Essential Questions:

1. Georgia Standards:1.Explain the relationship between changes in DNA and the appearance of new traits. 2. Explain the relationship between changes in DNA and the appearance of new traits. Essential Questions: How do you predict the probability of various genotypes inherited and the expressed phenotypes? How does meiosis generate variation in offspring?

2. Genetics is the scientific study of heredity. Gregor Mendel (1860’s) an Austrian Monk, was interested in figuring out how heredity was determined in plants and animals. used pea plants quantitative approach to collect data. Mendel studied seven different pea plant traits. Seed shape & color, pod shape & color, flower height & position and seed coat color A trait is a specific characteristic, such as seed color or plant height, that varies from one individual to another. Gregor Mendel: Father of Genetics

4. Gregor Mendel’s Experiment: • Mendel crossed plants with each of the seven contrasting traits and studied their offspring. • Mendel called each original pair of plants the P (parental) generation. • These peas were true-breeding (self-pollination), meaning that if they were allowed to self-pollinate, they would produce offspring identical to themselves.

5. He called the offspring of the P-generation, the F1, or “first filial,” generation. Filius is the Latin word for “son.” These pea plants were cross pollinated. In cross-pollination, male sex cells in pollen from the flower on one plant fertilize the egg cells of a flower on another plant. The offspring of crosses between parents with different traits are called hybrids. The F2 generation was allowed to self-pollinate Out of 929 F2 Generation plants, 705 were purple and 224 were white. Ration of 3 purple to 1 white Gregor Mendel’s Experiment:

6. How do we find the results of a genetic cross? • The principles of probability can be used to predict the outcomes of genetic crosses. • The gene combinations that might result from a genetic cross can be determined by drawing a diagram known as a Punnett square. (See note sheet)

7. Gregor Mendel’s Conclusions: • Genes and Dominance • Mendel’s first conclusion was that biological inheritance is determined by factors (genes) that are passed from one generation to the next. • Each of the traits Mendel studied was controlled by one gene that occurred in two contrasting forms. • The different forms of a gene are called alleles

8. Punnett Squares • Organisms that have two identical alleles for a particular trait—TT or tt in this example—are said to be homozygous • Organisms that have two different alleles for the same trait are heterozygous (Ex: Tt) • Homozygous organisms are true-breeding for a particular trait. Heterozygous organisms are hybrid for a particular trait.

9. Punnett Squares • All of the tall plants have the same phenotype, or physical characteristics. • They do not, however, have the same genotype, or genetic makeup.

10. Gregor Mendel’s Conclusions: • Mendel’s second conclusion is called the principle of dominance, which states that some alleles are dominant and others are recessive. • Alleles that are expressed are considered DOMINANT. • An organism with a dominant allele for a particular form of a trait will always have that form. • Alleles that are present in the genotype, but not expressed in the phenotype are considered RECESSIVE. • An organism with a recessive allele for a particular form of a trait will have that form only when the dominant allele for the trait is not present.

11. Gregor Mendel’s Conclusions: • Segregation of Alleles: • When each F1 plant flowers, the two alleles are segregated from each other so that each gamete carries only a single copy of each gene. • Therefore, each F1 plant produces two types of gametes—those with the allele for tallness and those with the allele for shortness.

12. During gamete formation, alleles are segregated from each other so that each gamete carries only a single copy of each allele. 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. Law of Segregation:

13. (Law ofIndependent Assortment) Genes for different traits can segregate independently during the formation of gametes. Did this mean that the two dominant alleles would always stay together?

14. Principle of dominance • Some alleles are dominant and others are recessive. • The importance of Mendel’s work on heredity was not discovered until 30 years later. • Scientist soon realized that CHROMOSOMES are the carriers of heredity.

