1. Intro to Genetics November 2014

2. Heredity Study of the transmission of characteristics from parent to offspring. The field of genetics began with the work of Gregor Mendel

3. The Work of Gregor Mendel About Mendel –Began his work in 1860s –Breeded & studied garden pea plants –Published paper in 1866 stating that parents pass on discrete “heritable factors” (genes) on to their offspring Remember that genes are segments of DNA that code for traits –Considered “Father of Genetics”

4. Plants used in Experiments Mendel probably studied pea plants because of their short generation time, plentiful offspring & visible varieties –Traits: Variations of genetic characteristics. These pea plants are usually self- pollinating (sperm cells in pollen fertilize egg cells located in ovary on the carpel in the same flower) –This is an example of Sexual Reproduction (Male & female gametes fuse to form a zygote.)

5. What Mendel Did He prevented self- pollination by cutting off male stamens (w/ pollen) Transferred pollen from other plants onto stigma located on carpel. This is called cross breeding- crossing plants w/ different characteristics

6. Traits Mendel Studied

7. Mendel’s work Mendel crossed “true breeding” (plants that produced offspring identical to parents after self- pollinating) tall pea plants with true-breeding short pea plants (P generation) All of the offspring (F 1 generation) were tall When he allowed the first- generation tall plants to self- pollinate, three-fourths of the offspring (F 2 generation) were tall and one-fourth were short.

8. Pea Plant Generations Parental generation (P) - original crossed plants First Filial (F 1 ) generation- offspring of P generation F 2 generation- second generation made when two F 1 generation plants breed

9. Results of Mendel’s Experiments 1.Alternate forms of genes (alleles) produce variations in inherited characters 2.For each character, an organism inherits 2 alleles (one from each parent) 3.Principle of dominance 4.Law of Segregation 5.Law of Independent Assortment

10. Principle of Dominance Principle of Dominance- some alleles are dominant while others are recessive –Dominant- when that allele is present that trait will be exhibited –Recessive- masked trait when dominant allele present

11. Important Vocabulary Homozygous- organisms w/ two identical alleles for a trait (TT or tt) This is also called purebred. Heterozygous- have different alleles for a trait (Tt). This is called hybrid. Genotype- genetic makeup described with letters (TT, Tt or tt) Phenotype- physical characteristics described with words like tall or short

12. Law of Segregation Applies to sexual reproduction Individuals have two alleles of each gene. When gametes are produced, each gamete receives one of these alleles. During fertilization, these gametes randomly pair to produce four combinations of alleles.

13. Law of Independent Assortment Each pair of alleles assorts independently of other pairs of alleles during gamete formation The inheritance of one character has no effect on the inheritance of another For example- –Pea plant with genotype AaBb –A and a will separate from one another and B and b will separate from each other –These alleles can then recombine in four different ways.

14. Probability and Punnett Squares Probability- likelihood that a particular event or trait will occur. Probabilities are more accurate with bigger samples Punnett squares- diagram used to predict gene combinations

15. Crosses Hybrid: Offspring of parents that have different forms of a trait (Ex. tall & short) Punnett squares can represent different types of crosses –Monohybrid Cross: Two parents that differ from each other by a single trait. –Dihybrid Cross: Cross between two parents involving two different traits (Ex. Round/Yellow & Wrinkled/Green)

16. Punnett Squares Dominant allele is represented with a capital letter. When capital letter is present, that phenotype is usually exhibited. Always write dominant letter first. Recessive allele is represented with a lower case letter. Phenotype exhibited when homozygous recessive (tt)

17. Setting up a Punnett Square Monohybrid Cross (One trait) Female genotype across top Male genotype across side Ex: Mother Tt, Father Tt Tt T t

18. Problem: P Generation Mother is homozygous tall TT Father is heterozygous tall Tt TtTt T TT Tt Genotype: F 1 2TT:2Tt or 1/2TT:1/2Tt or 50%TT:50%Tt Phenotype: F 1 4 tall or 100% Tall

19. T t T t F 1 Cross Father Tt Mother Tt TTTt tt Genotype: 1TT: 2Tt: 1ttPhenotype: 3Tall:1short 1/4 TT: 1/2 Tt: 1/4 tt3/4 Tall: 1/4 short 25%TT: 50%Tt: 25%tt75%Tall: 25%short