Chapter One: Introduction to Genetics
COMPREHENSION QUESTIONS
Section 1.1
*1. How did Hopi culture contribute to the high incidence of albinism among members of the
Hopi tribe?
Solution:
In Hopi culture, albino individuals were considered special and awarded special status in
the village. Hopi male albinos were not required to work the fields, thus avoiding extensive
exposure to sunlight that could prove damaging or deadly. Because the male albinos
remained in the village during the day, they had mating advantages over the males who
participated in farming and other duties outside of the village. Albinism was considered to
be a positive trait reflecting the purity of the villagers. Finally, the small population size of
the Hopi tribe may have helped increase the allele frequency of the albino gene due to
chance.
2. Outline some of the ways in which genetics is important to all of us.
Solution:
Genetics directly influences our lives and is fundamental to what and who we are. For
example, genes affect our appearance (e.g., eye color, height, weight, skin pigmentation,
and hair color). Our susceptibility to diseases and disorders is affected by our genetic
makeup. Genetics plays a significant role in researching and developing techniques to
diagnose and treat these hereditary diseases. Genes may also influence our intelligence and
personality. Genetic techniques have enabled scientists to develop genetically modified
crops that are resistant to pesticides and herbicides or that have enhanced nutritional
properties making it possible to produce larger quantities of food for the world’s growing
population. Lastly, genetic engineering has made it possible to mass produce
pharmaceuticals and other substances of commercial value.
3. Give at least three examples of the role of genetics in society today.
Solution:
Genetics plays important roles in the diagnosis and treatment of hereditary diseases: in
breeding plants and animals for improved production and disease resistance; and in
producing pharmaceuticals and novel crops through genetic engineering.
4. Briefly explain why genetics is crucial to modern biology.
,2 Chapter One: Introduction to Genetics
Solution:
Genetics is crucial to modern biology in that it provides unifying principles: The genetic
code is universal, meaning that all organisms use nucleic acid as their genetic material, and
all organisms encode genetic information in the same manner. The study of many other
biological disciplines, such as developmental biology, ecology, and evolutionary biology,
is supported by genetics.
5. List the three traditional subdisciplines of genetics and summarize what each covers.
Solution:
1) Transmission (classical) genetics is concerned with the inheritance of genes from one
generation to the next. It also deals with the location of genes on chromosomes and gene-
mapping. 2) Molecular genetics focuses on the structure, organization, and function of
genes at the molecular level. Molecular genetics is also concerned with the processes by
which genetic information is transferred and expressed. 3) Population genetics studies
genetic variation and changes in genes and allele frequencies within groups of individuals
of the same species over time.
6. What are some characteristics of model genetic organisms that make them useful for
genetic studies?
Solution:
Model genetic organisms have relatively short generation times, produce numerous
progeny, are amenable to laboratory manipulations, and can be maintained and propagated
inexpensively.
Section 1.2
7. When and where did agriculture first arise? What role did genetics play in the development
of the first domesticated plants and animals?
Solution:
Agriculture first arose 10,000 to 12,000 years ago in the area now referred to as the Middle
East (i.e., Turkey, Iran, Iraq, Syria, Jordan, and Israel). Early farmers selectively bred
individual wild plants or animals that had useful characteristics with others that had similar
useful traits. The farmers then selected for offspring that contained those useful features.
Early farmers did not completely understand genetics, but they clearly understood that
breeding individual plants or animals with desirable traits would lead to offspring that
contained these same traits. This selective breeding led to the development of domesticated
plants and animals.
8. Outline the notion of pangenesis and explain how it differs from the germ-plasm theory.
, Chapter One: Introduction to Genetics 3
Solution:
Pangenesis theorizes that information for creating each part of the offspring’s body
originates from each respective part of the parent’s body and is passed through the
reproductive organs to the embryo at conception. Pangenesis suggests that changes in parts
of the parent’s body may be passed to the offspring’s body. The germ-plasm theory, in
contrast, states that the reproductive cells (eggs and sperm) possess all of the information
required to make the complete body; the rest of the body contributes no information to the
next generation.
9. What does the concept of the inheritance of acquired characteristics propose and how is it
related to the notion of pangenesis?
