Name: Block: Date: Packet #12 Unit 6: Heredity

Transcription

1 Name: Block: Date: Packet #12 Unit 6: Heredity Objectives: By the conclusion of this unit, you should be able to: Topic 1: Simple Heredity 1. Define and relate the following terms: self-fertilization, cross-fertilization, true-breeding (purebred), hybrid, P generation, F1 generation, and F2 generation. 2. Define and relate the following: genes, alleles, sister chromatids, and homologous chromosomes. 3. Describe how Mendel studied inheritance in peas including F1 and F2 breeding experiments. 4. Explain the four hypotheses that Mendel developed after his first set of experiments. Define and explain the law of dominance and the law of segregation in your answer. 5. Define and relate homozygous, heterozygous, genotype, and phenotype. 6. Use a Punnett Square to predict the outcomes (genotypic and phenotypic ratios) of one-factor crosses (Packet page 8). 7. Explain the law of independent assortment and relate it to meiosis. 8. Use a Punnett Square to predict the outcomes of two-factor crosses (Packet page 11). 9. Explain how geneticists can use a testcross to determine unknown phenotypes. 10. Explain the principle of probability and its limitations in genetics. Topic 2: Patterns of Inheritance. 11. Describe the inheritance patterns that exist aside from simple dominance, including: a. incomplete dominance. b. multiple alleles c. codominance d. pleiotropy. e. polygenic inheritance. f. sex-linked traits 1

2 12. Describe how blood types are inherited and why they must be considered when doing transfusions. 13. Identify different patterns of inheritance using a pedigree analysis. Key terms Topic 1: Topic 2: Self-fertilization Monohybrid cross Dihybrid cross Incomplete dominance Cross-fertilization Dominant allele Testcross Multiple alleles True-breeding Recessive allele Probability Codominance Hybrid Law of dominance Rule of multiplication Pleiotropy P generation Law of segregation Rule of addition Polygenic inheritance F1 Homozygous Linked genes F2 Heterozygous Sex-linked gene Genes Phenotype Pedigree Alleles Genotype Antibodies Homologous chromosomes Punnett square Nondisjunction ABO blood group 2

3 1. How to read a pedigree: Journal 7-1: Chances' Choices Paul and Stacy : 2. What is PKU? Below is a schematic of what happens in this disease. Describe the symptoms. 1. What is state-mandated testing of newborns? Give some examples of diseases tested for. 3. Describe dominant vs. recessive traits and genotypes. 3

4 Daley Biology A Explain why it makes sense that PKU is recessive (at a molecular level). 5. Do Frank and Alan have the gene for this enzyme? 6. Do Frank and Alan carry the allele that causes PKU? a. Let s review meiosis: Before After Metaphase I Interphase Interphase b. What are Paul and Stacy s genotypes? x c. Which alleles could be in Paul s sperm? or d. Which alleles could be in Stacy s eggs? or e. Using a Punnett square to make predictions: Prophase II Metaphase II Sperm cells f. What fraction of Paul and Stacy s children do we expect to have PKU? 7. What does each row or column in a Punnett square represent? 8. What does each individual box represent? Scene 2: Will Alan ever play for the Celtics? g. What are the chances of Paul and Stacy having another child with PKU? 4

5 1. What is an X-linked trait? 2. How do you indicate an X-linked trait in a genotype? 3. What is hemophilia? 4. What are the chances of Paul and Stacy have a child with hemophilia AND PKU? Parent's genotypes: x Paul Stacy Chromosomes in metaphase I of Meiosis: PAUL OR Gametes: (FOIL),,, Two-Factor/Dihybrid Cross: STACY OR,,, 5

6 So... A. What are the chances of Paul and Stacy having a child with hemophilia AND PKU? B. What are the odds of an individual child being a boy? C. What are the chances of having a girl with hemophilia? D. What are the chances of having a girl that is a carrier of hemophilia and a carrier of PKU? 6

7 Journal 7-2: Probability and Genetics Introduction: If someone flips a coin, you know that there are two possible outcomes: heads or tails. You can predict how likely either is to happen. Can you make similar predictions about the outcomes of genetic events? In this activity, you will use biological data to explore the concept of probability. Probability is a mathematical tool that enables us to make predictions. We will provide you with information about the offspring of two rabbits, and you will look for patterns in the results. This activity is an altered version of Game of Chance on page 420 of your textbook. Pre-Journal Discussion: Read the entire investigation. Then, work with a partner to answer the following questions. 1. What does a single side of a double-sided coin represent in this activity? 2. What is the probability, in percent, that a single coin toss will result in heads? In tails? 3. Why is a coin toss a good way to represent allele combinations that occur in nature? 4. Can you accurately determine an organism s genotype by observing its phenotype? Explain your answer. Materials: one penny per student 7

