1. TEKS 6F: Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-Mendelian inheritance. How are offspring influenced by genetic combinations? Traits are controlled by factors that pass from parent to offspring. These factors are called genes. The different forms of a gene are alleles. Mendel’s principle of dominance states that some alleles are dominant and others are recessive. The recessive allele is exhibited only when the dominant allele is not present. When both alleles are the same, the individual is homozygous for that trait. When the alleles are different, the individual is heterozygous for the trait. (contd.)

2. TEKS 6F: Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-Mendelian inheritance. The separation of alleles is called segregation. When gametes (sex cells) form, alleles segregate so that each gamete carries only one allele for each gene. The offspring gets a new combination of alleles: one from each parent. The genetic makeup of an organism is called its genotype. The organism's physical traits are its phenotype. 1. Predict What is an organism’s genotype if it receives two recessive alleles for height (T=Tall, t=short)?

3. TEKS 6F: Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-Mendelian inheritance. How can you predict the outcomes of monohybrid crosses? When doing a genetic cross, the parent organisms are the P, or parental generation. The offspring are called the F 1, or first filial generation. A monohybrid cross is a cross in which there are two contrasting alleles for a single gene. A Punnett square is a diagram that helps predict combinations in genetic crosses. Punnett squares are easy to construct. 2. Define What is a monohybrid cross?

4. TEKS 6F: Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-Mendelian inheritance. How do you make a Punnett square?

5. TEKS 6F: Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-Mendelian inheritance. How can you predict the outcomes of dihybrid crosses? A dihybrid cross is one in which there are two genes. The principle of independent assortment states that genes for different traits could segregate independently during the formation of gametes. To construct a Punnett square for a dihybrid cross, follow the same steps. 3. Compare and Contrast What is the difference between a monohybrid cross and a dihybrid cross? (contd.)

6. TEKS 6F: Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-Mendelian inheritance.

7. What are some other patterns of inheritance? In incomplete dominance, alleles are neither dominant nor recessive. Instead, the heterozygous phenotype lies somewhere between the two homozygous phenotypes. 4. Predict Using the example of the four o’clock flowers, what would be the genotype of the parents if all offspring were red? In four o’clock plants, the alleles for red and white flowers show incomplete dominance. Heterozygous (RW) plants have pink flowers—a mix of red and white coloring.

8. TEKS 6F: Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-Mendelian inheritance. What is codominance? In codominance, the phenotypes produced by both alleles are clearly expressed. For example, in certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers. Heterozygous chickens have a color described as erminette, speckled with black and white feathers.

9. TEKS 6F: Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-Mendelian inheritance. What are multiple alleles? Many genes exist in several different forms and are therefore said to have multiple alleles. A gene with more than two alleles is said to have multiple alleles. One of the best-known examples is human blood type. There are three alleles for blood type, A, B, and O, which combine to give us the familiar blood types of A, B, O, and AB.

10. TEKS 6F: Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-Mendelian inheritance. What are polygenic traits? Many traits are produced by the interaction of several genes. Traits controlled by two or more genes are said to be polygenic traits. The variety of skin color in humans comes about partly because more than four different genes probably control this trait. The environment can also affect the way in which an organism’s genes are expressed. 5. Compare and Contrast What is the difference between multiple alleles and polygenic traits?

11. TEKS 6F: Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses, and non-Mendelian inheritance. Some forms of inheritance are distinctly non-Mendelian inheritance because they do not follow the principles described by Gregor Mendel. For example, sometimes the color of a particular plant’s leaves depend only upon the color of tissue in the female parent, which produces the egg cells within its flowers. This is known as maternal inheritance. Human mitochondrial disorders also show a maternal pattern of inheritance. In recent years, a new phenomenon has been added to the list of non-Mendelian patterns of inheritance. DNA bases in certain genes can be chemically modified so that they are not expressed in the next generation. This process is known as genetic imprinting. 6. Define What is meant by non-Mendelian inheritance? What is non-Mendelian inheritance?