11-1: The Work of Gregor Mendel Called the “Father of Genetics” Austrian monk, spent time teaching high school age students and tended the monastery garden. YouTube - Mendel - From the Garden to the Genome

Genetics - the study of heredity Heredity - passing on of characteristics from parents to offspring

Mendel used “Self-pollinating” peas to produce future offspring Knew that each flower produces both male (sperm –found in pollen) and female (egg) gametes Fertilized flower’s egg with its own sperm Produced what he called “true - breeding” Offspring would be genetically identical

Mendel experimented with cross-pollination. He cut the pollen-bearing anther off of the flowers and applied pollen from different flowers to the stigma (the part that catches pollen)

So with cross-pollination what did Mendel expect? A: Probably a blend of both parents. What did he get? A: Not really what he expected.

Trait – specific characteristic that varies from one individual to Genes and Dominance Trait – specific characteristic that varies from one individual to the next Important that Mendel used traits that were unambiguous Mendel’s seven traits: Seed coat color Seed color Seed shape Pod color Pod shape Plant height Flower position

Mendel crossed true breeds with each other (P generation–“parental”) Offspring known as F1 Plants that were products of cross -pollination are known as “hybrids.” F1 generation was not a blend of parental characteristics. Instead….

Mendel’s Monohybrid Cross – P to F1 A Punnett square, something we’ll cover in a moment. Huh?!?....all yellow seeds!!!

In fact………here’s what happened with the rest of the traits.

Figure 11-3 Mendel’s Seven F1 Crosses on Pea Plants Section 11-1 Seed Shape Seed Color Seed Coat Color Pod Shape Pod Color Flower Position Plant Height Round Yellow Gray Smooth Green Axial Tall Wrinkled Green White Constricted Yellow Terminal Short Round Yellow Gray Smooth Green Axial Tall

Short and tall = alleles Mendel concluded that heredity is dictated by chemical factors called genes (About 100 years later before Watson & Crick and the whole DNA thing) Genes have alternate forms depending on the plant These alternate versions of the same gene are called alleles Plant height = gene Short and tall = alleles Both alleles are present. One type (recessive) can only be expressed if the other (dominant) is not present All these are found on chromosomes!!

Genes, Alleles, and Chromosomes

What happened to the other traits? Mendel allowed the F1 plants to self-pollinated The “other” (recessive) traits reappeared in the F2 He was surprized, I’m sure…

Principles of Dominance Section 11-1 P Generation F1 Generation F2 Generation Tall Short Tall Tall Tall Tall Tall Short

Principles of Dominance Section 11-1 P Generation F1 Generation F2 Generation Tall Short Tall Tall Tall Tall Tall Short

Principles of Dominance Section 11-1 P Generation F1 Generation F2 Generation Tall Short Tall Tall Tall Tall Tall Short

Segregation – separation of alleles How did the alleles get separated? Segregation – separation of alleles Mendel suggested the alleles segregated when the gametes formed. So every sperm or egg cell has one version (allele) for that gene Some (50%) have allele for tall, others (50%) have allele for short

Law of Segregation- the 2 alleles separate when gametes are formed Law of Independent Assortment- one trait doesn’t affect the inheritance of another (purple/white flowers has nothing to do with smooth/rough pod)

Genes, Alleles, and Chromosomes

Lab Activity Interest Grabber Tossing Coins Section 11-2 Lab Activity Tossing Coins If you toss a coin, what is the probability of getting heads? Tails? If you toss a coin 10 times, how many heads and how many tails would you expect to get? Working with a partner, have one person toss a coin ten times while the other person tallies the results on a sheet of paper. Then, switch tasks to produce a separate tally of the second set of 10 tosses.

Interest Grabber continued Section 11-2 1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected? 2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected? 3. If you compiled the results for the whole class, what results would you expect? 4. How do the expected results differ from the observed results?

11–2 Probability and Punnett Squares A. Genetics and Probability Section Outline Section 11-2 11–2 Probability and Punnett Squares A. Genetics and Probability B. Punnett Squares C. Probability and Segregation D. Probabilities Predict Averages

11-2: Probability and the Punnett Square Probability – likelihood of an event to take place What are the chances for a coin to be flipped heads three times in a row? ½ X ½ X ½ = ⅛ Probability explains everything in predicting outcomes of genetic crosses.

Punnett Squares Possible gene combinations are represented showing a Punnett Square. Homozygous – same allele (SS or ss) Heterozygous - different allele (Ss) Genotype – genetic makeup (SS, Ss, ss) Phenotype – physical feature observed (Smooth, wrinkled)

Probability and Segregation Characters investigated by Mendel Consistency is Good No matter what the characteristic, Mendel observed a 3:1 ratio of characteristics in the F2.

Monohybrid Crosses Yielded Consistent Results Therefore, the Principle of Segregation indeed is a general principle of genetics.

Probabilities Predict Averages The more times you flip a coin, the closer it will be to the expected result Consequently the more offspring that an organism has, the closer the results will be to the averages. This is why scientists perform MANY experiments. Avoid the small percentage event and assume it is the trend.

Interest Grabber Height in Humans Section 11-3 Height in Humans Height in pea plants is controlled by one of two alleles; the allele for a tall plant is the dominant allele, while the allele for a short plant is the recessive one. What about people? Are the factors that determine height more complicated in humans?

