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GENETICS: Introduction Terminology: gene allele homozygous heterozygous recessive dominant genotype phenotype Practice Problems Set 1: 1. For each of the following genotypes, give all genetically different gametes, noting the proportion of each for the individual. a. b. c. d. 2. WW Ww Tt TT For each of following, state whether a genotype or a gamete is represented. a. b. c. D GG P GENETICS INTRODUCTION: BIOLOGY Page 1 of 27 Pages More Terminolgy: Gregor Mendel Mendelian Genetics Monohybrid Cross P generation F1 (filial) generation (filial = "pertaining to offspring") Punnett square Complete Dominance I. ____________________ ____________________ (early ______'s) Austrian monk Provided basis for modern genetics, worked with ____________ plants, (Pisum), carefully designed his experiments, and gathered mathematical data) A. B. A cross of two parents for __________ trait is a _______________________ cross. 1. original parents are the ______ generation. 2. first generation offspring are the _____ (__________) generation A ____________________ ____________________ is a simple method to calculate the results of a monohybrid cross. 1. Example, EE, Ee, and ee: UNATTACHED EARLOBES ARE A DOMINANT TRAIT ATTACHED EARLOBES ARE A RECESSIVE TRAIT GENETICS INTRODUCTION: BIOLOGY Page 2 of 27 Pages 1a 1b 2a 2c 2b 2d Use the diagram above For each BOX/LETTER , LIST the PHENOTYPE (from top to bottom) 1, List the Phenotype of the P generation (the two parents) (there are two) 2. In each of the 4 boxes, list the Phenotype of each of the 4 offspring. 3. Once you have written down the PHENOTYPES of all 6 individuals, go back, and next to each phenotype, write the GENOTYPE. GENETICS INTRODUCTION: BIOLOGY Page 3 of 27 Pages 2. Use a Punnett square to calculate the following results: Red flower = RR, Rr White flower = rr a. Homozygous Dominant X Homozygous Dominant b. Homozygous Dominant X Homozygous recessive c. Homozygous Dominant X Heterozygous d. Heterozygous X Heterozygous e. Heterozygous X Homozygous recessive f. Homozygous recessive X Homozygous recessive GENETICS INTRODUCTION: BIOLOGY Page 4 of 27 Pages Practice Problem Set 2 Use a Punnett square to help solve the following: 1. In rabbits, if B = dominant black allele and b = recessive white allele, which of these genotypes could a white rabbit have? (Bb BB bb) 2. In horses, trotter (T) is dominant over pacer (t). A trotter is mated to a pacer, and the offspring is a pacer. Give the genotype of all horses. GENETICS INTRODUCTION: BIOLOGY Page 5 of 27 Pages 3. In humans, freckles is dominant over no freckles. A man with freckles reproduces with a woman with freckles, but the children have no freckles. What chance did each child have for freckles? 4. In pea plants, yellow seed color is dominant over green seed color. Give the genotype of all plants that could possibly produce green peas when crossed with an individual that is heterozygous (Y) = yellow, (y) = green GENETICS INTRODUCTION: BIOLOGY Page 6 of 27 Pages How to work Mendelian Genetics Problems 1. Write a Phenotypic/Genotypic KEY of information available BEFORE you start working the problem: (Use allele letter given to you, for this example, will use “A” and eye color, monohybrid cross, complete dominance) Genotype Phenotype __ __ = _______________ (Example): AA = Brown eyes __ __ = _______________ Aa = Brown eyes __ __ = _______________ aa = Blue eyes Write down “CROSS” with what information you have been given before you try to solve problem. 2. Male Female P1 = __ __ (__________) X genotype phenotype __ __ (__________) genotype phenotype THEN: F1 = (write down genotype and phenotype of any offspring given in problem) 3. Construct Punnet Square, (if applicable) plug in known values, compute blank squares. 4. Calculate genotypic and phenotypic % and ratios from information in filled out punnet square 5. Answer any questions from problem. GENETICS INTRODUCTION: BIOLOGY Page 7 of 27 Pages For those of you that desire additional information/assistance/practice with Mendalian Genetic Problems on the WEB, here ya go: Go to Google, type in: PUNNETT SQUARE Here are some of the hits that I looked at that seem very good/helpful: (there are more) http://www.accessexcellence.org/AE/AEPC/WWC/1994/punnett.html http://www.athro.com/evo/gen/punexam.html http://curriculum.calstatela.edu/courses/builders/lessons/less/les4/casino/ca s1ck.html http://anthro.palomar.edu/mendel/mendel_2.htm http://biology.clc.uc.edu/courses/bio105/geneprob.htm http://www2.edc.org/weblabs/Punnett/punnettsquares.html ------------------------------------------------------------------------------------------------------------- Monohybrid Crosses-Complete DominancePRACTICE DIRECTIONS: Construct a KEY, write the P and F1 generations, and, if applicable, fill out a punnet square. 