter

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The Law of Segregation
Alleles separate during gamete formation.
During gamete formation, alleles segregate from each other so that each gamete carries only a single copy of each gene. Each F1 plant produces two types of gametes—those with the allele for tallness and those with the allele for shortness. The alleles are paired up again when gametes fuse during fertilization. The TT and Tt allele combinations produce tall pea plants; tt is the only allele combination that produces a short pea plant.
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The Law of Segregation
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17. 11-3 Exploring Mendelian Genetics
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Mendel wondered if plant traits affected other plant traits… does the segregation of one pair of alleles affect the segregation of another pair of alleles? Example: Does plant height affect seed color? Must a round seed be yellow? This leads us to Mendel’s next round of experiments … you may have heard this before….
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19. Independent Assortment
What is the principle of independent assortment?
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20. Independent Assortment
To determine if the segregation of one pair of alleles affects the segregation of another pair of alleles, Mendel performed a two-factor cross.
Remember, Mendel’s term is “factor.” We say genes or alleles.
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21. Independent Assortment
The Two-Factor Cross: F1  
Mendel crossed true-breeding plants that produced round yellow peas (genotype RRYY) with true-breeding plants that produced wrinkled green peas (genotype rryy). (Let’s work out the problem together! – FOIL)
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22. Independent Assortment
The alleles for round (R) and yellow (Y) are dominant over the alleles for wrinkled (r) and green (y).
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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All of the F1 offspring produced round yellow peas (RrYy).
All 16 - phenotype: round yellow
All 16 - genotype: RrYy
Did this tell Mendel if green seed color was dependent on the wrinkled seed?
Did this show Mendel if alleles assort?
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24. Independent Assortment
The Two-Factor Cross: F2 
Mendel crossed the heterozygous F1 plants (RrYy) with each other to determine if the alleles would segregate from each other in the F2 generation.
F F1
RrYy × RrYy
Let’s work on it together! Remember to FOIL
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25. Independent Assortment
When Mendel crossed plants that were heterozygous dominant for round yellow peas, he found that the alleles segregated independently to produce the F2 generation.
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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26. Independent Assortment
In Mendel’s experiment, the F2 generation produced the following:
some seeds that were round and yellow (315)
some seeds that were wrinkled and green (32)
some seeds that were round and green (106)
some seeds that were wrinkled and yellow (103)
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27. Independent Assortment
The alleles for seed shape segregated independently of those for seed color. This principle is known as independent assortment.
Genes that segregate independently do not influence each other's inheritance.
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28. Independent Assortment
Mendel's experimental results were very close to the 9 : 3 : 3 : 1 ratio predicted by the Punnett square.
Mendel had discovered the principle of independent assortment.
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29. Independent Assortment
The principle of independent assortment states that genes for different traits can separate independently during the formation of gametes.
Independent assortment helps account for the many genetic variations observed in plants, animals, and other organisms.
Remember: genetic variation is so important in biology!
Independent Assortment
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30. A Summary of Mendel's Principles
Genes are passed from parents to their offspring. (inheritance)
If two or more forms (alleles) of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive. (principle of dominance)
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31. A Summary of Mendel's Principles
In most sexually reproducing organisms, each adult has two copies of each gene. These genes are segregated from each other when gametes are formed. (law of segregation)
The alleles for different genes usually segregate independently of one another. (independent assortment)
Know these!
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32. Beyond Dominant and Recessive Alleles
What inheritance patterns exist aside from simple dominance?
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33. Beyond Dominant and Recessive Alleles
Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.
Mendel was lucky he studied pea plants!
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34. Beyond Dominant and Recessive Alleles
Incomplete Dominance 
When one allele is not completely dominant over another it is called incomplete dominance.
In incomplete dominance, the heterozygous phenotype is between the two homozygous phenotypes.
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35. Beyond Dominant and Recessive AllelesRR
Incomplete Dominance
A cross between red (RR) and white (WW) four o’clock plants produces pink-colored flowers (RW). 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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36. Beyond Dominant and Recessive Alleles
Codominance 
In codominance, both alleles contribute to the phenotype.
In certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers.
Heterozygous 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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Red, white, roan cattle
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39. Beyond Dominant and Recessive Alleles
Multiple Alleles 
Genes that are controlled by more than two alleles are said to have multiple alleles.
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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40. 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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41. Human Blood Types – another example of multiple alleles
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42. Beyond Dominant and Recessive Alleles
Polygenic Traits  
Traits controlled by two or more genes are said to be polygenic traits.
Skin color in humans is a polygenic trait controlled by more than four different genes.
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44. Applying Mendel's Principles
Thomas Hunt Morgan used fruit flies to advance the study of genetics.
Morgan and others tested Mendel’s principles and learned that they applied to other organisms as well as plants.
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45. 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.
Chapter 13 and 14!!!! I’m so excited! You should be, too!
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46. Genetics and the Environment
Characteristics of any organism are determined by the interaction between genes and the environment.
In a way, genes provide a plan for development…how that plan unfolds depends on the environment.
For you, exercise and eat healthy!  It affects your genes and your jeans!
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11–3
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11–3
In a cross involving two pea plant traits, observation of a 9 : 3 : 3 : 1 ratio in the F2 generation is evidence for
the two traits being inherited together.
an outcome that depends on the sex of the parent plants.
the two traits being inherited independently of each other.
multiple genes being responsible for each trait.
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11–3
Traits controlled by two or more genes are called
multiple-allele traits.
polygenic traits.
codominant traits.
hybrid traits.
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11–3
In four o'clock flowers, the alleles for red flowers and white flowers show incomplete dominance. Heterozygous four o'clock plants have
pink flowers.
white flowers.
half white flowers and half red flowers.
red flowers.
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11–3
A white male horse and a tan female horse produce an offspring that has large areas of white coat and large areas of tan coat. This is an example of
incomplete dominance.
multiple alleles.
codominance.
a polygenic trait.
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11–3
Mendel's principles apply to
pea plants only.
fruit flies only.
all organisms.
only plants and animals.
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53. END OF SECTION