1. Heredity Why do you look like you look? What made you the way you are? All of your genetic information is contained on your CHROMOSOMES!! GENES are on your chromosomes!! DNA is found on your genes!!

2. Cats – 38 23 from mom Human body cells Each pair has a number from 1-23. Chromosome 1 from dad/mom have similar genetic information. This is also true for the other 22 pairs. Different organisms contain different numbers of chromosomes!! Dogs - 78 46 chromosomes 23 pair of chromosomes 23 from dad

3. These chromosome pairs are called Genes that determine a specific trait are found in the same location on that pair of chromosomes Genes that determine a specific trait are found in the same location on that pair of chromosomes Example: the gene that determines ear shape is located in same place on 2 homologous chromosomes. HOMOLOGOUS CHROMOSOMES

4. Actual (expression) Physical appearance. Genotype determines Phenotype. Those homologous chromosomes carry the genes that make you—YOU!! Those two make up your GENOTYPE Genes passed to offspring. PHENOTYPE

5. Dominant and Recessive Alleles Many traits are controlled by a single gene. Ex.- 1 gene = Earlobes attached 1 gene = Earlobes free 1 gene = Earlobes free Different forms of same gene are called Alleles will be either: Dominant = Stronger Trait Recessive = Weaker Trait Look at the table to the right for examples of human traits. Trait Trait Trait Made By ByDominant Allele Allele Trait Made By By Recessive Recessive Allele Allele HairType Curly or WavyStraight HairColorDarkLight EarlobeFreeAttached DimplesPresentNotPresent ALLELES

6. Identifying Genotypes and Phenotypes Genotype trait is written as 2 letters. The allele that causes free earlobes is dominant over the allele for attached earlobes. So F is used for free earlobe gene. What do you think is used for attached earlobe gene? Lowercase f Dominant Allele-- Capital Letter Recessive Allele-- Lowercase Letter

7. More on Genotypes and Phenotypes Offspring receive 2 copies of each gene-1 from each parent. 3 possible genotypes : FF, ff, or Ff. FF and ff = Homozygous Ff = Heterozygous “Homo” means “the same.” Homozygous genotype – Made up of 2 dominant or 2 recessive alleles. Ex.- FF or ff “Hetero” means “different.” Heterozygous genotype – Made up of 1 dominant and 1 recessive allele.

8. Do your ears hang low? If an organism inherits a dominant allele, the dominant trait is expressed. Allele for free earlobes = dominant. So, how would we write the genotype? ___________________________ FF and Ff How then would we write the genotype for attached earlobes? ___________________________ ff

9. Let’s Stop and Answer Some Questions 1. What do living things inherit and from where? 2. What are some things you can inherit from mom/dad? 3. What are genes? 4. What else do genes do? Give some examples. 5. What do the terms genotype and phenotype mean? 6. Genotype determines ___________________. 7. Where are genes located? 8. What is the job of chromosomes? 9. One chromosome contains many different _____________. 10. How many chromosomes do we receive from mom/dad? For a total of? 11. How many pairs of chromosomes does each human cell have? 12. Describe how the chromosome pairs are numbered and how the genetic information is arranged. 13. What are homologous chromosomes? 14. What are alleles? 15. What is meant by the terms dominant and recessive? 16. Give some dominant and recessive traits. 17. How do you distinguish between dominant and recessive traits when written?

10. Using Punnett Squares Used to predict results of genetic crosses. Cross – Mating of 2 parent organisms Punnett Squares are used to calculate probability of genotypes/phenotypes in offspring.

11. Let’s make a Punnett Square with the information below. Task – Predict outcome of crossing tall pea plant with short pea plant. First, I must know the genotype of each parent plant. There are 3 possible genotypes : TT, Tt, and tt Genotype of pure tall plant : TT <---- It has 2 dominant alleles Genotype of pure short plant : tt <--- It has 2 recessive alleles. To make a Punnett Square, 1 st separate the parent alleles. Place 1 pair across top of square, and other pair down the left side. tt T T Tt Genotype - Genes Dominant Gene always 1 st in genotype tt T T tall Phenotypes - physical

12. Let’s consider a cross between 2 plants with heterozygous genotypes : Tt x Tt T t T t TTTt tt Tall Short How many possible genotypes here?3: TT, Tt, tt How many phenotypes?Tall, Short Probability of tall plants? 3 out of 4, or 75%. Probability of short plants? 1 out of 4, or 25%.

13. We’re done! Let’s answer some questions. Discussion Question Suppose you crossed a pea plant that has round seeds (R) with a pea plant that has wrinkled seeds (r). If 50 percent of the offspring have round seeds and 50 percent of the offspring have wrinkled seeds, what are the genotypes of the parent plants? Make a Punnett Square to help you answer the question. 1. 2 different forms of the same gene are called A. phenotypes. C. dominant traits B. genotypes. D. alleles 2. An organism’s expressed traits make up its A. recessive traits C. phenotype B. genotype D. alleles 3. A pea plant that is homozygous dominant for seed color is crossed with a pea plant that is homozygous recessive for seed color. Since yellow is the dominant color, the letters Y and y represent the genes for seed color. What cross represents these 2 plants? A. Yy x Yy C. YY x yy B. YY x Yy D. Yy x yy 4. You meet a person and notice that she has dimples. What can you say for sure about the phenotypes of her parents? A. At least 1 of her parents has dimples. C. Neither parent has dimples. B. Both of her parents have dimples. D. 1 of her parents does not have dimples.