1. In mice, brown hair, (B) is dominant over white hair (b). A brown mouse is repeatedly mated with a white mouse, and all of their offspring are brown. If two of these brown offspring are mated, what fraction of the F2 will be brown? GENETICS INTRODUCTION: BIOLOGY Page 8 of 27 Pages 2. How could you determine the genotype of the brown F2 mice in problem 1? How would you know whether a brown mouse is homozygous? Heterozygous? 3. Tim and Carolyn both have freckles. (Freckles F dominant over no freckles f). Their son Michael has no freckles. Show with a punett square how this is possible. What is the chance of Tim and Carolyn’s next child of having freckles? 4. Both Tim and Carolyn have a Widow’s peak hairline, but son Michael has a straight hairline, (homozygous recessive ww). What are all three genotypes for these 3 individuals? What is the chance that Tim and Carolyn’s next child will have a straight hairline? GENETICS INTRODUCTION: BIOLOGY Page 9 of 27 Pages II. Monohybrid Crosss: Incomplete Dominance A. First Example: Snap Dragons 1. KEY 2. Red X White 3. Pink X Pink GENETICS INTRODUCTION: BIOLOGY Page 10 of 27 Pages Monohybrid Crosses – Incomplete Dominance DIRECTIONS: Construct a KEY, write the P and F1 generations, and, if applicable, fill out a punnet square. 1. In the flowers SNAPDRAGONS, Red flower is dominant over White flower. Flower color is an Incomplete dominance situation. The heterozygous phenotype is PINK. A red snapdragon is crossed with a white snap dragon. What are the chances that there will be white flower offspring? 2. When chickens with splashed white feathers, (recessive) are crossed with chickens with black feathers, (dominant), the offspring have slate blue feathers. If two slate blue feather chickens are crossed, what is the genotypic and phenotypic results? (give % only) 3. A splashed white feather chicken is crossed with a black feather chicken. What is the chance of offspring having black feathers? GENETICS INTRODUCTION: BIOLOGY Page 11 of 27 Pages 4. A red snapdragon flower is crossed with a pink snapdragon flower. What are the chances that the F1 will be white flowers? 5. In # 4 above, what are the chances that the F1 will be pink flowers? 6. In # 4 above, what are the chances that the F1 will be red flowers? GENETICS INTRODUCTION: BIOLOGY Page 12 of 27 Pages Betta Genetics Betta genetics can be very complicated or very simple depending on what we look at. Before I attempt to explain any genetics however there are a few general (very oversimplified) laws of heredity you should know. To begin with, for each characteristics every organism inherits two genes, one from their mother and one from their father. Bettas are made up of millions of these gene pairs. An organism's genetic make-up is called it's genotype. Basically, these gene pairs are what determine an organisms physical appearance. The physical appearance of an organism is referred to as it's phenotype. Each characteristic generally has a recessive and dominate form of a gene. When there are two different forms of a gene the forms are called alleles (i.e.: the dominant allele and the recessive allele). If an allele, in a pair of genes, is dominant, the dominant copy overrides a recessive copy. The only way a recessive gene is expressed is if there are two copies of it. An organism with two same copies of a gene (either dominant, dominant or recessive, recessive) is referred to as homozygous. When two homozygous organisms are crossed their offspring are all homozygous for that trait. An organism with two different copies of a gene (dominant, recessive) is call heterozygous. When two heterozygous organisms are crossed half of their offspring is heterozygous and half is homozygous. Confused yet? Don't worry - you will catch on! Lets begin with a simple dominant/recessive gene - the gene that make