UNIT 6 Genes and Inheritance sciencepeek.com

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1 Part 1 - Inheritance of Genes Name Date Period 1. Fill in the charts below on the inheritance of genes. 2. In a diploid cell, there are copies of each chromosome present. 3. Each human diploid cell has a total of chromosomes or pairs of chromosomes. 4. A copy of a gene that can be passed from a parent is termed an. 5. We receive copy of a gene from mom and copy of a gene from dad. 6. Genes are located on. 7. How can a bad gene make you smell like rotten fish? 8. Who are carriers of fish odor syndrome above? Explain what a carrier is. 1 of 8

2 Part 2 - Single-Gene Traits 9. Define Heredity 10. The inheritance of some traits is easy to predict. When a single gene influences a trial (a single-gene trait), will the inheritance of that trait be relatively easy or difficult to predict? Justify your answer. 11. Provide an example of a human trait that would not be considered a single-gene trait. Part 3 - Mendel and Heredity 12. Gregor Mendel s work was fundamental to all modern genetic theories. There were three features of Mendel s work that were particularly important to his success. Those were: Part 4 - Mendel s Law of Segregation 14. Mendel s experiments in crossing pea plants led to predictable results. For example, crossing a - purple pea plant to a - white pea plant always led to offspring. This is because the purple color is while the white color is. 15. Mendel s hypothesis for explaining the pattern of inheritance observed in pea plants incorporated three ideas that then helped him make predictions about crosses he hadn t yet done. They are: of 8

3 16. The concept of dominance is often misunderstood. People tend to think that dominant alleles are more common than recessive alleles or that they are in some way more advantageous than recessive alleles. In your own words, describe how a dominant allele is different from a recessive allele. 17. For any given trait, an individual receives exactly two copy of a gene from each parent via the gamete. This leads to individuals whose diploid cells have exactly copies of each gene. 18. When an individual inherits two of the same allele from both parents, we call this, and when an individual inherits two different alleles from their parents, we cal this. 19. Briefly summarize Mendel s Law of Segregation. Part 5 - Genotype, Phenotype, Punnett Squares and Probability 20. Explain what the term phenotype means. 21. Explain what the term genotype means. 22. The three possible genotypes for any given trait, are: 23. Why is it sometimes impossible to know an individuals genotype based on their phenotype? Explain. 24. What is a Punnett square used for and how would you go about setting one up? 3 of 8

4 25. In the following example, there are two possible alleles for the gene that determines whether a person has dimples. Having dimples is dominant and the allele will be represented as D. Not having dimples is recessive and the allele will be repressed as d. For in the table below. Possible Allelic Combinations Genotype Phenotype DD Homozygous dominant Dd dd 26. Suppose your roommate has dimples. Can you be sure of her genotype? Explain your answer. 27. Show a Punnett square for the dimples trait between a homozygous recessive parent and a heterozygous parent. Indicate the phenotypic ratio for their offspring. 28. In this screencast you saw examples of Punnet squares using albinism in giraffes. Given the following example, fill in the gametes that would be produced by each parent, the offspring that would be produced, and the phenotypic ratio of the offspring. 29. Fill in the chart below describing probability. 30. What would be the probability of a child inheriting Tay-Sachs disease from a mother who is heterozygous for the trait and father who is homozygous dominant for the trait? 31. Explain how you would use the rules of probability to determine your answer 4 of 8

5 Part 6 - Sex-Linked Traits A sex-linked trait is carried on the X chromosome. Women carry two copies of the X chromosome, while men carry an X chromosome and a Y chromosome. 32. Fill in the chart to the right On the sex-linked trait: Color-Blindness 33. Traits that are coded for on sex chromosomes have unique patterns of inheritance. Recall that the genotype of a female is and the genotype for a male is. 34. Which gender is more likely to exhibit a sex-linked recessive trait? 35. Suppose that a female exhibits red-green colorblindness. What must the genotype of her parents have been? Explain your answer and draw a punnet square. 36. Pedigrees are useful tools for determining the pattern of inheritance for a specific allele. Females are represented by and males are represented by. 37. If a trait of interest is located on an autosome (non-sex chromosome), the pattern of inheritance will be or. 38. How is a carrier represented on a pedigree? Part 7 - Incomplete and Codominance & Polygenic Traits 39. Not all genetic traits operate by simple dominance of one allele over a recessive allele. One situation in which complete dominance is not observed is called Incomplete dominance. Describe incomplete dominance below: 40. Give some examples of incomplete dominance below and explain one. 41. Fill in the chart to the right. 5 of 8

6 42. Define codominance. 43. Explain how the picture to the right illustrates codominant inheritance. 44. Polygenic traits are ones in which a single phenotype is influenced by genes. 45. At first glance, incomplete dominance and codominance seem very similar to each other. Explain how they are different. 46. Roan cows have a interesting coat color. They have blotches of red fur and blotches of white fur. If you're told that their genotype is heterozygous, which rule of inheritance do you think applies to the development of roan coat color? Explain your answer. Part 8 - Multiple Alleles Blood Types Multiple allelism occurs when there are three or more alleles for a gene within a population. An individual still inherits only two alleles one from each parent. 47.When a single gene has more than two alleles, this is referred to as multiple allelism. Human blood type is an example. How many alleles are involved in this trait? How many alleles do you inherit for this trait? What are the alleles for blood type? 48.How does the term antigen relate to blood type? 49.A and B are completely dominant to. 50. If you have two copies of the O allele your blood type is. 51. The A and B alleles are codominant with each other, so the genotype AB gives rise to blood type. 6 of 8

7 52. In the chart below, indicate the four human blood types, the potential genotypes of each, and the antigens that would be present on the red blood cells of an individual with that specific blood type. Possible Blood Types Potential Genotypes Antigens Coded For 53. Fill in the chart below. ANTIGENS Chemicals on the surface of some cells. They act as signposts that tell the immune system whether the cell belongs in the body. ANTIBODIES Immune system molecules that attack cells with foreign antigens. 54. Antigens are: 55. Antibodies are: 56. Speaking in terms of the immune system, what would happen if a person with type A blood were to receive a type B blood transfusion? 57. In addition to the ABO markers, there is another genetic marker that determines whether an individual s blood type is positive or negative. This is referred to as the. 58. What happens when a person with Rh+ blood donates to someone with Rh- blood? FATHER pigmented heterozygous Aa dimpled chin heterozygous Dd MOTHER pigmented heterozygous Aa dimpled chin heterozygous Dd Part 9 - Independent Assortment and Gene Linkage 59. Fill in the illustration of independent assortment to right. 60. In order for independent assortment to occur, the traits must exist on separate. 7 of 8

8 61. Fill in the graphic below, illustrating gene linkage. 61. Why do most redheads have fair skin and freckles? 62. When traits are considered linked, they exist in close proximity on the same chromosome. How can meiosis be used to explain why linked traits do not assort independently from one another? Part 10 - Pleiotropy and Environmental Effects 63. It is important to note that traits are not shaped by genotype alone. The ultimate phenotype expressed is shaped by both the genes inherited in combination with the. 64. Provide three examples of human phenotypes that can be shaped by factors other than genes: Drinking diet soda can be deadly if you carry a single bad gene. What gene is it and why is it so deadly? 66. Could you create a temporarily spotted Siamese cat with an ice pack? Why? 8 of 8