2. © K. Malone, 2005 Chapter 11 Introduction to Genetics Gregor Mendel and his work (Section 11-1) –Peas and Genetics –Genes and Dominance Probability and Punnett Squares ( Section 11-2) Exploring Mendelian Genetics (Section 11-3) –Independent Assortment –Mendel’s principles Beyond Mendelian Genetics

3. © K. Malone, 2005 X First Generation (F1) 100% pink!!! Second Generation (F2) X 3 pink, 1 blue - ¾ pink (75%), ¼ blue (25%) How did this happen?

4. © K. Malone, 2005 Section 11-1 Genetics!!! Patterns of Inheritance You inherit traits (physical characteristics) from your parents- Heredity! Heredity is what makes you unique –Examples of Traits: Blue, Green, Brown, Black, Hazel Eye color Red, Brown, Black, Blonde hair color Pale, Olive, Dark skin color Tall, short, average heights Or, pink and blue fur! GeneticsGenetics = the scientific study of heredity and its importance in biology Box 1 Box 2 Box 3 Box 1

5. © K. Malone, 2005

6. Gregor Mendel Gregor Mendel (1822), an Austrian monk who studied inheritance patterns in pea plants, his work is now considered the foundation of modern genetics –He worked with ordinary garden peas, planted in the garden at his monastery. –His love of plants and science allowed him to spend a lifetime devoted to both. In 1866, he published a groundbreaking work that later became known as Mendel’s Laws on Heredity, but NO ONE BELIEVED HIM!!! Years later, his work was rediscovered, and modern genetics was born Ah! What a lovely flower! Yet another lovely flower! I am truly in heaven! Am I in heaven? Box 4

7. © K. Malone, 2005 What Mendel Did Background: –Fertilization = when the female’s egg and the male’s sperm (flower sperm = pollen) unite to produce an embryo Plants, animals, and most living things, sexually reproduce Sexual reproduction = combination of egg and sperm to create a new cell, or embryo True-BreedingMendel’s peas were True-Breeding, meaning if they were allowed to self-pollinate, they would produce baby pea plants (offspring) identical to themselves –Mendel knew what to expect from his pea plants- they should look exactly like their parent plant! He Cross-pollinated his pea plants, mixed up the parents, to see what the resulting plants would look like Let’s cross you with the white flower. Hmm, what have we here? Box 5 Box 6 Box 7

8. © K. Malone, 2005 Box 11 What Mendel Found Mendel studied 7 different pea plant traits that varied from one individual plant to the next (like human traits!) These traits had 2 forms, such as either green seeds or yellow seeds, smooth pods or wrinkled pods –He crossed plants with each of the 7 contrasting characteristics and studied their offspring P = represents the parent generation F (from the Latin word fillius and filia- son and daughter) F 1 = first generation F 2 = second generation Hybrids = offspring of crosses between parents with different traits Are you an F 1 or F 2 ? P x P F1F1 X F 1 F2F2 Box 8 Box 9 Box 10

9. © K. Malone, 2005 Mendel’s Experiment P generation tallshort

10. © K. Malone, 2005 Mendel’s Experiment tallshort F 1 generation tall P generation

11. © K. Malone, 2005 Mendel’s Results Seed Shape Seed Color Seed Coat Color Pod Shape Pod Color Flower Position Flower Height wrinkledgreenwhite roundyellowgray constrictedyellowterminalshort smoothgreen axial tall Round dominant Yellow dominant Gray dominant Smooth dominant Green dominant Ha! Those are MY peas! Axial dominant Tall dominant All the F 1 plants expressed only the dominant trait! Box 12

12. © K. Malone, 2005 Mendel’s Principles of Heredity Mendel learned 2 principles from these experiments: 1.Biological inheritance is determined by factors (we call them genes) that are passed from one generation to the next, Genes = chemical factors that determine traits – each trait is controlled by 1 gene that occurs in 2 contrasting forms or alleles Allele = a different form of a gene Hello! Box 13 Box 14Box 15 2. Principle of Dominance: some alleles are dominant and others are recessive Box 13

13. © K. Malone, 2005 Principle of Dominance Eeek! I’m so proud! An organism with a dominant allele for a particular form of a trait will always exhibit that form of the trait In other words, if you have the dominant allele, you will express that dominant trait An organism with a recessive allele for a particular form of a trait will exhibit that form only when the dominant allele is not present In other words, you must have 2 recessive alleles to express the recessive trait I’m Dominant!! Brown eyes = BB or BbBlue eyes = bb Box 16 Box 17 Tall = TT or Tt Short = tt

14. © K. Malone, 2005 Where did the recessive traits go? Mendel wanted to know why all his F 1 plants expressed only dominant traits ????? He wondered, “Had all the recessive traits disappeared? Or were they still present in the F 1 plants?” To answer this question, he allowed his F 1 plants to self- pollinate F 1 X F 1 F2F2 Naughty! Box 18

15. © K. Malone, 2005 Mendel’s Experiment P generation tallshort F 1 generation tall Tall, short, tall, tall

16. © K. Malone, 2005 Mendel’s Experiment P generation tallshort F 1 generation tall F 2 generation tall short Tall, short, tall, tall, tall, tall, tall, tall, SHORT! Ha!

