CHARACTERISTICS OF LIFE

1. CHARACTERISTICS OF LIFE All Living Things reproduce!!! All Living Things Have DNA!!!

2. WHY ARE WE ALL DIFFERENT? We all inherited different genes from our parents which determines our traits. Heredity – Passing on of genes which determine your traits from parents to offspring. 23 chromosomes from each parent.

3. Genes – Pieces of DNA that carry hereditary instructions and are passed from parents. Traits – A distinguishing characteristic that is passed from parents to offspring. Genetics – Study of heredity (passing on of genes)

4. Johann Gregor Mendel was born July 22, 1822. Mendel became a friar at the Augustinian monastery in Brno, Czechoslovakia. From 1868 until his death, Mendel was the abbot of the monastery. Mendel was experimenting with flowers in the monastery's gardens. He wondered how traits were passed from parent to offspring. He studied the relations between parents and offspring with mathematical symbols. His favorite plants to experiment with were peas. FATHER Of genetics

5. MENDEL’S EXPERIMENT PART 1 He bred a tall pea plant with a pure short pea plant. But ALL the offspring were TALL. How could that be? Maybe a mistake was made? PART 2 He crossed 2 of the offspring from the above cross. Results – 75% Tall 25% Short Now wait a minute!! He crossed two tall and go a short? What’s going on?????

6. GENETIC RULES Every organism has TWO forms of a gene for each trait. One from each parent. Each form is called an ALLELE. You can receive a dominant or recessive gene from your parent.

7. GREGOR MENDEL He realized in the first cross, one trait appeared and the other seemed to be masked. * The trait that masks or is stronger than the other trait is called the dominant trait. * The trait that is covered up is called the recessive trait. For these reasons, Mendel is called the Father of Genetics.

8. GENETICS RULES and SYMBOLS Scientists use symbols to represent different forms of a gene. Capital Letters – Represents dominant trait. Dominant traitsare the stronger traits. Lower Case Letters – Represents recessive trait. Recessive traitsare the weaker traits that are often masked by dominant traits. Examples-BB – brown eyes bb - blue Bb – brown eyes

9. Example Dominant Traits Brown Eyes- B Widow’s Peak- W Unattached Earlobes- E Freckles- F Example Recessive Traits Blue eyes- b Straight hairline- w Attached earlobes- e No Freckles- f

10. Homozygous vs. Heterzygous If the inherited genes (alleles) are the same, then they are called HOMOZYGOUS or purebred.Letters are the same size. Examples – aa , AA , LL , ll , TT , tt If the inherited genes are different, then they are called HETEROZYGOUS or hybrid. Letters are different sizes. Examples – Aa , Ll , Tt, Bb

11. Genotype vs. Phenotype The genotype is the letter combination or gene combinations Example – Tt, Aa, bb,or Ll The phenotype is the actual appearance of the organism. Example – tall, brown hair, blue eyes, long toes

12. GENETIC PROBABILITY Mendal crossed yellow and green pea plants and discovered that 1 out of 4 were green. He was using probability. Probability – The possibility or likelihood that a particular event will occur. Used to predict the results of genetics crosses.

13. PUNNETT SQUARES A Punnett square is a special chart used to show the possible gene combinations in a cross between 2 organisms. (also called monohybrid crosses) Developed by an English geneticist by the name of Reginald Punnett.

14. PARTS OF A PUNNETT SQUARE Male Genes Female Genes Offspring Combinations T= tongue roll t= cannot roll tongue

16. How does a Punnett Square Work? • Draw a square and divide • it into 4 sections. • Write the gene pairs across the top of the box, then the • other down the side. • In each box, place the correct gene to see the possible combinations. Each square represents a 25% possibility of getting that trait.

17. Cross between homozygous dominant curly tail (TT) and a homozygous recessive straight tail (tt). Tt Tt Tt Tt

18. Tt Tt Tt Tt What are the percentages of the offspring? What are the genotypes? What are the phenotypes?

19. Cross between two heterozygous curly tailed parents (Tt). TT Tt tt Tt What are the percentages of offspring? What are the genotypes? What are the phenotypes?

20. Mathematical Computations In a Punnett Square where both parents are hybrids the percents are listed below: 25% purebred (homozygous) curly – TT 50% hybrid (heterozygous) curly - Tt 25% purebred (homozygous) straight - tt 50 % % of same genotype as parents - % of same phenotype as parents - 75%

21. T- height S-shape T-tall t-short S-square s-round Dihybrid Crosses A dihybrid cross is a cross of two different traits List of gamete genotypes: Mom- Dad-

22. Dihybrid crosses- formation of zygote Mom- ST, St, sT, st Dad- ST, St, sT, st When parent gametes (egg/sperm) join to form a zygote, the possible offspring gene combinations are as follows:

23. Dihybrid Crosses • Parent generation = gene pairs given by parents. • Gametes = half of parent gene pair • 1st Generation= combination of gametes to produce offspring. • 2nd Generation= possible combination of offspring from 1st generation cross • The possible gene combinations from 1st generation offspring

24. Practice G-eye size • G-large • g-small B- eyebrows • B-separated • b-attached

25. The squares contain the gene combinations that could occur in the cross. The genotype is the letter combination or gene combinations in the squares. Example – Tt, Aa, bb,or Ll The phenotype is the actual appearance of the organism. Example – tall, brown hair, blue eyes, long toes

26. INCOMPLETE DOMINANCE Sometimes, you may notice that traits can blend together. Two capital letters are used. For example: Red & White are equally dominant producing Pink flowers. Examples – roan color in horses and cows, pink color in flowers are red and white combined.

27. Codominance When both alleles contribute to the phenotype. For example: Chickens- black & white feathers are codominant, therefore they can appear speckled.