8 Procedure: 1. Work with your teammate to solve the following problems. a. A pair of rabbits mated and produced 10 offspring. How many males and how many females would you predict are in those offspring? (statistically not a guess) 2. Even if you are reasonably confident that your prediction is correct, can you guarantee how many males and females will be born in the litter? Explain your answer. Test your prediction by using a coin to simulate the sex of the 10 offspring. Explain the role of chance in determining your results. 3. Look at the data below these show the results of 3 rabbit matings. Small sample size Trial # of offspring Males Females a. Do these results match your predictions or test results from step 1? Heads Tails Predicted 4. Next investigate the relationship between probable outcomes, actual results, and sample size. Examine the data below. Note that the total number of offspring is 600. Calculate the percentage of male rabbits for each group of 600 offspring. Record these results in the table. (Percentage males = [(# males) / (# total offspring)] x 100) Large sample size Actual Trial # of offspring # Males # Females % Males

9 5. Answer the following questions: a. Are these results generally closer to 50 percent than those in the small sample size (step 3)? b. Based on your observation, what effect does sample size have on the match between probable outcomes and actual results? 6. Now, test the accuracy of large sample sizes by generating your own data with coins and combining the data of the entire class. a. This time, instead of flipping the coin 10 times, flip it 20 times. Then calculate the % of total flips for heads and tails. Record the results. Heads Tails b. Contribute your data to the class data table on the board and record the results. 20 flips % of total Class data % of total c. What do these results suggest about the effect of sample size on the match between probable outcomes and actual results? 9

10 Analysis and Discussion: 1. Use what you have learned about the importance of sample size to evaluate the following medical study reported in a local newspaper. A study reported in a medical journal Acta Artifacta appears to link ownership of fast cars with premature balding. The study, consisting of 17 men who own sports cars, found that nearly 70 percent suffered from premature balding. The authors of the study conclude that because this percentage of balding is much higher than in the general population, there is an increased chance of suffering from premature baldness if one owns a fast car. 2. If you flip a coin five times and get heads every time, what is the probability that you will get tails on the next flip? 3. Restate the following accurately: One out of every two offspring that results from a cross between parents with the Genotypes Hh and hh definitely will have Huntington s disease. [Hint: Huntington s disease is a dominant trait] 4. Evaluate the following claims. Who is right? Explain. Marcia I really think we should have another child. I know we already have 5 boys, but I ve always wanted a little girl. Since I ve had 5 boys already, probability says that I am overdue for a girl. I am much more likely to have a baby girl this time. Tom We have enough children already. Plus, you are no more likely to end up with a girl this time than any other time. You could end up with 6 boys and then where would we be? 10

11 Probability and Genetics Notes 11

12 Mendel and Punnett Squares Notes Mendel s life Punnett Squares - Reminders Simple Dominance 12

13 Alternate Forms of Inheritances Notes Incomplete Dominance (and an example) Codominance (and an example) Polygenic traits (and an example) There are 3 alleles for blood type:,,. The blood types (and their genotypes) are: Type A blood: or Type B blood: or Type AB blood: Type O blood: Blood type is determined by which you have on your blood cells If you are missing a certain antigen, the body develops that attack that antigen if they encounter it. Type A blood has antibodies against antigens Type B blood has antibodies against antigens Type AB blood has antibodies against antigens Type O blood has antibodies against antigens 13

14 Journal 7-3: Solving Genetics Problems When doing genetics problems, you should always: write all answers (neatly) on a separate piece of paper. Number the problems and show all work/ explain your reasoning. Mendelian Genetics you should know: Law of Segregation, Law of Dominance, Law of Independent Assortment, dominant, recessive, homozygous, heterozygous, genotype, phenotype, how to set up symbols, the meaning of a Punnett square, probability, generations: parental, F1, & F2. Monohybrid crosses: 1. Long eye-lashes are dominant over short eye-lashes. Cross a heterozygous long eye-lashed mother with a homozygous long eye-lashed father. Show the results of the cross. 2. The genetic disease called cystic fibrosis is inherited through a recessive gene. If both parents are heterozygous for this trait, what is the probability that they will have a child who suffers from this disease? 3. In mice, black fur is dominant to white fur. How would you determine whether a black mouse is homozygous dominant or heterozygous? (Hint: you will have to breed some mice). 4. A male and a female, each with free earlobes (a dominant trait), give birth to a daughter with attached earlobes (a recessive trait). a. If the couple has three more children, what is the chance that ALL of them will also have attached earlobes? b. If the couple then has one more child (the first three are already born), what is the chance that this child will also have attached earlobes? c. What is the chance that this fourth child will be a BOY with attached earlobes? Dihybrid crosses: Use the same method as above, except: ü Parental genotypes have (#) letters (corresponding to copies of each gene) ü Each parental gamete has (#) letters (corresponding to copies of each gene) You can use FOIL (First, outside, inside, last) to figure out the gametes) ü You need the same number of rows and columns have you have possible ü Each box in the square represents a possible, so should have (#) letters. You could also use multiple 2x2 Punnett squares and the rules of probability (use this if you have 3 or more traits) 5. Tongue rolling is dominant over non-tongue rolling, and brown eyes are dominant over blue. Cross a heterozygous tongue rolling, brown-eyed mom with a heterozygous, tongue rolling brown-eyed father. What are the gametes possible from each parent? What are the expected genotypes and phenotypes for the offspring? 6. Bill and Barbara both have freckles, and Barbara has a widow's peak while Bill has a straight hairline. They give birth to a daughter, Sarah, has no freckles and a straight hairline. Freckles and a widow s peak are both dominant, whereas no freckles and no widow s peak are both recessive. a. What is Bill's genotype? What is Barbara's genotype? b. What is the chance that they will give birth to a second child with freckles and a widow's peak? c. What is the chance that they will have a boy with freckles and a widow's peak? 14

