WORKSHEET 4-2 : INHERITANCE PATTERNS

1. A mutation occurs in a body cell.
     A: Will it affect that individual?
     B: Will it affect any offspring produced by the affected individual?
     C: Explain (Only one explanation is needed to explain both A and B above.)

2.  A: What is a mutagen?
     B: List 3 types of mutagens.
     C: What is the advantage of using bacteria to detect mutagens rather than larger organisms such             as mice or rabbits?

3. Why do chromosomal mutations tend to have a greater affect than gene mutations on the host        individual?

4. Thomas Morgan was the first "modern" genetics researcher. He conducted his work at Columbia        University in the early 1900's.
     A: What animal did he use to conduct his research?
     B: Morgan made the first successful crude location of a gene.
          1: What gene did he locate?
          2: Where did he determine that this gene was located?

5. Morgan discovered how sex is determined in most higher animals. He also established the        vocabulary for discussing sex chromosomes.
     A: What is the "X" chromosome?
     B: What is the "Y" chromosome?
     C: Who determines the sex of a child; the father or the mother? Why?
     D: What is the genotype of a female? Of a male?
     E: If humans have 46 chromosomes, how many are autosomes?

6. In humans the gene for normal blood clotting, H, is dominant to gene for hemophilia, h. This trait is        sex-linked. A woman with normal blood clotting has four children. They are a normal son, a        hemophiliac son, and two normal daughters. The father has normal blood clotting. What is the        possible genotype of each member of the family? (Express your answers as fractions)
       (Complete a Punnett square to show how you reached your answer.)

7. To better understand linkage groups and crossing over lets study two human traits. The ability to roll        your tongue (T) is dominant over the inability to roll (t), and the dimples (D) are dominant to no        dimples (d). Lets assume that Tongue Rolling (T) & Dimples (D) are a linked and that Inability to        Roll (t) & No dimples (t) are linked.
     A: Complete a Punnett square to show the offspring from the cross of a pure dominant mother (TD)             and a pure recessive father (td).
     B: How many different genotypes of offspring should result from this cross?
     C: What ratio do you get of offspring with dominant traits vs offspring with recessive traits?
            Now let's assume that a crossing over has occurred during this mating.
     D: What two new genotypes are now possible in the offspring from this cross?
     E: When does crossing over occur in human chromosomes?

8. The following questions are concerned with research methods.
     A: Define the word "bias". Give an example of bias that is common in population sampling.
             (Hint-> Remember problems encountered doing population sampling with the tongue rolling.)
     B: Why are twins useful for studying the effects of environment on development?
     C: Would it be more proper for a researcher to do Pedigree studies to track the movement of MD             through a family, or the movement of flu through a family? Why?

9. To better understand Single-Allele traits, Polygenic traits, and Multiple-Allele traits lets study several        examples of common human traits.
     A: Single-Allele Traits:
          1: Why would a disease caused by a single-allele trait be more devastating if it is coded by a                  single dominant allele than if its coded by a recessive allele?
          2: Name a disease for a single-allele trait that is coded by a single pair of codominant alleles?
     B: Polygenic Traits:
          1: Why would polygenic traits be capable of producing more variety than a single allele trait?
          2: Name a human trait that is an example of a polygenic trait.
     C: Multiple-Allele Traits:
          1: In humans the number of alleles present for a trait depends on the total number of alleles                present in the gene pool. If the human gene pool possesses 4 varieties of alleles for hair                color (black, brown, red, and blond) then would all humans possess 4 alleles for hair color?                Explain.
          2: Name a human trait that is an example of a multiple-allele trait.
     D: Summary:
          1: Try to classify the following human traits as either single-allele traits, polygenic traits, or                multiple-allele traits.
               a: hair color                     b: tongue rolling                     c: height
          2: Which type of human traits; single-allele traits, polygenic traits, or multiple-allele traits would                allow for the greatest variety in human phenotypes?

10. A: Sex-Linked traits are traits in which the alleles appear only on the …….. chromosome.
     B: Which sex, male or female, tends to display more sex-linked diseases?
     C: Name two human traits that are examples of sex-linked traits.

11. A: In sex-influenced traits how the allele appears in the person depends on the …. of the person.
     B: Name a human trait that is an example of a sex-influenced trait.

12. A: Nondisjunction is when a pair of chromosomes fails to ………………. .
     B: When a nondisjunction occurs and an individual with one too many chromosomes is said to
            have ….…., while an individual with one too few chromosomes is said to have …….. .
     C: Name the following disorders associated with nondisjunction.
            1: XO                     2: two #21 chromosomes                     3: XXY

13. A: What do amniocentesis, ultrasound, and chorion villi sampling have in common?
     B: List at least two ways in which they are different.

CRITICAL THINKING:
14. A: Would you suspect that mutations are a natural event, or have mutations been a result of our             current life styles? Explain.
     B: Would you suspect that "Germ Cell" mutations or "Somatic" mutations would have the greater             chance of causing evolutionary changes in a species? Explain.
     C: Would you suspect that all mutations are harmful? Explain.

15. Males have a XY genotype while females have a XX genotype.
     A: Which sex has more genes?
     B: List 2 traits that males do not have 2 genes for.
     C: Do you suspect that not having 2 genes for a trait would be an advantage or a disadvantage?

16. (True or False) Crossing over only occurs in animals that reproduce using sexual reproduction.                               Explain.

17. In many cultures certain hair and eye colors tend to be common.
     A: Why do certain hair and eye colors, such as blond hair and blue eyes, tend to be inherited             together?
     B: What could cause a individual person to suddenly inherit a different combination that the             parents?

18. In cats the "X" chromosome carries genes for coat color. The allele for a yellow coat (C) is        codominant over the allele for a black coat (C').
     A: A cross between a yellow male and a black female produces three male kittens. What color are             the kittens? How do you know?
     B: Why are almost all calico (yellow + black mixed together) cats female?

19. Do each of the following chromosomal behaviors increase or decrease variety in the human        population?
          A: crossing over                                                 B: linkage groups
          C: mutations                                                      D: nondisjunction

20. Several varieties of grapes, oranges, and watermelons have been developed with an odd number
       of sets of chromosomes due to nondisjunction. These fruits are often described by geneticists
       as triploid (3n).
     A:What effect does this have on these plants?
     B:How do farmers reproduce these plants?