1. Patterns of Inheritance
Chapter 9
Patterns of Inheritance

2. Concept Check
The figure diagrams one of the genetic crosses that helped Mendel form his theories of inheritance. Which process distributes the “P” allele to approximately one half of the F1 gametes and the “p” allele to the other half?
independent assortment
mitosis
meiosis
chromosome crossover
Correct Answer: c

3. Concept Check
Mendel’s principle of independent assortment holds true only for traits with genes that
are close together on homologous chromosomes (linked).
are on separate chromosomes (unlinked).
have loci far apart on homologous chromosomes.
Both b and c are correct.
Correct Answer: d

4. Concept Check
The traits studied by Mendel were mostly discrete traits with two phenotypes. Many traits such as human height vary continuously. Which of the following describes the inheritance of continuously varying traits using Mendel’s rules of inheritance?
Two or more genes interact to produce the variation in the trait apparent in the population of the organism.
Two or more alleles interact to produce the variation in the trait apparent in the population of the organism.
Mendel’s principles do not apply to continuously varying traits.
Traits with continuous variability are not influenced by heredity.
Correct Answer: a

5. Interpreting Data
Trichomes are small plant hairs. The first graph represents the distribution of trichomes along the petiole (stem) of the first true leaf in a population of Wisconsin Fast Plants (Brassica rapa). Which of the following inheritance patterns would most likely lead to results such as these?
pleiotropy
multiple alleles
incomplete dominance
polygenic inheritance
Correct Answer: d

6. Interpreting Data
Students selected the top 15% of hairy plants as parents for the second generation of plants. The results of these crosses are graphed at the right. Which of the following is a conclusion consistent with the data?
The results of the selection experiment support the hypothesis that inheritance of trichomes in Fast Plants is polygenic.
The results of the selection experiment do not support the hypothesis that inheritance of trichomes in Fast Plants is polygenic.
Correct Answer: a

7. Interpreting Data
The students decided to carry out the investigation for one more generation. Again, they selected the top 15% of the hairy plants as parents. Which of the following results would be consistent with the hypothesis that the inheritance of trichomes is polygenic?
The distribution and mean number of hairs continue to shift to the right.
The distribution narrows but the mean does not shift.
The distribution curve spreads out but the mean does not shift.
Correct Answer: a

8. Biology and Society A. B. C. D. E.
Every state screens newborn infants for certain metabolic disorders such as phenylketonuria (PKU). The March of Dimes recommends that every newborn be tested for nine different metabolic disorders as well as hearing. DNA technology has opened up several additional tests that could be run for other genetic disorders. Do you think that states should shoulder the responsibility of expanding the number of newborn screening tests to include all of the relatively common disorders?
Strongly
Agree
Strongly
Disagree A. B. C. D. E.

9. Biology and Society A. B. C. D. E.
Assume that you have a history of Huntington’s chorea in your family. (Though the disease is not common, obviously there’s a chance that for a few of you this is a very real dilemma.) Huntington’s is a fatal condition that strikes during middle age and is inherited as a dominant trait—you only need one copy of the HD allele. Today, DNA screening tests are available but currently there is no way to stop the course of the disease. Some people at risk take the test—others do not. Would you take the screening test for Huntington’s if you were at risk?
Strongly
Agree
Strongly
Disagree A. B. C. D. E.

10. Biology and Society A. B. C. D. E.
Early in the history of genetics a movement developed known as eugenics. The goal of eugenics was to “breed” a better human race by using social pressures to encourage reproduction for those with “good” genes and discourage those with “bad” genes. Eugenics led to bad legislation in the United States and eventually was used by the Nazis in Europe to justify many of their atrocities. Today, genetic research is providing ever-greater detail into the workings of each and every one of us, including genetic influences on behavior and personality. For some this is an opportunity to fully realize our individual potentials; for others this research dredges up memories of eugenics. As a member of society, do you think it is important to heed the lessons to be learned from eugenics as we explore more deeply into the genetics of human beings?
Strongly
Agree
Strongly
Disagree A. B. C. D. E.