Trait Survey: Widow’s Peak

Hitch-Hiker’s Thumb

Brachydactyly (Short Stubby Fingers)

Attached vs. Free Earlobes

Mid-Digit Hair

Tongue Roller

Partner Pair Mystery Question Susan received two green birds for her birthday. Shortly after they laid eggs and when the eggs hatched one chick was white, one was blue, and one was green. In a few sentences explain how this happened.

Can we predict the future? Well, kind of. We can look at our parents and grandparents and predict certain patterns of inheritance. Is this 100% reliable? No, but it is something that we can use in determining our future and the future of our offspring.

Probability Thinking Question #1: What are the chances that a pair of expectant parents will have a boy? Thinking Question #2: What are the chances that they will have two boys in a row? Thinking Question #3: How about 5 boys in a row?

Probability Principle of Probability: The number of times an event occurs divided by the number of trials Probability is identified as percent, fraction, or ratio 50% ½ 1:2

Probability: Coin Flip Example – Coin Flip 50% chance of getting heads Could get heads 10 consecutive flips Over many trials results will be near 50% Past coin flips do not affect future coin flips

Coin Flip

Pedigrees A llow us to trace family traits that result from these probabilities A pedigree is a diagram which shows several generations of family and the occurrence of certain genetic characteristics Pedigrees can be used to assess the risk of passing on a genetic disorder along with prenatal testing and genetic counseling

Mendel’s Laws of Heredity Gregor Mendel was an Austrian monk He experimented with pea plants & examined how traits are passed down through generations (Heredity) Work became foundation for the science of genetics which is the study of heredity, although initially rejected Gregor Mendel: “Father of Genetics”

Partner Pair: Thinking Question #4 Why did Mendel choose pea plants and not some other organism to study?

Traits of Pea-Plants

MENDEL’S EXPERIMENTS Mendel experimented with pea plants and looked at a variety of traits: seed color, flower color, seed shape, etc. Parental plants (P 1 ) – pure: Mendel took pure breeding plants with yellow pods and cross pollinated them with pure breeding plants with green pods.

Mendel’s Crosses: First Filial Generation (F 1 ) First Filial Generation (F 1 ): All offspring plants had green pods!!! The yellow pods had disappeared!

Second Filial Generation (F2)  Then he took these green pod plants and cross pollinated them with each other.  In every cross Mendel found that one trait in the P (parents) generation disappeared in the F1 (first filial) generation or children  The trait then reappeared in ¼ of the F2 plants (grandchildren) a ratio of 3:1

Mendel’s Pea Plants menu.htmlhttp://www2.edc.org/weblabs/Mendel/Mendel menu.html

Probability: Punnett Squares A punnett square is used to show the probability of each possible outcome from a cross. Used to find likelihood of an event, not to predict exact results of a cross. The larger the number of offspring, the closer the actual values will be to the prediction.

Thinking Question #5: Punnett Square Practice  Lets create a punnett square for his experiment shown to the right.  Thinking Question #5: A.What would the genotypes of the offspring be? B.How about phenotypes C.What is the probability that the offspring will exhibit the dominant phenotype?

Punnett Square Practice Let’s create a square to represent the cross Mendel carried out below Thinking Question #6: A. What would the genotypes and phenotypes of the offspring be? B. Which organisms would be considered heterozygous, out of the parents and offspring? C. How about homozygous? Why? D. What is the genotypic ratio

Mendel’s Conclusions: Rule of Unit Factors Each organism has factors called genes that control these traits There are different forms of each gene (alleles) Ex: 2 alleles for the gene for plant color (green and white) Thinking Question #7: What are the different alleles for the genes that control eye color? Three chromosome pairs are shown below. Lines on the chromosomes represent different alleles. Two alleles make up a gene.

Mendel’s Conclusions: Rule of Dominance When the two alleles of a pair are different, one is dominant and one is recessive -Dominant—allele that shows up (represented by a capital letter) - Recessive—allele that is hidden/masked (represented by a lower case letter) -Homozygous--(pure) both alleles of a pair are the same (YY or yy) -Heterozygous--(hybrid) alleles in a pair are different (Yy)

Mendel’s Conclusions: Law of Segregation  Every individual has two alleles of each gene  Example gene for height: 2 alleles tall (T), short (t)  When gametes are produced (sperm & egg cells) each gamete receives one of these alleles  During fertilization gametes combine (sperm & egg) and have different combination of alleles.

