1. CHAPTER 11 Introduction to Genetics

2. GENETICS & YOU Something to keep in mind as we begin our discussion on genetics… Your traits are a combination of your genetic material (DNA) and the environment around you. For Example: Why are people from poor countries often short?  Malnutrition Because of this… cannot The physical appearance of an individual cannot always be directly linked to an individual’s genetic makeup.

3. NATURE VS. NURTURE What can we use to study how the environment affects the expression of our genes?

4. GREGOR MENDEL Considered the “Father of Genetics” Performed Experiments to Study Heredity Heredity – the passing of traits or characteristics from parent to offspring In his experiments Mendel used Pea Plants. Why?

5. MENDEL’S PEA PLANTS 1.Cheap & Readily Available 2.Easy to Grow & Don’t Move (easy to contain & control/manage) 3.Grow fast –study multiple generations 4.Control their breeding/reproduction 5.Characteristics were easy to study because they came in easily identifiable pairs. a) Round vs. Wrinkled Pea Shape b) Tall vs. Short Pea Plants c) Green vs. Yellow Pea Pods

6. MENDEL’S EXPERIMENT Mendel controlled the reproduction of his pea plants so he could study heredity. He did this by:  Removing the Stamen (male)  Contains the Anther  Pollen = Plant Sperm  Carpel (contains the stigma, style, ovary) – female reproductive structures Crossed Plants that showed the same traits only. Created “true or pure bred” lines

7. MENDEL’S EXPERIMENT Once Mendel had his true or pure bred lines, he could cross plants that had different traits. What did Mendel look for?  Patterns!

8. OBSERVATIONS So what did Mendel observe when he performed his experiments? ________________ X ___________________ All _________________________ ____________________ x ______________________ Ratio 3 ( ) __________________: 1 ( ) _________________

9. DOMINANT VS. RECESSIVE Traits like pea shape are said to be either dominant or recessive. A recessive trait become hidden by a dominant trait. In Mendel’s cross which trait was dominant? Which trait was recessive? How do we know recessive traits are present & get passed down?

10. MENDEL DIDN’T KNOW ANYTHING ABOUT GENES! Gene – segment of DNA that codes for a specific protein which controls a trait. Genes can exist in more than one form! For example  Round or Wrinkled are 2 forms of the gene or protein for seed shape. We call these different forms of a gene: alleles Each parent has 2 alleles for each trait BUT only gives one to the offspring! Which one? That’s all chance!

11. PROBABILITY & GENETICS Diploid Organisms have 2 copies of each numbers chromosome. Remember, chromosomes of the same shape and size are called:  Homologous Chromosomes Homologous Chromosomes carry the same genes but can have different forms or alleles of these genes. For Example: Both chromosomes 18 carry the gene that controls the shape of your hair line. (one chromosome 18 came from mom & one from dad) 18 A – Widow’s Peak 18 B – No Widow’s Peak So, which one will you pass on to your child?

12. PROBABILITY & GENETICS Scientists can make predictions about which traits will get passed onto offspring & therefore what offspring might look like. The study of these predications is called probability. Probability  Expressed as a fraction or a percent.  Equation: # of times a specific event occurs total # of possible outcomes  can be either dependent or independent

13. INHERITANCE OF ALLELES Mendel crossed plants that differed in one gene/trait: pea shape. This type of cross is called a monohybrid cross. ________________ X ___________________ All _________________________ ____________________ x ______________________ Ratio 3 ( ) __________________: 1 ( ) _________________

14. GENERATIONS & PUNNETT SQUARES The plants involved in the 1 st cross are called the parental or P generation. The offspring of the P generation are called the F1 generation. The offspring of the F1 generation are called the F2 generation. Punnett Square Capital Letter represents the: Dominant Allele Lowercase Letter represents the: Recessive Allele Place each parent’s allele combinations across the top & side of the box & fill in the squares.

15. GENOTYPES & PHENOTYPES Both RR pea plants & Rr peal plants look round, but are they the same genetically? Round is called a phenotype = physical appearance Rr or RR is called a genotype = actually genes or alleles of an individual Two Types of Genotypes  Homozygous = two identical alleles (RR or rr)  Heterozygous = two different alleles (Rr)

16. GENOTYPES & PHENOTYPES Classify the following as either a genotype or phenotype. For each genotype determine if it is homozygous or heterozygous. RRRoundRr

17. GENOTYPES, PHENOTYPES, & PUNNETT SQUARES MUST Every time you make a Punnett Square you MUST indicate both the Phenotypic & Genotypic Ratios! Let’s do an Example: homozygous round pea X heterozygous round pea