15. Genes determine inheritance of biological characteristics. Genes are passed from parents to offspring Some forms of the gene may be dominant and others may be recessive. In most sexually reproducing organisms, each adult has two copies of each gene—one from each parent. These genes are segregated from each during gamete formation. The alleles for different genes are assorted independently of one another. A Summary of Mendel’s Principles

16. Pop Quiz: Use Book- Chp. 10.2 • What are dominant and recessive alleles? • What happens to alleles during segregation? 3. What did Mendel conclude determines biological inheritance? 4. Describe how Mendel cross-pollinated pea plants. 5. Describe how Mendel self-pollinated pea plants. 6. Give an example of the law of independent assortment.

17. Probability and Punnett Squares • The principles of probability can be used to predict the outcomes of genetic crosses. • The gene combinations that might result from a genetic cross can be determined by drawing a diagram known as a Punnett square. (See note sheet)

18. This Punnett square shows the probability of each possible outcome of a cross between hybrid tall (Tt) pea plants. Genotype: 25% TT, 50% Tt, 25%tt (1:2:1) Phenotype: 75% Tall, 25% short (3:1) Punnett square

19. Dihybrid Cross: Shows inheritences of two traits at once F1 Mendel crossed plants that were homozygous dominant for round yellow peas with plants that were homozygous recessive for wrinkled green peas. All of the F1 offspring were heterozygous dominant for round yellow peas. The cross did not indicate whether genes assort, or segregate, independently. A Dihybrid Cross: F1

20. A combination of alleles were produced that were not found in either parent This means that genes for different traits can segregate independently during the formation of gametes. (Independent Assortment) Did this mean that the two dominant alleles would always stay together? Or would they “segregate independently.”

21. Dihybrid Cross Problem • Determine the genotype and phenotype ratios and percents for a F2 generation dihybrid cross of two plants; one that is homozygous recessive for short, purple leaves and the other that is homozygous dominant for tall, orange leaves. • Height (H-tall, h-short) • Color (C-orange, c-purple)

22. Alleles are separated during gamete formation “Factors” determine traits Some alleles are dominant, and some alleles are recessive Law of Dominance Law of Segregation Concept Map Gregor Mendel experimented with concluded that Pea plants genes for different traits can segregate independently during the formation of gametes which is called the which is called the Law of Independent Assortment which is called the Go to Section:

23. Exceptions to Simple Dominance • Does the segregation of one pair of alleles affect the segregation of another pair of alleles? • For example, does the gene that determines whether a seed is round or wrinkled in shape have anything to do with the gene for seed color? Must a round seed also be yellow?

24. Exceptions to the Laws: • Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes. • incomplete dominance occurs when one allele is not completely dominant over another • In incomplete dominance, the heterozygous phenotype is somewhere in between the two homozygous phenotypes.

25. 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 Incomplete Dominance 

26. Incomplete Dominance Practice • In Mendel's experiments, if the gene for tall (T) plants was incompletely dominant over the gene for short (t) plants, what would be the result of crossing two Tt plants? • A. 1/4 would be tall; 1/2 intermediate height; 1/4 short • B. All the offspring would be tall. • C. 1/2 would be tall; 1/4 intermediate height; 1/4 short. • D. All the offspring would be intermediate. • E. 1/4 would be tall; 1/4 intermediate height; 1/2 short.

27. Disappearance of parental phenotypes in the F1 generation A genetic cross of inbred snapdragons with red flowers with inbred snapdragons with white flowers resulted in F1-hybrid offspring that all had pink flowers. When the F1 plants were self-pollinated, the resulting F2-generation plants had a phenotypic ratio of 1 red: 2 pink: 1 white. The most likely explanation is: A. pink flower color is epistatic to red flower color. B. pink flowers are the result of a blending of the red and white genotypes. C. flower color is due to 2 or more complementary genes. D. heterozygous plants have a different phenotype than either inbred parent because of incomplete dominance of the dominant allele. E. flower color inheritance in snapdragons does not behave as a Mendelian trait. Incomplete Dominance Practice