Mendel’s Conclusions: Law of Independent Assortment  States that genes for different traits (example seed shape, seed color, plant height) are inherited independently of one another  Example: Traits causing a plant to be tall or short might have no effect on whether its seeds are yellow or green  The (traits) separate from each other to produce different combinations in the sperm & egg cells.  ns/content/independentassortment.html ns/content/independentassortment.html

MENDEL & MEIOSIS Meiosis explains how the factors get separated independently into the gametes The factors are genes, and one gene for each trait comes from each parent. (but not all traits are controlled by only 2 genes). Not all traits are controlled by only 2 genes. We will discuss these exceptions to Mendel’s Rules.

Partner Pair: Thinking Question #8: Practice Problem In rabbits the allele for black coat color is dominant over the allele for brown coat color. Predict the results of a cross between a rabbit heterozygous for black coat color and a rabbit homozygous for brown coat color. Provide the following information: 1.Show the cross 2.Genotypic ratio 3.Phenotypic Ratio

Application Your Genetic Profile Punnett Square Practice

Di-Hybrid Crosses: Inheritance of more than one trait at a time In pea plants round (R) seeds are dominant to wrinkled seeds (r) and yellow seeds (Y) are dominant to green seeds (y) What would happen if you crossed the following: A. RRYY x rryy B. What about RrYy x RrYy? C. List the genotypic and phenotypic ratios.

Di-Hybrid Practice

Exceptions to Mendel’s Rules 1. Sex linked traits 2. Polygenic traits 3. Multiple alleles 4. Codominance 5. Incomplete dominance

Sex-Linked Traits Sex Linked Traits: traits are controlled by genes found on sex chromosomes. Typically the X chromosome is longer so it carries a lot of genes not found on the Y chromosome, Thus most sex-linked genes are X-linked recessive genes

Sex-Linked Traits Examples of X-linked traits: Hemophilia red/green colorblindness, muscular dystrophy, Thinking Question #9: Why are males more likely to express x-linked traits? Thinking Question #10: Why are females more likely to be carriers of sex-linked traits, and not actually have the disorder?

Are you Red Green Color Blind? Activity bend.com/colorblind/Ishihara.asphttp:// bend.com/colorblind/Ishihara.asp

Sex Linked Crosses: Thinking Question #11 Normal vision is represented by an X N and colorblindness is represented with X n. The Y chromosome does not influence colorblindness. 1.A male with colorblindness marries a female carrier. What is the probability that if they have a child he/she will be color blind?

Activity: Height Search

Polygenic Inheritance Some traits are controlled by more than one gene like human height, skin color, and eye color Polygenic inheritance occurs when more than one gene controls a trait. Hard to predict the outcome when more than one gene is involved.

Partner Pair: Multiple Alleles Thinking Question #12: Do you know what blood type you are? Why would this be important to know? Thinking Question #13: You are in a terrible accident and need a blood transfusion. You have type AB blood and your brother has type O. Can he give you his blood?

Multiple Alleles Human blood types are controlled by genes that have multiple alleles Type A, AB, B, O Type A alleles= I A I A or I A i Type B alleles= I B I B or I B i Type AB alleles= I A I B O = ii

Blood Types

Thinking Question #14: Let’s Do a Cross If a woman with type O blood and a man with type AB blood have children what are the children’s possible genotypes?

Mystery Activity: Blood Types

Exceptions to the Rules: Codominance One allele is not completely dominant over the other and they both show up in the phenotype. Example: In cows allele for red hair is codominant with allele for white hair. Offspring have both red and white hair (roan). RR= Red hair RW = Red & White hairs WW = White hair

Partner Pair: Thinking Question #15 Thinking Question #15: A black chicken is crossed with a white chicken. What would the offspring look like if feather color was inherited by codominance? We said that blood type was an example of multiple alleles. Could it be an example of another exception to Mendel’s rules? Why?

Codominance in Chickens

Blood Type: Codominance Blood type is also an example of codominance because both A and B alleles are dominant and both show up in the offspring.

Exceptions to the Rules: Incomplete Dominance Incomplete dominance-- neither allele is dominant, and the heterozygous offspring are somewhere between their parents Example: A flower with on red color gene and one white color gene is pink!

Partner Pair: Thinking Question #16 A flower with one red color gene and one white color gene is pink. Due to incomplete dominance neither allele is dominant. The heterozygote offspring is pink. Write the genotype of each flower: Red Flower: Pink Flower: White Flower Create a punnett square showing the cross of two pink flowers. Describe the phenotypic and genotypic ratios of offspring

Thinking Question #17 What would the offspring look like if flower color in the previous example was inherited via co dominance?

Partner Pair Mystery Question: So What About Those Eggs? Now that you are an expert on Mendelian genetics, explain in terms of inheritance what is going on in the pictures below.