a Betta either a single tail or a double tail. In Bettas, a single tail is dominant to a double tail. This is a double tail Betta - notice the tail is split into two lobes. His alleles are d, d This is a single tail Betta - his tail is only one lobe. His alleles could be D, D, or D, d Relationships between genotype and phenotype Alleles Genotype Phenotype D D D d Homozygous Dominant Heterozygous Single tail d d Homozygous Recessive Single tail GENETICS INTRODUCTION: BIOLOGY Page 13 of 27 Pages Double tail Genetics Worksheet-Betta Crazed DIRECTIONS: For each problem, 1st make key, then write the P generation, then punnet square, then phenotypic and genotypic results. (Give both % and ratio) (All problems are either Complete Dominance or Incomplete Dominance) (HINT: Complete Dominance problems have two phenotypes, Incomplete Dominance have 3 phenotypes) Before you start with Question 1, Please read the Article: “BETTA CRAZED” (Use the information in the article to answer questions 1 - 8) (Use a separate sheet of notebook paper to work these out.) 1. Two double tailed Bettas are crossed. Determine the genotypic and phenotypic results. 2. Two Homozygous dominant Bettas are crossed. Determine genotypic and phenotypic results. 3. Two Heterozygous Bettas are crossed. Determine the genotypic and phenotypic results. 4. A double tailed Betta is crossed with a single tailed, Homozygous Dominant, Betta. Determine the genotypic and phenotypic results. GENETICS INTRODUCTION: BIOLOGY Page 14 of 27 Pages 5. Two of the F2 in number 4 above are crossed. Determine the phenotypic and genotypic results. 6. Have these problems been Complete Dominance, or Incomplete Dominance Problems so far? Why? (explain your answer) 7. In Bettas, Green body color, (G), is dominant over Blue Body Color, (g). For Heterozygous individuals, the phenotype is cornflower blue. Two heterozygous cornflower blue Bettas are crossed. What are the chances for Green F1? 8. Is question #7 a Complete Dominance, or Incomplete Dominance problem? Why? (explain your answer) GENETICS INTRODUCTION: BIOLOGY Page 15 of 27 Pages III. Dihybrid Cross (Complete Dominance) A. EXAMPLES: DIHYBRID CROSS GENETIC Practice PROBLEMS # 1 1. Both T (tall) and H (hairy) are completely dominant over short (t) and bald (h). If a heterozygous tall, homozygous hairy male fox bug is mated with a female which is heterozygous tall and heterozygous hairy: a. What is the genotype for the male? _____ _____ b. What is the genotype for the female? ____ ____ a. Fill in the Punnett Square below and predict the number of expected phenotypes of fox bug offspring. GENETICS INTRODUCTION: BIOLOGY Page 16 of 27 Pages 2. In watermelons, the genes for green color (G) is dominant over striped (g) and short shape (S) is dominant over long shape (s). a. If a plant with long, striped fruit is crossed with a plant which is heterozygous for the traits of color and shape, What are the genotypes for the two parent plants? Long striped: _____ _____ Heterozygous: _____ _____ b. What phenotypes would this cross produce? GENETICS INTRODUCTION: BIOLOGY Page 17 of 27 Pages 3. In rabbits, spotted coat (S) is dominant to solid color (s), and black (B) is dominant to brown (b). a. If a brown spotted rabbits are mated to solid black rabbits and all of the offspring are black spotted rabbits, what must the genotypes of the offspring and parent rabbits be? Males: _____ _____ Females: _____ _____ Offspring: _____ _____ a. If two of the second-generation black spotted offspring were mated, what would the phenotypes of the third generation be? GENETICS INTRODUCTION: BIOLOGY Page 18 of 27 Pages Dihybrid Crosses-GENETIC PROBLEMS 2 1. In the garden pea, Mendel found that yellow seed color was dominant to green and round seed shape was dominant to shrunken. Determine the phenotypic and genotypic ratios for the F1 generation and the phenotypic ratio for the F2 if a plant with homozygous rounded yellow seeds is crossed with a plant with shrunken green seeds. (Y = yellow, y = green, R = round, r = shrunken) Show Punnett Squares. 2. Tall tomato plants are produced by the action of a dominant allele T and dwarf plants by its recessive allele t. Hairy stems are produced by a dominant gene H and hairless stems by its recessive allele h. A dihybrid tall, hairy plant is crossed with a dwarf hairless tomato plant. Determine the phenotypic ratio for the F1 generation. Show work. (Punnett Square). 