Solution:
The theory of inheritance of acquired characteristics postulates that traits acquired during
one’s lifetime can be transmitted to offspring. It developed from pangenesis, which
postulates that information from all parts of one’s body is transmitted to the next
generation. Thus, according to the theory of inheritance of acquired characteristics, the
development of large bicep muscles through exercise would produce children with large
biceps.
10. What is preformationism? What did it have to say about how traits are inherited?
Solution:
Preformationism is the theory that the offspring results from a miniature adult that is
already preformed in the sperm or the egg. All traits would thus be inherited from only one
parent, either the father or the mother, depending on whether the homunculus (the
preformed miniature adult) resided in the sperm or the egg.
11. Define blending inheritance and contrast it with preformationism.
Solution:
The theory of blending inheritance proposes that the egg and sperm from two parents
contains material that blends upon conception, influencing the development of the
offspring. This theory indicates that the offspring is an equal blend of the two parents. In
preformationism, the offspring inherits all of its traits from one parent.
12. How did developments in botany in the seventeenth and eighteenth centuries contribute to
the rise of modern genetics?
Solution:
Botanists of the seventeenth and eighteenth centuries discovered that plants reproduce
sexually, enabling them to develop new techniques for crossing plants and creating plant
hybrids. These early experiments provided essential background work for Mendel’s plant
crosses. Mendel’s work laid the foundation for the study of modern genetics.
13. List some advances in genetics made in the twentieth century.
, 4 Chapter One: Introduction to Genetics
Solution:
1902 Proposal that genes are located on chromosomes by Walter Sutton
1910 Discovery of the first genetic mutation in a fruit fly by Thomas Hunt Morgan
1930 The foundation of population genetics by Ronald A. Fisher, John B. S. Haldane,
and Sewall Wright
1940s The use of viral and bacterial genetic systems
1953 Three-dimensional structure of DNA described by Watson and Crick
1966 Deciphering of the genetic code
1973 Recombinant DNA experiments
1977 Chemical and enzymatic methods for DNA sequencing developed by
Walter Gilbert and Frederick Sanger
1986 PCR developed by Kary Mullis
1990 Gene therapy
14. Briefly explain the contribution that each of the following persons made to the study of
genetics.
Solution:
a. Matthias Schleiden and Theodor Schwann
Proposed the concept of the cell theory, which indicated that the cell is the fundamental
unit of living organisms. Caused biologists interested in heredity to examine cell
reproduction.
b. August Weismann
Proposed the germ-plasm theory, which holds that cells in reproductive organs carry a
complete set of genetic information.
c. Gregor Mendel
First discovered the basic rules of inheritance.
d. James Watson and Francis Crick
Along with Rosalind Franklin and Maurice Wilkins, described the three-dimensional
structure of DNA.
e. Kary Mullis
Developed the polymerase chain reaction, used to quickly amplify small amounts of DNA.
Section 1.3
15. What are the two basic cell types (from a structural perspective) and how do they differ?
Solution:
The two basic cell types are prokaryotic and eukaryotic. Prokaryotic cells have neither
membrane-bound organelles nor a true nucleus. Their chromosomes are found within the
cytoplasm. Eukaryotic cells possess a membrane-bound nucleus and other membrane-
bound organelles such as an endomembrane system and mitochondria.
16. Outline the relations between genes, DNA, and chromosomes.
COMPREHENSION QUESTIONS
Section 1.1
*1. How did Hopi culture contribute to the high incidence of albinism among members of the
Hopi tribe?
Solution:
In Hopi culture, albino individuals were considered special and awarded special status in
the village. Hopi male albinos were not required to work the fields, thus avoiding extensive
exposure to sunlight that could prove damaging or deadly. Because the male albinos
remained in the village during the day, they had mating advantages over the males who
participated in farming and other duties outside of the village. Albinism was considered to
be a positive trait reflecting the purity of the villagers. Finally, the small population size of
the Hopi tribe may have helped increase the allele frequency of the albino gene due to
chance.
