Genetics Unit Test: Practice Guide Answers Part A: Complete the following questions: 1.) What is the purpose of a punnett square? What does it show? All possible results of a genetic cross. The possible genotypes of the offspring. The alleles in the gametes of each parent. 2.) What is a genotype? Genetic makeup Give an example of how it is written. GG 3.) What is a phenotype? Physical appearance Give an example of how it is written. green 4.)In a simple dominance problem involving green pea pods (green is the dominant color), what would be two possible genotypes for green pea pods? GG or Gg Why are they both green? the dominant trait is expressed phenotypically. G g 5.)In a simple dominance problem, what parental genotypes cross to produce a 3:1 phenotypic ratio of green pea pods G to yellow pea pods? Draw an example to the right. g 6.) Same punnett square as #5. Phenotypes = 3 green: 1 yellow Genotypes = 1GG:2Gg:1gg 7.) What does homozygous mean? Two of the same alleles What are two other terms meaning the same thing? pure or purebred 8.) What does heterozygous mean? Alleles are different What is one other terms meaning the same thing? Hybrid 9.) What does the Law of Segregation say? When organisms reproduce, alleles separate from each other Is there an equal chance of inheriting each allele from one parent? yes How about the other parent? each parent contributes 50% X X Draw an example punnett square using the sex chromosomes (Female = XX, Male = XY). Y X 10.)Snapdragon flowers exist in three color variations; white, red, and pink. What type of inheritance does this show? Incomplete dominance What would be the genotypes for each of the phenotypes described above? To the right, cross a Pink flower with a Pink flower, and give the genotypic and phenotypic ratios. R Red: RR, White: WW, Pink: RW R Genotypic Ratio: 1RR:2RW:1WW W W Phenotypic Ratio: 1red:2pink:1white 1 Genetics Unit Test: Practice Guide Answers 11.) What does incomplete dominance mean? Incomplete dominance involves alleles that are not clearly dominant or recessive. The third phenotype is a blending or intermediate of the other 2 pheontypes. 12.) What does co-dominance mean? Two dominant alleles that are expressed at the same time. 13.) Roan cattle have a coat that has both red and white hairs appearing at the same time. Answer the following questions using this information. a. What is this type of inheritance called? Co-dominance b. How is a Roan cow produced? What would be the genotypes of the parents that would only produce Roan calf? red and white hairs intermixed in the coat of the calf- producing red patches and white patches c. What would be the genotypes and phenotypes of the offspring of two roan cattle. Complete the punnett square to the right to solve the problem. Genotypes: _____________________________________ CR CW C R C W Phenotypes: 1 red, 2 roan, 1 white 14.) What is a karyotype? A picture of our chromosomes What can be observed in a karyotype? An extra or missing chromosome[s] 15.) What is selective breeding? Specific desirable traits are chosen to reproduce Give an example. Dogs 16.) What is genetic engineering? Taking DNA from one source & transferring it into another living thing. Give an example of how it can be beneficial for someone who is diabetic. Using plasmids to create recombinant DNA, it has made insulin cheaper and more readily available. 17.) How might GMO (genetically modified organisms) crops be harmful to humans and the environment? Genetic engineering has led to genetically modified plants that resist insect pests and bacterial and fungal infections. This could cause unplanned ecosystem interactions. 18.) What is gene therapy? specific gene sequences are inserted into an individuals cells and tissues to replace a defective or mutant allele. How does it work? Use viruses to insert specific gene sequences. 19.) What is cloning? What does the process produce? Cloning an individual usually produces organisms that contain identical genes. 2 Genetics Unit Test: Practice Guide Answers 20.) What does the Law of Independent Assortment say? Two alleles separate independently of one another. Give an example. A certain type of flower has two alleles for color (red, white), and two alleles for stem height (tall, short). 21.) What is a polygenic trait? Controlled by more than one gene. Give an example. Height 22.) What does it mean if a trait is sex-linked? The trait is on the sex chromosome What chromosome are they located on? The X chromosome only 23.) Why do men more frequently suffer from sex-linked diseases? They only have one X What does it mean for a woman to be a carrier? Woman have two X chromosomes, so one could be normal & the other could have the trait 24.) What is PKU? an inherited disorder that increases the levels of a substance called phenylalanine in the blood. How is it inherited? recessive Show a cross between two H heterozygous parents that do not have PKU. H h h Part B: Use the table to solve the following blood type problems: 25.) A Mother with type A blood has offspring with a Father with type O blood. Complete two punnett squares to find the probability that their children will have type B blood. IA IA IA i i i IA i IA i i i IA i IA i IA i i i i i IA i They will not have a child with type B blood! 26.)Blood type is inherited through multiple, codominant alleles, including IA, IB, and i. A child has type B blood. If the father has type AB blood, what are all the possible phenotypes of the mother? A, B, AB, or O 3 Genetics Unit Test: Practice Guide Answers 27.) There has been a mix-up at the hospital, and the staff is attempting to make sure that the babies have made it home with their appropriate parents. Sheryl has type A blood, AA or AO and her husband Steve has type B blood, BB or BO. Please make both appropriate punnett squares to show if their “baby” who has type O blood is definitely their baby. A O B O Part C: Use the pedigree to answer the following questions: 28.)What is a pedigree used for? Determine whether a trait is inherited. Show how a trait is passed from one generation to the next. Determine whether an allele is dominant or recessive. 29.)What do the squares represent? Males 30.)What do the circles represent? Females 31.)What does a shaded circle or square indicate? They have the trait 32.)How many generations are shown? 3 33.)How many children did the original parents have? 4 34.)How many males are there in the third generation? 5 35.)How many individuals are colorblind in this pedigree? 2 36.)How many individuals are carriers in this pedigree? 4 37.)How will you study differently for this exam? What study strategies will you use? 4