Homework #2 Genetics Practice Problems: Name:______

Homework #2 Genetics Practice Problems: Name:______

<p> Homework #2 Genetics practice problems: Name:______****Remember to ALWAYS: 1. list alleles and traits for each problem ex: B=Black b=brown 2. list parental genotype 3. list possible gametes Part 1: Monohybrid crosses</p><p>1. In humans, free earlobes (F) is dominant over attached earlobes (f). If one parent is dominant for free earlobes, while the other has attached earlobes can they produce any children with attached earlobes? Parent phenotype______Parent genotypes______Gametes______Punnett Answer?______</p><p>2. In humans widow's peak (W) is dominant over straight hairline (w). A heterozygous man for this trait marries a woman who is also heterozygous. parent genotype______gametes______</p><p>List possible genoty pes of their offspring.</p><p>List the phenotypic ratio for their children.</p><p>3. In guinea pigs, the allele for short hair is dominant. What genotype would a heterozygous short haired guinea pig have? ______What genotype would a purebreeding short haired guinea pig have? ______What genotype would a long haired guinea pig have? ______</p><p>4. Show the cross for a pure breeding short haired guinea pig and a long haired guinea pig. Parent genotype______Gametes______</p><p>What percentage of the offspring will have short hair? ______</p><p>5. Show the cross for two heterozygous guinea pigs. Parent genotype:______Gametes______</p><p>What percentage of the offspring will have short hair? _____ What percentage of the offspring will have long hair? ______</p><p>Part 2: Working Backwards to determine Parental Genotypes: Some times we only know about the offspring and we want to learn about the parents. If you have been paying attention, you should have started to notice a pattern. For example, when both parents are heterozygous the phenotypic ratio always comes out 3 to 1. If one parent is homozygous recessive and the other is heterozygous, the phenotypic ratio always comes out 1 to1. Keeping this in mind see if you can solve the next two problems.</p><p>6. A male tall pea plant is crossed with a female short pea plant. The resulting phenotype ratio is 1 tall: 1 short. Tall (T) is dominant. What are the genotypes of the P1 generation?</p><p>Tall pea plant’s genotype (male): ______X Short pea plant’s genotype (female): _____ Possible gametes: ______Possible gametes: ______Show your Punnett square to prove your answer.</p><p>Genotype ratio:</p><p>Phenotype ratio:</p><p>7. A male tall pea plant is crossed with a female short pea plant. The resulting phenotype ratio is 100% tall. What are the genotypes of the P1 generation?</p><p>Tall pea plant’s genotype (male): ______X Short pea plant’s genotype (female): _____ Possible gametes: ______Possible gametes: ______Show your Punnett square to prove your answer.</p><p>Genotype ratio: </p><p>Phenotype ratio:</p><p>8. The ability to curl your tongue up on the sides (T, tongue rolling) is dominant to not being able to roll your tongue. A woman who can roll her tongue marries a man who cannot. Their first child has his father's phenotype. What are the genotypes of the mother, father, and child?</p><p>Possible female genotypes______Possible male genotypes ______</p><p>Actual genotype of female______Actual genotype of male______</p><p>Part 3: Back Cross/Test Cross: Whenan organism has the dominant phenotype, then its genotype can be either heterozygous or homozygous dominant (you can't tell by looking at it). In order to find out we must do a test cross using an homozygous, recessive organism.</p><p>9. In Border Collies, black coat (B) is dominant to red coat (b). A breeder has a black male that has won numerous awards. The breeder would like to use the dog for breeding if he is purebred or BB. To learn this information, she testcrosses him with a red female (bb). </p><p>Perform the cross as if the black dog is homozygous dominant and then again as heterozygous. Female gametes______female gametes______Male gametes______male gametes______If any of the puppies have red coat, what was the father’s genotype?______10. Two normally pigmented parents have 10 children, two of which are albino. What are the parental genotypes? (Albinism is recessive) </p><p>Part 4 Dihybrid Crosses: 11. In humans, the gene for brown eyes (b) is dominant to the gene for blue eyes and the gene for right handedness (r) is dominant to the gene for left handedness. Cross two individuals heterozygous for both of these characteristics. male genotype______possible alleles:______female genotype______possible alleles______Dihybrid Probability can be solved by multiplying the separate probabilities for each trait. Use math to solve for the probability instead of the Dihybrid cross. </p><p>12. In mice, the ability to run normally is a dominant trait. Mice with this trait are called running mice (R). The recessive trait (r) causes mice to run in circles only. Mice with this trait are called waltzing mice. Hair color is also inherited in mice. Black hair (B) is dominant over brown hair (b). Cross a heterozygous running, heterozygous black mouse with a homozygous running, brown mouse</p><p>Parent 1 genotype=______Possible alleles:______Parent 2 genotype=______Possible alleles:______Phenotypic ratio: Genotypic ratio:</p><p>Dihybrid Probability can be solved by multiplying the separate probabilities for each trait. Use math to solve for the probability instead of the Dihybrid cross______</p><p>13. extra credit: MUST BE DONE CORRECTLY AND COMPLETELY LABELED In humans, the gene for brown eyes (b) is dominant to the gene for blue eyes and the gene for right handedness (r) is dominant to the gene for left handedness. Cross two individuals heterozygous for both of these characteristics. </p>

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