15 Beyond Mendelian Genetics: you should know: chromosomes (autosome vs. sex), meiosis, carrier, pedigree, incomplete dominance, codominance (multiple alleles). X-linked traits: 7. Color blindness is inherited as a sex-linked trait where the allele for color blindness is on the X chromosome. A color blind woman becomes pregnant. Her partner is a man with normal vision. What is the probability that her child will be: a. a girl with normal vision? d. a color blind boy? b. a color blind girl? e. a girl who is a carrier for the trait? c. a boy with normal vision? 8. Hemophilia is a disease caused by a recessive gene on the X chromosome. In a family, there are the following children: 2 hemophiliac boys, a normal boy, a hemophiliac girl, and a normal girl. Draw a pedigree for this family. What must the genotypes of the parents be? What is the genotype of each child? Incomplete dominance: 9. In 4 o clock flowers, red and white color are incompletely dominant. The heterozygous condition results in pink color. You want ½ of the offspring of a cross to be pink. Give the genotypes of 3 different sets of parents to end up with that ratio in the offspring. 10. In cats, the genotype BB is black, Bb is tortoise shell, and bb is yellow. The gene is on the X chromosome. A tortoise shell female is crossed with a black male. What offspring would be expected? Would you expect to find any tortoise shell males? Explain. Codominance (multiple alleles) 11. Cross a person homozygous for blood type allele B with a person with blood type O. Show the possible genotypes and phenotypes for the offspring. 12. Use the blood type table in your notes to answer this question. What are the possible blood types of children born to the following couples? (You do not need to draw a Punnett Square for each, but be careful to consider ALL possibilities) a.) type A female, type A male c.) type A female, type O male b.) type B female, type AB male d.) type AB female, type AB male 13. Give the genotypes of everyone below. Can this couple have a child with blood type B? Explain. Type A Type B Type AB Type A Type O 15

16 1. In the animal called ipsywoodles, B=black fur F=forked tongue H=hairy body N=normal wings L=long bristles b=yellow fur f=plain tongue h=normal body n=straight wings l=short bristles If you crossed a heterozygous black furred, plain tongued, homozygous hairy bodied, heterozygous normal winged, heterozygous long bristled ipsywoodle (phew try saying that ten times fast), with the same type of ipsywoodle, how many of the offspring would have: (don t even think about trying a Punnett Square here think about an alternative problemsolving technique ) a. black fur, forked tongue, hairy body, normal wings, long bristles b. black fur, plain tongue, hairy body, normal wings, short bristles c. yellow fur, plain tongued, hairy body, straight wings, long bristles Pedigrees: 2. Draw a pedigree for a family showing two parents and four children as follows: (a) make the 2 oldest children boys and the two youngest girls. (b) label the marriage line and the children line (c) label the individuals and the generations with numbers (d) Indicate person II-2 has attached earlobes (a recessive trait) (e) Fill in the genotypes and symbols to indicate the remaining family s traits 3. Key: patterned = hanging earlobes; plain = attached earlobes a. Which is dominant and which is recessive? Explain. b. Write the genotypes of all the individuals on the pedigree below. If you cannot be sure, put what you do know about the genotype. c. What are the possibilities for the original parents genotype? d. What genetic cross term can you apply to the F1 generation male s marriage to his partner? all 25 kids 16

17 Quest Outline for Mendelian Genetics 1. What is the relationship between sample size and accuracy of prediction? 2. Explain the different causes of variation, including when they occur (mutations, independent assortment, crossing over, random fertilization). 3. Define each of Mendel s Laws (Law of Dominance, Law of Independent Assortment, Law of Segregation) and give a concrete example of each. 4. Be able to solve genetics problems, including: a. Monohybrid (2 x 2) & dihybrid (4 x 4) crosses (Honors only); probability b. Incomplete dominance & co-dominance c. Blood typing 5. What is the relationship between meiosis, fertilization, and chance of inheritance? 6. What is crossing over and when does it occur? 7. What is the relationship between genetics and environment? 8. What patterns would you see in a pedigree for a trait that is: a. Autosomal Dominant? b. Autosomal Recessive? c. Sex-linked Recessive? 9. For one disease, know the major symptoms, inheritance pattern (dominant, recessive, sexlinked, or chromosomal deletion), and one other interesting and unique fact about each. There will be a short answer question asking you to write about this Vocabulary Genotype Phenotype Allele Dominant Recessive Homozygote Heterozygote Autosome Sex chromosomes Crossing over Homologous Chromosomes 17