28. In codominace, both alleles contribute to the phenotype of the organism. For example, in cattle the allele for red hair is codominant with the allele for white hair. Cattle with both alleles are roan, or pinkish brown, because their coats are a mixture of both red and white hairs. In certain varieties of chickens, the allele for black feathers is codominant with the allele for white feathers. Heterozygous chickens appear speckled with black and white feathers. Codominance

29. Human blood type is determined by codominant alleles. There are three different alleles, known as IA, IB, and i. The IA and IB alleles are co-dominant, and the i allele is recessive. The possible human phenotypes for blood group are type A, type B, type AB, and type O. Type A and B individuals can be either homozygous (IAIA or IBIB, respectively), or heterozygous (IAi or IBi, respectively). A woman with type A blood and a man with type B blood could potentially have offspring with which of the following blood types? A. type A B. type B C. type AB D. type O E. all of the above Codominant alleles: The human ABO markers

30. Codominant Practice: Predicting human blood types • What are the possible blood types of the offspring of a cross between individuals that are type AB and type O? (Hint: blood type O is recessive) • A. AB or O • B. A, B, or O • C. A or B • D. A, B, AB, or O • E. A, B, or AB

31. Sickle cell disease is a common genetic disorder inherited in a codominant fashion, and mainly found in African Americans. Sickle cell disease is characterized by the bent and twisted shape of the red blood cells These sickle-shaped red blood cells are more rigid than normal cells and tend to get stuck in the capillaries, the narrowest blood vessels in the body. As a result, blood stops moving through these vessels, damaging cells and tissues beyond the blockage. Sickle cell disease produces physical weakness and damage to the brain, heart, and spleen. In some cases, it may be fatal. Sickle Cell Disease 

32. Hemoglobin is the protein that carries oxygen in the blood. Mutation: the amino acid valine in place of glutamic acid. As a result, the abnormal hemoglobin is somewhat less soluble than normal hemoglobin. Blood gets stuck in cappillaries. Sickle Cell Disease 

33. Why do so many African Americans carry the sickle cell allele? • Most African Americans can trace their ancestry to west central Africa. • Malaria, a serious parasitic disease that infects red blood cells, is common in this region of Africa. • People who are heterozygous for the sickle cell allele are generally healthy and are resistant to malaria.

34. Many genes have more than two alleles and are therefore said to have multiple alleles. This does not mean that an individual can have more than two alleles. It only means that more than two possible alleles exist in a population. One of the best-known examples is coat color in rabbits. Full color, albino, himalayan, chinchilla A rabbit’s coat color is determined by a single gene that has at least four different alleles. ABO blood groups have three forms of alleles. Multiple Alleles

35. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Coat Color of Rabbits Chinchilla Albino Light gray Dark gray Himalayan

36. Section 14-1 Blood Groups Safe Transfusions Antigen on Red Blood Cell Phenotype (Blood Type Genotype From To Go to Section:

37. Epistasis: • The result of one allele hiding the effects of another allele. • Ex: Labrador’s coat color can vary from yellow to black

38. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Epistasis • Variety is the result of one allele hiding the effects of another allele. eebb E_B_ eeB_ E_bb No dark pigment present in fur Dark pigment present in fur

39. Many traits are produced by the interaction of several genes. Traits controlled by two or more genes are said to be polygenic traits. Polygenic traits often show a wide range of phenotypes. Ex: skin color, eye color, height, and fingerprint pattern Polygenic Traits 

40. Most traits are controlled by two or more genes and are, therefore, called polygenic traits. Each gene of a polygenic trait often has two or more alleles. As a result, one polygenic trait can have many possible genotypes and even more possible phenotypes. Polygenic Traits: EX: height (A bell-shaped curve is also called a normal distribution)

41. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Environmental Influences • Environmental factors • Diet and exercise • Sunlight and water • Temperature

42. Checkpoint Point Questions: 1. Explain what independent assortment means. 2. Describe two inheritance patterns besides simple dominance. 3. What is the difference between incomplete dominance and codominance? 4. Identify examples of polygenic traits and multiples alleles. (one example for each)