Mendel Packet - Genes

Punnett Squares are tools used by geneticists (and you!) to predict the outcome of offspring. In this packet you will be practicing predicting the outcome of offspring through different inheritance patterns using punnett squares and probability practice. I. Probability Review Probability is the likelihood that an event will happen. For example: A quarter has 2 sides (heads and tails). If you flip a quarter one time, your probability or your chance of landing on heads is ½. This is because you have two possible outcomes, heads or tails, but can only land on one. II. Practicing with Vocabulary 1. First let’s review some vocabulary words by defining them: a. Phenotype: b. Genotype: c. Heterozygous: d. Homozygous: e. Purebred: f. Hybrid: h. p generation: i. f generation: 2. For each genotype, indicate whether it is heterozygous (He) or homozygous (Ho). AA _______ Ee ________ Ii ________ Bb _______ ff ________ Jj _______ Cc _______ GG _______ Mm _______ nn ________ kk_______ OO _______ 3. For each of the genotypes below, determine the phenotype. Purple flowers are dominant to white flowers. Brown eyes are dominant to blue eyes. PP _______________________________ BB __________________________ Pp _______________________________ Bb __________________________ pp _______________________________ bb __________________________ 4. For each phenotype, list the genotypes. (remember to use the letter of the dominant trait) Strait hair is dominant to curly. Pointed heads are dominant to round heads. __________ straight __________ pointed __________ straight __________ pointed __________ curly __________ round III. Practice with basic punnett squares; Simple Dominance and Recessiveness 1. Round seeds are dominant to wrinkled seeds in pea plants. Cross a heterozygous round seeded pea plant with a wrinkled seed pea plant. a. Identify Alleles: b. Parent Cross: c. F1 genotypes: d. F1 phenotypes: 2. In dogs, the allele for long fur is dominant and the allele for short fur is recessive. Cross a homozygous dominant dog with a dog with short fur. a. Identify Alleles: b. Parent Cross: c. F1 genotypes: d. F1 phenotypes: 3. In green monsters, three tails is recessive to two tails. Cross a homozygous two tailed monster with a heterozygous two tailed monster. a. Identify Alleles: b. Parent Cross: c. F1 genotypes: d. F1 phenotypes: 4. If one parent is homozygous dominant for widow’s peak and the other is heterozygous, what are the possible combinations of their children? a. Identify Alleles: b. Parent Cross: c. F1 genotypes: d. F1 phenotypes: IV. Incomplete Dominance and Codominance Problems 1. Coat color in mice is incompletely dominant. Yellow and white-colored mice are homozygous, while cream-colored mice are heterozygous. If two cream colored mice mate, what phenotypic ratio can we expect of their offspring? a. Identify Alleles: b. Parent Cross: c. F1 genotypes: d. F1 phenotypes: 2. In snap dragons, flower color is controlled by incomplete dominance. The two alleles are red (R) and white (W). The heterozygous genotype is expressed as pink. Cross a pink snap dragon with a white snap dragon. a. Identify Alleles: b. Parent Cross: c. F1 genotypes: d. F1 phenotypes: 3. Human blood types are determined by genes that follow the CODOMIANCE patter of inheritance. There are two dominant alleles (A and B) and one recessive allele (O). Cross a woman with type AB blood and a man with heterozygous type B blood. a. Identify Alleles: b. Parent Cross: c. F1 genotypes: d. F1 phenotypes: 4. Two parents think their baby was switched at the hospital. It is 1968, so DNA fingerprinting technology does not exist yet. The mother has type O blood, the father has Type AB blood. And the baby has blood type B. a. Mothers genotype: ________ b. Fathers genotype: ________ c. Baby’s genotype: _______ or _______ d. Punnett square showing all possible genotypes for children produced by this couple e. Was the baby switched? 5. Based on the information in this table, which men could not be the father of the baby? Justify your answer with a punnett square. Name Blood Type Mother Type A Baby Type B Sammy the player George the sleeze The waiter Type O Type AB The cable guy Type B Type A 6. In shorthorn cattle, when a red bull (RR) is crossed with a white cow (WW), all of the offspring are roan-a spotted, red and white color. What offspring are expected from mating a roan bull and a roan cow? a. Identify Alleles: b. Parent Cross: c. F1 genotypes: d. F1 phenotypes: V. Dihybrids and Trihybrids 1. Assume that a cross was made between fruit flies of genotype AAbb and those of genotype aaBB. Give the punnett square for the expected F2 progeny types. Hint: F1 generation produces F2 generation What proportion do you expect to be: a) A_B_ : ____________ c) aaB_ : ____________ b) A_bb : ____________ d) aabb : ____________ . 2. Consider the following cross in pea plants, where smooth seed shape is dominant to wrinkled and yellow seed color is dominant to green. A plant with smooth, yellow seeds is crossed to a plant with wrinkled, green seeds. The peas produced by the offspring were all smooth and yellow. What are the genotypes of the parents? What are the genotypes of the offspring? Use a dihybrid cross to show prove your answer. 3. The genotype of F1 individuals in a tetrahybrid cross is AaBbCcDd. Assuming independent assortment of these four genes, what are the probabilities that F2 offspring would have the following genotypes? a. aabbccdd b. AaBbCcDd c. AABBCCDD d. AaBbccDd e. AaBBCCdd VI. Sex Linked Traits A female has the chromosomes XX, while a male has the chromosomes XY. In sexLlnked inheritance the genes are carried on the X chromosome as a rule and are usually recessive. For example: a woman with a normal gene on one X chromosome will not be colorblind, but is called a carrier for colorblindness. In order to be colorblind, a woman must carry the recessive allele for colorblindness on each of her X chromosomes. A male is either normal or has colorblindness. A male cannot be a carrier; he is either affected or healthy. 1. The gene for colorblindness is carried on the X chromosome and is recessive. A man, whose father was colorblind, has a colorblind daughter. a) Is this man colorblind? How do you know? b) Where did he get his gene for colorblindness? c) Must the fathers of all colorblind daughters be colorblind? Why? 2. A man whose parents were normal with respect for color vision marries a woman of normal vision and a similar family background. One of their daughters is colorblind. Give the genotypes of this daughter, her parents. Is the girl’s father colorblind? a. Identify Alleles: b. Parent Cross: c. F1 genotypes: d. F1 phenotypes: 3. Hemophilia is inherited exactly like colorblindness. The dominant allele calls for normal clotting time of the blood; the recessive for hemophilia. A normal woman marries a normal man. They have one daughter and 14 sons, all normal. In view of this, what gene combination would this woman most likely have? Why do you say this? What is most likely the genotype of the daughter? 4. A man whose father was a hemophiliac, but whose own blood clotting time is normal, marries a normal woman with no record of hemophilia in her ancestry. What is the chance of hemophilia in their children? 5. Cross female who is a carrier for colorblindness and a male who has normal vision. a. Identify Alleles: b. Parent Cross: c. F1 genotypes: d. F1 phenotypes: In alley cats, the coat color is determined by a gene carried on the X chromosome. Females: Xb Xb - Yellow XB Xb -Calico XBXB - Black Males: XbY - Yellow XBY - Black 6. A female calico cat is mated with a yellow male. What are the possible genotypes and phenotypes of their offspring? a. Identify Alleles: b. Parent Cross: c. F1 genotypes: d. F1 phenotypes: