Study Guide - Answers

Name: ________________________ Date: _________ Biology Unit 8 Study Guide: Genetics 8-1 1. What is heredity? The passing of traits from parents to offspring 2. Who was Gregor Mendel? The first to develop rules to accurately predict patterns of heredity 3. What organism did Mendel use to perform his experiments? The pea plant 4. True/False: Mendel actually repeated the experiments of another scientist, T. A. Knight. True 5. List the three reasons that Mendel chose the pea plant. The pea plant has many traits that have two forms that are easy to tell apart Mating of the plants can be controlled Peas are small, they grow easily, mature quickly, and produce many offspring 6. A cross with one pair of contrasting traits is known as a Monohybrid cross 7. In the first step of his experiment Mendel allowed the plants to ________-________________. This was important because it produced __________ __________________ plants. This generation is known as the ___ generation. Self-pollinate, true breeding, P 8. In the second step of his experiment, Mendel _________-_______________. The offspring of the P generation are known as the ___ generation. Cross-pollinated, F1 9. In the third step of the experiment Mendel allowed the plants to ______________________________. These offspring are called the ____ generation. Cross-pollinate, F2 10. What is a ratio? How do you find a ratio? A comparison of two numbers that have the same unit. To find a ratio divide both numbers by the smaller number. 11. What was the ratio of the dominant phenotype to recessive phenotype that Mendel observed? 3 to 1 8-2 12. Finish the following statement from your notes: For each inherited trait… An individual has two copies of the gene, one from each parent. 13. What is an allele? Alternate versions of genes

Name: ________________________ Date: _________ 14. What is a dominant allele? What is a recessive allele? A dominant allele is the allele that is completely expressed. A recessive allele is not expressed when a dominant allele is present. 15. What is homozygous? What is homozygous dominant? Homozygous recessive? When the two alleles of a gene are the same in an individual. AA aa 16. What is heterozygous? When two alleles of a gene are different. Aa 17. What is genotype? The set of alleles of an individual. 18. What is phenotype? The physical appearance expressed by the alleles. 19. What is the Law of Segregation? Two alleles of a trait separate when gametes are formed. 20. What is the Law of Independent Assortment? Alleles of different genes separate independently of one another during gamete formation. 8-3 and 8-4 21. What is a Punnett Square? A diagram that predicts all the possible gamete combinations in a cross 22. If the phenotype is dominant but the genotype is unknown what type of cross would you perform? Testcross 23. What is probability? The likelihood that a specific event will occur. 24. What is a polygenic trait? When several genes influence a trait 25. What is incomplete dominance? If intermediate traits between the two parents are expressed, 26. What is codominance? When both traits are displayed. 27. When does a gene have multiple alleles? Genes with three or more alleles? 28. In cats, long hair is recessive to short hair. A true-breeding (homozygous) short-haired male is mated to a long-haired female. What will their kittens look like? All Ll; all short haired 29. Mrs. And Mr. Jones both have widow’s peaks (dominant). Their first child also has a widow’s peak, but their second child doesn’t. Mr. Jones accuses Mrs. Jones of being unfaithful to him. Is he

Name: ________________________ Date: _________ necessarily justified? Why or why not? No they could both be Ww 30. Mate a rooster that is homozygous for curly feathers with a hen that is heterozygous for straight feathers. Straight feathers are dominant to curly feathers. a. Choose one letter to represent the allele for curly feathers _______ and straight feathers __________. b. Write out the genotypes of each parent below: ______________ X _______________ c. List the gametes for each parent: _____ _____ and ____ ____ Show all work for full credit. d. What are the chances of the offspring having curly feathers? ___________. e. What are the chances of the offspring having straight feathers? _________. a. b. c. d. e.

S, s ss x Ss ss,Ss 1/2 1/2

Patterns of Heredity (8-4 cont) 31. What is a pedigree? A family history that shows how a trait is inherited over several generations. 32. What are carriers? Heterozygous individuals that don’t show symptoms of the disorder they are carrying 33. What are autosomal traits? Traits that are found on the autosomes (body chromosomes found in males and females) 34. What are sex-linked traits? Traits that appear only on the X-chromosome 35. Why are males more likely to display a sex-linked trait? Because they only have one X chromosome. 36. What is the cause of genetic disorders? Mutations

Questions 38. and 39. Refer to the following diagram.

Name: ________________________ Date: _________

37. Does Norma have a recessive allele? a. Yes b. No c. There is no way to tell. 38. How many females express the trait? a. 0 b. 2 c. 4 d. 7 39. How many males express the trait? a. 0 b. 2 c. 4 d. 7