17. © K. Malone, 2005 F 1 Cross Mendel thought the results for his F 1 cross were amazing! All the recessive traits re- appeared in the F 2 offspring! This was due to segregation (separation) of alleles Segregation of the alleles happens when gametes (sex cells) are formed One trait comes from the father, one trait comes from the mother I’m good! Man of the Year All in Box 18

18. © K. Malone, 2005 Segregation TtTtTtTt Tall TtTtTtTt F1F1 X T TT T TtTtTtTt TtTtTtTttt Segregation Gametes F2F2 Hmmm…. Tall Short t Gametes t 3 Tall, 1 Short 3 :1 Ratio

19. © K. Malone, 2005 Genetics and Probability Probability = the likelihood that a particular event will occur For example, tossing a coin Probability of heads = ½ or 50% Probability of tails = ½ or 50% If you flip a coin 3 times in a row, what is the probability of heads each time? Each coin toss is independent of the previous toss, so ½ x ½ x ½ = 1/8 or 13% chance of all heads The way alleles segregate is completely random, like a coin toss (50% chance for each allele) We can use the principles of probability to PREDICT the outcome of genetic crosses Section 11-2 Yeah, I look good. Box 19 Box 20

20. © K. Malone, 2005 Punnett Squares Tt T t Tall = Tt TTTtTt TtTttt TT or tt = Homozygous Tt = Heterozygous TT, Tt, ttGenotype = Phenotype =Tall, short X Why didn’t I think of that? Punnett Squares = tool used to predict and compare the genetic variations that may result from a cross Box 21 Genotype = genetic makeup (Geno = genes) Box 22 Phenotype = physical characteristics (Pheno = physical) Box 23 Homozygous = 2 identical alleles for the same trait Box 25 Heterozygous = 2 different alleles for the same trait Box 24 Fill in the Punnet Square

21. © K. Malone, 2005 BB Punnett Squares X Phenotype = Brown eyes Genotype = BB or Bb Phenotype = Blue eyes Genotype = bb b b BbBb BbBb BbBb BbBb Genotype offspring = 100% Bb Phenotype offspring = 100% brown eyes B b b b BbBb BbBb bb Genotype offspring = 50% Bb, 50% bb Phenotype offspring = 50% brown, 50% blue eyes B b b B BbBb BbBbBB bb Genotype offspring = 25% BB, 50% Bb, 25% bb Phenotype offspring = 75% brown, 25% blue eyes

22. © K. Malone, 2005

25. ‘Tis my peas against yours! Mendelian Genetics Mendel wondered if the traits segregated independently, or were they somehow linked together His experiment = 2 factor Test Cross for F 1 and F 2 Section 11-3 Round Yellow peas Genotype: RRYY Wrinkled Green peas Genotype: rryy X 100% RrYy, Round Yellow peas Box 26 I won!

26. © K. Malone, 2005 2 Factor Cross: F 2 Mendel’s F 1 plants were RrYy, or all heterozygous for seed shape and color genes Mendel asked himself, “Would these alleles segregate independently? Or would they stay together?” To find out, Mendel crossed his F 1 plants to create the F 2 generation: RrYy x RrYy To segregate or not to segregate, that ‘tis question. X Box 27

27. © K. Malone, 2005 2 Factor Cross: F 2 Alleles for seed shape and color segregated independently Ah, my beautiful peas! F 2 plants : 556 seeds 315 round and yellow (parental) 32 wrinkled and green (parental) 209 combination of phenotypes (combo of alleles) Box 27

28. © K. Malone, 2005 1.Genes, passed from parents to offspring, determine the inheritance of biological characteristics. 2.When 2 or more forms (alleles) of a gene exist, some forms may be dominant and some recessive. 3.In sexual reproduction, each adult has 2 copies of each gene (one from each parent), and these genes segregate from each other when gametes are formed. 4.The alleles for different genes usually segregate independently of one another. Therefore, thou must write all my Principles! Mendel’s Principles Thou must remember my Principles! Box 28 And, stop whining- start writing!!!

