Inheritance
Biology 101 Inheritance Lab Part A: Sickle cell anemia is a recessive autosomal disorder in which red blood cells are sickle cell in shape, giving rise to a variety of health concerns including body tissue damage. In order to have sickle cell anemia, however, one must possess two recessive alleles (aa) for the disease. A dominant allele (A_) will result in an individual having normal blood. Interpret the following pedigree by answering the questions below. 1. Label each individuals genotyope in this pedigree. Remember you can never know 100% for sure an individual is AA so label unknowns as A_ 2. Which individuals are female? 3. What are the possible genotypes and phenotypes of the children of individual 32 and a carrier for sickle cell anemia? Draw a Punnet square below and indicate the likelihood of each genotype and phenotype. Genotypes AA Aa aa Likelihood (as % or fraction) Phenotypes Normal Carrier Sickle Cell Likelihood (as % or fraction) Part B: Color blindness is a sex linked recessive trait found on the X chromosome. Since males are XY the allele their 1 X chromosome has determines their phenotype. Since females are XX they must have both recessive alleles to be color blind (XbXb). Thus all color blind females have a color blind father since they get one of their X chromosomes from him. Interpret the following pedigrees by answering the questions below. 4. Fill out the pedigree above by labeling each individuals genotype. Remember you can never know 100% for sure a female is XBXB so label unknowns as XBX_. You will be able to determine all males. 5. How can individual 31 have colorblindness while individual 32 does not? 6. Since individual 19 is a male and is not colorblind this means that the allele for colorblindness reentered his lineage at some point. Which individual reintroduced the allele? How do you know? 7. If individual 26 has a child with a colorblind woman what would be the possible genotypes and phenotypes? What are the probabilities for each? Draw a Punnet square to figure out the answer then draw a table similar (but not identical) to that in question 3 listing the possible genotypes/phenotypes and their probabilities. Part C: Monohybrid Cross Questions 8. A man with sickle-cell anemia has a child with someone who is a carrier for the gene. What are the possible phenotypes and genotypes of the offspring? What is the likelihood of each? (The allele for sickle-cell is recessive). Show your work with a Punnet square and list the probabilities of both genotypes and phenotypes using a similar table to that seen in question 3. 9. A man and a woman who both have brown eyes, and whose parents had brown eyes, have a child with blue eyes. How is this possible? 10. A breeder of Labrador Retrievers purchases a male Labrador with a top pedigree. She knows both the dogs parents, while black, had chocolate labs in their ancestry at some point. Assuming that black is the dominant allele, what are the possible genotypes for this dog? How could the breeder test to see which genotype her new dog has? Hint: What genotype should the female Labrador have that could produce puppies that would clue the breeder into what genotype the male Labrador has? Part D: The law of independent assortment indicates that pairs of alleles segregate independently from other alleles during gamete formation. This holds true as long as traits occur on different chromosomes. The allele for red hair is recessive so an individual must be rr to have red hair. Anyone with the dominant allele will not have red hair (blond, brown, black). On another chromosome there are alleles for hair texture. The inheritance hair texture is more complicated however. There are two alleles involved here that exhibit incomplete dominance. C= Curly hair and S = straight hair. Thus individuals that are CC have curly hair, and SS have straight hair. Heterozygotes (CS) have Wavy hair. Using this knowledge lets interpret the inheritance of multiple characters. 11. A woman with red curly hair is pregnant with a child from a straight-haired man with black hair. Assume this man is homozygous dominant for not having red hair. Draw a Punnet square and answer the questions below a. What is the probability the child will have straight non-red hair? b. What is the probability the child will have red wavy hair? c.What are the possible genotypes? 12. Nearly three decades have passed and the child from the question above is pregnant herself. Her husband (and the father) has wavy red hair. What are the possible genotypes and phenotypes their offspring might have? What is the likelihood of each? Which is the most likely hair color/texture of the child? Show your work with a Punnet square and list the probabilities of both genotypes and phenotypes using a similar table to that seen in question 3. 13. A woman with red hair and green eyes is pregnant with a child from a man with black hair and brown eyes. Assuming the man is homozygous dominant for not having red hair, but heterozygous for brown eyes, what are the possible genotypes and phenotypes of the child and what is the likely hood of each? (Note that red hair and green eyes are both recessive traits). Show your work with a Punnet square and list the probabilities of both genotypes and phenotypes using a similar table to that seen in question 3. 14. A woman who is a carrier for the autosomal blood disease sickle cell anemia, and the sex linked blood disease hemophilia is pregnant with twins (one boy and one girl). Her husband has hemophilia and is a carrier for sickle cell anemia himself. The parents are worried that the twins might inherit one, or both of the blood diseases. What is the chance that the boy will inherit each disease? Both diseases? What about the girl? Draw a Punnet Square and fill out the table below. Biological Sex of Child Male Female Likelihood of Sickle cell as % or fraction Likelihood of Hemophilia as % or fraction Likelihood of both diseases as % or fraction Part E: Some traits have multiple alleles. The ABO blood group is one such allele. The i allele is recessive and homozygous recessive people are type O blood. The IA and IB alleles are dominant. More so the IA and IB alleles exhibit codominance, meaning that both traits are expressed if an individual has both alleles (IAIB individuals are blood type AB). 15. What are the possible offspring produced by an individual that is heterozygous for A type blood and Homozygous dominant for B type blood? Show your work with a Punnet square and list the probabilities of both genotypes and phenotypes using a similar table to that seen in question 3. 16. What are the possible phenotypes and genotypes of offspring from an individual with AB blood and an individual with O blood? Show your work with a Punnet square and list the probabilities of both genotypes and phenotypes using a similar table to that seen in question 3. 17. What is the one mating combination that can produce offspring with all four blood types? Draw a Punnet square to prove your answer. Part F: Calico cats are a result of female cats inheriting an orange gene on one of their X chromosomes and a black gene on the other X chromosome. 18. Why is it incredibly rare for calico cats be males? What would the chromosome complement of a male calico cat look like? 19. A female calico cat is pregnant with kittens. The male cat that impregnated her was orange. What are the possible genotypes and phenotypes of the kittens and how likely is each? Show your work with a Punnet square and list the probabilities of both genotypes and phenotypes using a similar table to that seen in question 3.
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