3. Black coat color in Cocker Spaniels is dominant, while red coat color is recessive; solid pattern is dominant, while spotted pattern is recessive. A solid black male is mated to a solid red female and produces a litter of six pups: two solid black, two solid red, one black and white, and one red and white. Determine the genotypes of the parents. (B = black coat, b = red coat, S = solid pattern, s = spotted pattern) Show work. GENETICS INTRODUCTION: BIOLOGY Page 19 of 27 Pages 4. In rabbits, black color is due to the dominant gene B and brown color is due to its recessive allele b. Short hair is due to the dominant gene S and long hair to its recessive allele s. In a cross between a heterozygous black short-hair male and a homozygous brown long-hair female, what would be the expected genotype and phenotype ratios of the offspring? Show work. 5. In horses, black coat color is determined by a dominant gene B and chestnut brown color by its recessive allele b. The trotting gait is due to the dominant gene T and the pacing gait is due to its recessive allele t. If a homozygous black pacer is mated to a homozygous chestnut trotter, what will be the phenotypes and genotypes of the offspring? If two of these F1 individuals were mated, what phenotypes and genotypes of offspring could they have? (Include ratios for both genotypes and phenotypes in both generations.) GENETICS INTRODUCTION: BIOLOGY Page 20 of 27 Pages Common Crosses Involving Complete Dominance EXAMPLES: Phenotypic Ratios Tt X Tt = 3:1 (dominant to recessive) Tt X tt = 1:1 (dominant to recessive) TtYy X TtYy = 9:3:3:1 (9 dominant, 3 mixed, 3 mixed vice versa, 1 recessive) TtYy X ttyy = 1:1:1:1 (all possible combinations in equal number) GENETICS INTRODUCTION: BIOLOGY Page 21 of 27 Pages IV. Sex Linked (“X” Linked) A. First Example = Color Blindness 1. KEY 2. Examples GENETICS INTRODUCTION: BIOLOGY Page 22 of 27 Pages Genetics Worksheet – Sex Linked #1 DIRECTIONS: For each problem, 1st make key, then write the P generation, then punnet square, then phenotypic and genotypic results. (Give %). 1. (Look in your notebook for a sex-linked color blindness KEY – copy that key down for each color blind problem) (Questions 3 & 4) John, who is color blind, marries a carrier, normal vision girl, Mary. b. What are the chances for color blind children? c. What are the chances for color blind boys? d. What are the chances for color blind girls? e. What are the chances for normal vision children? f. What are the chances for normal vision boys? g. What are the chances for normal vision girls? 2. Bobby is a Color blind boy. Which parent, (FROM QUESTION 1 above), (John or Mary, or both, or neither), passed him the allele(s) for his color blindness? Explain your answer. GENETICS INTRODUCTION: BIOLOGY Page 23 of 27 Pages Genetics Worksheet –Sex Linked #2 DIRECTIONS: For each problem, 1st make key, then write the P generation, then punnet square, then phenotypic and genotypic results. (Give %). (you will only need to do one punnet square, and one phenotypic and genotypic results, since questions 2 & 3 are a continuation of question 1) Hemophilia is a sex-linked recessive human affliction. Hemophilia A is caused by the absence or minimal presence of a particular clotting factor called factor VIII. Hemophilia is called the bleeder's disease because the affected person's blood does not clot. Not only do hemophiliacs bleed externally after an injury, they also suffer from internal bleeding, particularly around joints. At the turn of the century, hemophilia was common in the royal families of Europe, and all of the affected males could trace their ancestry to Queen Victoria of England. Because none of the queen's ancestor or relatives were affected, it seems that the RECESSIVE allele she carried arose by mutation either in Queen Victoria or one of her parents. Her daughters Alice and Beatrice were carriers and introduced the allele into the ruling houses of Russia and Spain. Alexis, the last heir to the Russian throne before the Russian Revolution, was a hemophiliac. The current British royal family has no hemophiliacs because Victoria's eldest son, King Edward VII, did not receive the allele and therefore could not pass it on to any of his descendants. 