29. © K. Malone, 2005 Principle of Independent Assortment Principle of Independent Assortment: genes for different traits can segregate independently during the formation of gametes –This helps to account for the many genetic variations observed in plants, animals and other organisms –Seed color isn’t tied to seed shape or plant height –Just like having red hair doesn’t mean you have blue eyes, or being tall doesn’t mean you have a big nose Genes for different traits are independently assorted into the sex cells (eggs and sperm) Did you know pollen is flower sperm? Box 29

30. © K. Malone, 2005 Exceptions to Mendel’s Rules Some alleles are neither dominant or recessive – what???? Some traits are controlled by multiple alleles or multiple genes Incomplete Dominance = cases when one allele is not completely dominant over another What??? Say it ‘tisn’t so Box 30 Section 11-4

31. © K. Malone, 2005 Incomplete Dominance Pink Flowers! Four o’clock plants Red should be dominant over white, or vise versa, but neither is completely dominant, thus, incomplete dominance. When you cross Red and White Four O’clock Flowers, you get PINK flowers!!!! Box 31

32. © K. Malone, 2005 Codominance Codominance = both alleles contribute equally to the phenotype The offspring is a mixture of both alleles Red cowWhite cow X A pink cow? I don’t think so. Le Moo. Box 32 Roan cow Neither white or red Red fur and white fur Box 33

33. © K. Malone, 2005 Multiple Alleles Multiple Alleles = when a gene has more than two alleles –Does NOT mean a person can have more than two alleles for a single trait (still 1 gene from mom, 1 from dad) –The trait itself has more than 2 forms (alleles) –Ex. Blood types, A, B, AB, O All are a type of human blood But, humans can be either blood type Blood type B = BB or BO Blood type AB = AB Blood type O = OO Blood? I don’t do blood. Where are my peas? Box 34 Blood type A = AA or AO Box 35

34. © K. Malone, 2005 Polygenic Traits Polygenic traits = traits controlled by more than one gene Poly = many, Genic = genes I’m tall. Box 36 If you see a graph like this on my test, or the TAKS test, then you know one gene can’t control the trait! Polygenic! This range of heights and skin colors tells us more than 2 genes control both traits. If 2 genes controlled height and 2 genes controlled skin color, we would see either tall or short people, light or dark skin, and nothing in between. Is that what we see? Box 37

35. © K. Malone, 2005 Drosophila melanogaster Thomas Hunt Morgan (1900s)- worked with Drosophila melanogaster (fruit fly) to study Mendel’s principles Why study fruit flies? –Produce lots of offspring (don’t we know it) –Short life span (can do lots of tests) –Has variations we can cross I prefer flowers. Especially peas. Box 38 So, Mendel’s principles apply to all organisms, no t just plants! Box 38

36. © K. Malone, 2005 Genes and the Environment Genetics is only part of what determines the physical characteristics of an organism Our environment also plays a big role –Your behavior is partially determined by genes inherited from your parents, but also by the environment in which you were/are raised Twin studies –Plants are dependent on weather –Domesticated animals vs. wild animals Wonder twin powers, Activate! Form of.. A pea plant! Box 39 Form of.. Pea soup? So, don’t blame your genes totally for your behavior - that’s mostly learned at home!

37. © K. Malone, 2005 Linkage and Gene Maps Genes are found on chromosomes, and we inherit whole chromosomes from our parents Therefore, it’s actually chromosomes that assort independently, not individual genes So, some genes are “linked” together by virtue of being on the same chromosome Section 11-5 Gene for hair length Gene for curly hair I have curly hair, and I’m tall. Box 40

38. © K. Malone, 2005 Genetic Diversity Even if 2 genes are found on the same chromosome, they may not be linked forever Crossing Over during Prophase I of Meiosis leads to a genetic “mixing” up This generates Genetic Diversity Crossing over Stop that. It’s wrong! Or is it? Box 41

39. © K. Malone, 2005 Gene Maps The further apart two genes are on a chromosome, the more likely they are to be separated during meiosis The rate at which genes were separated and recombined is used to make Gene Maps That doesn’t look like a pea plant. Chromosome 19 Gene Map = shows the location of a variety of genes on a chromosome and how far apart the genes are Box 42

40. © K. Malone, 2005 End of Ch. 11 I hope thou hast enjoyed learning about my work! Go plant some peas! Save the peas! I wonder if anyone will miss me? Will they forget about me and my research? Hmm…pea soup sounds good, I wonder if I have any peas left over?