Chapter 11: Introduction to Genetics (p.306)

1. Chapter 11: Introduction to Genetics (p.306)

2. Q: Are all mutations harmful? • Write an answer with ONE SENTENCE explaining your response. Include an example that supports your claim.

3. Gregor Mendel (July 20, 1822 – January 6, 1884) • Austrian Friar • Monastery gardener who raised pea plants and traced their genes through hundreds of generations • “Father of genetics” • His work was not widely accepted until the mid 1900’s http://www.youtube.com/watch?v=aDpLDBaEBjk&feature=related http://www.youtube.com/watch?v=aoVeSncKFAY&feature=related

4. Mendel’s Peas • Anthers = Male structure, produce pollen • Pistil = Female structure, produces ova (eggs) • Peas can self-pollinate Or cross-pollinate

5. Cross-pollination • Mendel used true-breeders (purple) • He cut off the anthers of some before they developed pollen • Then he cross-pollinated plants with paintbrushes • Offspring now had 2 parents instead of 1

6. B. Genes and Dominance • P = Parental generation • F1= First filial or first “child” generation • F2= Second Filial generation, and so on. • Filius is Latin for “son”

7. Genes and Dominance • Gene: chemical factors that determine traits • locus(loci)=location of gene on the DNA • Allele: different forms of a single gene • ex. White or purple flowers

8. Principle of Dominance • some alleles are dominant and others are recessive--recessive traits are “masked” by dominant ones. • Hybrids are offspring produced by two parents with different traits

9. Pea Traits • Mendel studied 7 traits in peas and tracked how they were passed down for many generations • He recorded the information each season for over 40 years!

10. Inheritance of Color in Pea Seeds • Yellow peasare dominant • Green peas are recessive

11. Gametes • Sex cells only carry one allele each • One allele will come from each parent • Humans have sperm and eggs, plants have pollen and ova

12. Other Vocabulary words. . . • Phenotype = visible expressed trait (what does it look like or do?) • Genotype = combination of genes (letters) The genotype determines the phenotype • Homozygous = an individual with 2 alleles for the same gene (AA or aa) • Heterozygous = an individual with both alleles (Aa)

14. II. Genetics and Probability • Probability= the likelihood that a particular event will occur • Coin Flip (Ratio of heads:tails) Once: 50:50 (1/2 of the time it is heads, ½ tails) Q: If you flip a coin 3 times, what is the likelihood of getting three heads? • Multiply the probability of each event • ½ x ½ x ½ = 1/8

15. Punnett Squares • A table of the possible outcomes from a cross between 2 parents

16. Rules for Punnett Squares (p.316) • Start with the parents • Figure out the possible gametes • Line them up on the square • Fill in the table by combining the traits • Determine the possible genotypes and phenotypes of each offspring • Write the RATIO and PERCENT CHANCE of these possibilities

18. Punnett Squares (continued) • True-breeding = Homozygous (TT or tt) • Heterozygous (Tt) means they have both alleles • Phenotype: physical expressed characteristic • Ex: Yellow or green peas; blue or brown eyes • Genotype: genetic makeup (TT, tt, Tt) The genotype determines the phenotype

19. C. Other genetic factors • Incomplete dominance • Cases in which neither trait is dominant and the heterozygous individual expresses an even mix of the trait • Miribalis flowers • Red = R • White = W • Pink = RW

20. Incomplete Dominance • In Miribalis flowers, a red parent + white parent results in all pink offspring • Red = R • White = W R R • Pink = RW W • Phenotype = 4:0 • Genotype = 4:0 W

21. Codominance • A mix of dominant and recessive trait is expressed like a blend (ex. Roan cattle) + =

22. Codominance (use capital letters) • In cattle, a red parent + white parent results in both traits being expressed equally • Red = R • White = W RR • Roan (spots) = RW W • Phenotype = 4:0 • Genotype = 4:0 W

23. Codominance • In people a parent with straight hair + a parent with curly hair results in both traits being expressed equally (Wavy hair) • Straight = S S S • Curly = C C • Wavy = SC • Phenotype = 4:0 C • Genotype = 4:0

24. Multiple alleles • more than 2 alleles control the expression of the gene (Fur color in rabbits, see p. 273 in Blue text)

25. Polygenic traits • Traits controlled by more than 2 different genes (ex. Skin color in humans)

26. III. Exploring Mendelian Genetics • Are there relationships between the different alleles? • Mendel wondered if wrinkled seeds must always be yellow or if smooth seeds must also be round • Crossed plants and looked for patterns with 4 different alleles (2 traits) DIHYBRID CROSS

27. Dihybrid Cross (RrYy x RrYy) • Mendel tracked two traits to see if there were links between the inheritance of traits • Round = R • Wrinkled = r • Yellow = Y • Green = y • Phenotype = 9:3:3:1 • Round Yellow: wrinked Yellow:Round green:wrinkled green

28. A. Independent Assortment • Principle of independent assortment: genes for different traits can segregate independently during the formation of gametes • We end up with a phenotype ratio of 9:3:3:1 • Genotype ratio of 2:2:2:2:2:2:1:1:1 • Out of 16 offspring looking at 2 traits

29. B. Mendel’s Principles • Inheritance of traits is determined by genes. In sexual reproduction, genes are passed from parents to their offspring • There are dominant and recessive forms of most genes that are expressed by different traits • Each adult has 2 alleles for each gene (1 from each parent). Genes are segregated in gametes (sex cells only carry one allele) • Alleles of genes segregate independently of one another

30. Genetic Diseases: Muscular Dystrophy • Genetic muscle disease • Dominant allele • 50% chance of inheritance in offspring between an affected and an unaffected pair