Interest Grabber continued Section 11-3 1. Make a list of 10 adults whom you know. Next to the name of each adult, write his or her approximate height in feet and inches. 2. What can you observe about the heights of the ten people? 3. Do you think height in humans is controlled by 2 alleles, as it is in pea plants? Explain your answer.

11–3 Exploring Mendelian Genetics A. Independent Assortment Section Outline Section 11-3 11–3 Exploring Mendelian Genetics A. Independent Assortment 1. The Two-Factor Cross: F1 2. The Two-Factor Cross: F2 B. A Summary of Mendel’s Principles C. Beyond Dominant and Recessive Alleles 1. Incomplete Dominance 2. Codominance 3. Multiple Alleles 4. Polygenic Traits D. Applying Mendel’s Principles E. Genetics and the Environment

Independent Assortment Mendel wondered if alleles for separate genes influenced each other when they segregate. Ex: Does a round seed always have to be yellow, or can it be green? Two-factor cross Followed two separate genes from generation to generation Independent Assortment of Alleles

Two Factor Cross Crossed true bred round/yellow (RRYY) pea plants with wrinkled/green (rryy) plants F1 – 100% round/yellow (RrYy) No surprise to Mendel Mendel hypothesized there was dependent assortment, therefore predicted 3:1 ratio in the F2 (just like in the first experiment) 3 round/yellow : 1 wrinkled/green

Fig. 10.12a Dihybrid cross: F1 generation

Fig. 10.12b Dihybrid cross: F2 generation Ratio: 9:3:3:1

Beyond dominance and recessiveness Incomplete dominance Hybrids (heterozygous) exhibit blend of traits 4 o’clock plants Red and white produce heterozygous pink plants

Figure 11-11 Incomplete Dominance in Four O’Clock Flowers Section 11-3

Figure 11-11 Incomplete Dominance in Four O’Clock Flowers Section 11-3

Chickens with speckled black spots on white feathers Codominance MOO Similar to incomplete dominance however both traits are actually visual instead of blended Chickens with speckled black spots on white feathers Humans have gene for protein controlling cholesterol – if heterozygous two forms are made.

When there are more than two alleles for a particular gene Multiple Alleles When there are more than two alleles for a particular gene Blood type (also demonstrates some codominance) Polygenic traits Traits controlled by many genes Height SLE (Lupus) Weight Eye Color Intelligence Skin Color Many forms of behavior

Applying Mendel’s Principles Good animal to test was fruit fly Drosophilia melanogaster Fast reproductive rate/life cycle and produced many offspring

Environmental impact on gene expression                         Environmental factors/conditions may alter gene expression.   Example: Soil pH and flower color.

Hydranga

How Many Chromosomes? Interest Grabber Section 11-4 How Many Chromosomes? Normal human body cells each contain 46 chromosomes. The cell division process that body cells undergo is called mitosis and produces daughter cells that are virtually identical to the parent cell. Working with a partner, discuss and answer the questions that follow.

Interest Grabber continued Section 11-4 1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis? 2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo? 3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?

D. Comparing Mitosis and Meiosis Section Outline Section 11-4 11–4 Meiosis A. Chromosome Number B. Phases of Meiosis 1. Meiosis I 2. Meiosis II C. Gamete Formation D. Comparing Mitosis and Meiosis

Process of turning diploid somatic cells into haploid gametes 11-4 Meiosis Process of turning diploid somatic cells into haploid gametes Must reduce chromosome number so when fertilization takes place we re-establish the regular chromosome number Humans Hapolid – sex cells N = 23 Diploid – somatic cells 2N = 46 N = chromosome number

Phases of meiosis Meiosis I and II

Figure 11-15 Meiosis Section 11-4 Meiosis I

Figure 11-15 Meiosis Section 11-4 Meiosis I Meiosis I

Figure 11-15 Meiosis Section 11-4 Meiosis I Meiosis I

Figure 11-15 Meiosis Section 11-4 Meiosis I

Figure 11-15 Meiosis Section 11-4 Meiosis I

Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II Metaphase II Anaphase II Telophase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells.

Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II Metaphase II Anaphase II Telophase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells.

Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II Metaphase II Anaphase II Telophase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells.

Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II Metaphase II Anaphase II Telophase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells.

Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II Metaphase II Anaphase II Telophase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells.

Crossing over Parts of chromosomes “switch places” Meiosis

Crossing-Over Section 11-4

Crossing-Over Section 11-4

Crossing-Over Section 11-4

Mitosis vs. meiosis

11–5 Linkage and Gene Maps A. Gene Linkage B. Gene Maps Section Outline Section 11-5 11–5 Linkage and Gene Maps A. Gene Linkage B. Gene Maps

11-5: Linkage and Gene Maps Found that some genes were linked to other ones Seems to violate the rule of independent assortment Ex: fruit flies – red eyes and minature wings

Mendel missed this…. He thought the genes independently assorted Actually it was the chromosomes that do! Why did he miss it? 6 of the 7 genes he studied in peas were on separate chromosomes The two that were on the same chromosome were so far apart they independently assorted

Gene Map Do two genes on the same chromosome mean they are forever linked? No! Crossing over may put them on separate chromosomes The further apart genes are the more likely they could be separated during meiosis Low rate of separation and then recombination means genes are close to one another.

Figure 11-19 Gene Map of the Fruit Fly Section 11-5 Exact location on chromosomes Chromosome 2