1. A hemophiliac man reproduces with a homozygous normal woman. What are the chances that their sons will be hemophiliacs? 2. In Question Number 1 above, what is the chance that their daughters will be hemophiliacs? 3. In Question number 1 above, what is the chance that their daughters will be carriers (= they carry the damaging allele, but their phenotype is normal) GENETICS INTRODUCTION: BIOLOGY Page 24 of 27 Pages V. Multiple Allelles and Co-dominance A. First Example: Human Blood Type 1. KEY 2. Examples GENETICS INTRODUCTION: BIOLOGY Page 25 of 27 Pages Genetics Review: (Multiple Alleles, X-Linked) DIRECTIONS: For each problem, (when appropriate) 1st make key, then write the P generation, then Punnet square, then phenotypic and genotypic results. (Give %). (when applicable) 1. A man of blood type A and a woman of blood type B produce a child of type O. If the couple were to have many more children, what are the possible blood types possible in the offspring? 2. A woman is color blind. What are the chances of her daughters being color blind if she marries a man with normal vision? 3. From the following blood types, determine which baby belongs to which parents: (All the parents are monogamous and faithful) Mrs. Lily Munster Type A Mr. Brady Type A Mr. Herman Munster Type B Mrs. Brady Type AB Baby 1 = Type O Baby 2 = Type B 4. Mary, who is blood type AB, marries John, who is Blood type O. What are the genotypic and phenotypic outcomes of all possible offspring? 5. A Hemophiliac man marries a carrier female. What are the chances that their 1st child will be hemophiliac? 6. What are the chances that (question 5), their 1st son will be normal? 7. What are the chances that, (question 5), their 1st son will be hemophiliac? 8. What are the chances that, (question 5), their 1st daughter will be hemophiliac? GENETICS INTRODUCTION: BIOLOGY Page 26 of 27 Pages Genetics PRE EXAM Review Practice Problems DIRECTIONS: For each problem, 1st make a KEY, then write the P generation, then punnet square, then phenotypic and Genotypic results. (Give both % and ratio) 1. In Snapdragons, Red is dominant over white flowers. The heterozygote is Pink Flower. A Red flower snapdragon is crossed with a white snapdragon flower. Give Genotypic and Phenotypic results in % . (HINT – see Key in Notes) 2. In Humans, color blindness is a recessive, sex-linked trait. Jenny, daughter of Tom and Mary, is a normal visioned CARRIER. What are the genotypes of her parents, Tom and Mary? (Tom is normal visioned, and Mary is normal visioned). (HINT – see Key in Science Notebook) 3. Jenny, mentioned above, marries a color blind gentleman named Larry. What is the genotypic and phenotypic results of this cross? (Give %) 4. What are the chances of any of the offspring having normal vision? 5. Hemophilia is a recessive, sex-linked condition in Humans. Two hemophiliacs who marry cross. Give genotypic and phenotypic results. (Give%) 6. In question # 5 above, what are the chances of any of the offspring being Normal, (non-Hemophilia)? 7. Muscular Dystrophy, as the name implies, is characterized by a wasting away of the muscles. The most common form, Duchenne muscular dystrophy, is an X-linked (sex-linked) recessive disorder that occurs in about one in 5,000 live male births. Symptoms, such as waddling gait, toe walking, frequent falls, and difficulty in rising may appear as soon as the child start to walk. Muscle weakness intensifies until the individual is confined to a wheelchair. The condition also affects the muscles that allow us to breathe and the heart; death usually occurs during the teenage years, therefore, affect males are rarely fathers. The recessive allele remains in the population by passage from carrier mother to carrier daughter. Use D and d for your alleles. (Hint, key set up just like color blindness) PROBLEM (Number 7): A son with Duchenne muscular dystrophy is born to a couple who both appear to be normal. What are the chances that any child born to this couple will have Duchenne muscular dystrophy? 8. In cats, S = short hair, s = long hair; Xc = yellow coat, XC = black coat, XCXc = tortoiseshell (calico) coat. If a homozygous long haired yellow male is crossed with a tortoiseshell (calico) female homozygous for short hair, what are the expected phenotypic results? GENETICS INTRODUCTION: BIOLOGY Page 27 of 27 Pages