2. Outline some of the ways in which genetics is important to all of us.
Solution:
Genetics directly influences our lives and is fundamental to what and who we are. For
example, genes affect our appearance (e.g., eye color, height, weight, skin pigmentation,
and hair color). Our susceptibility to diseases and disorders is affected by our genetic
makeup. Genetics plays a significant role in researching and developing techniques to
diagnose and treat these hereditary diseases. Genes may also influence our intelligence and
personality. Genetic techniques have enabled scientists to develop genetically modified
crops that are resistant to pesticides and herbicides or that have enhanced nutritional
properties making it possible to produce larger quantities of food for the world’s growing
population. Lastly, genetic engineering has made it possible to mass produce
pharmaceuticals and other substances of commercial value.
3. Give at least three examples of the role of genetics in society today.
Solution:
Genetics plays important roles in the diagnosis and treatment of hereditary diseases: in
breeding plants and animals for improved production and disease resistance; and in
producing pharmaceuticals and novel crops through genetic engineering.
4. Briefly explain why genetics is crucial to modern biology.
,2 Chapter One: Introduction to Genetics
Solution:
Genetics is crucial to modern biology in that it provides unifying principles: The genetic
code is universal, meaning that all organisms use nucleic acid as their genetic material, and
all organisms encode genetic information in the same manner. The study of many other
biological disciplines, such as developmental biology, ecology, and evolutionary biology,
is supported by genetics.
5. List the three traditional subdisciplines of genetics and summarize what each covers.
Solution:
1) Transmission (classical) genetics is concerned with the inheritance of genes from one
generation to the next. It also deals with the location of genes on chromosomes and gene-
mapping. 2) Molecular genetics focuses on the structure, organization, and function of
genes at the molecular level. Molecular genetics is also concerned with the processes by
which genetic information is transferred and expressed. 3) Population genetics studies
genetic variation and changes in genes and allele frequencies within groups of individuals
of the same species over time.
6. What are some characteristics of model genetic organisms that make them useful for
genetic studies?
Solution:
Model genetic organisms have relatively short generation times, produce numerous
progeny, are amenable to laboratory manipulations, and can be maintained and propagated
inexpensively.
Section 1.2
7. When and where did agriculture first arise? What role did genetics play in the development
of the first domesticated plants and animals?
Solution:
Agriculture first arose 10,000 to 12,000 years ago in the area now referred to as the Middle
East (i.e., Turkey, Iran, Iraq, Syria, Jordan, and Israel). Early farmers selectively bred
individual wild plants or animals that had useful characteristics with others that had similar
useful traits. The farmers then selected for offspring that contained those useful features.
Early farmers did not completely understand genetics, but they clearly understood that
breeding individual plants or animals with desirable traits would lead to offspring that
contained these same traits. This selective breeding led to the development of domesticated
plants and animals.
8. Outline the notion of pangenesis and explain how it differs from the germ-plasm theory.
, Chapter One: Introduction to Genetics 3
Solution:
Pangenesis theorizes that information for creating each part of the offspring’s body
originates from each respective part of the parent’s body and is passed through the
reproductive organs to the embryo at conception. Pangenesis suggests that changes in parts
of the parent’s body may be passed to the offspring’s body. The germ-plasm theory, in
contrast, states that the reproductive cells (eggs and sperm) possess all of the information
required to make the complete body; the rest of the body contributes no information to the
next generation.
9. What does the concept of the inheritance of acquired characteristics propose and how is it
related to the notion of pangenesis?
Solution:
The theory of inheritance of acquired characteristics postulates that traits acquired during
one’s lifetime can be transmitted to offspring. It developed from pangenesis, which
postulates that information from all parts of one’s body is transmitted to the next
generation. Thus, according to the theory of inheritance of acquired characteristics, the
development of large bicep muscles through exercise would produce children with large
biceps.
10. What is preformationism? What did it have to say about how traits are inherited?
Solution:
Preformationism is the theory that the offspring results from a miniature adult that is
already preformed in the sperm or the egg. All traits would thus be inherited from only one
parent, either the father or the mother, depending on whether the homunculus (the
preformed miniature adult) resided in the sperm or the egg.
11. Define blending inheritance and contrast it with preformationism.
Solution:
The theory of blending inheritance proposes that the egg and sperm from two parents
contains material that blends upon conception, influencing the development of the
offspring. This theory indicates that the offspring is an equal blend of the two parents. In
preformationism, the offspring inherits all of its traits from one parent.
12. How did developments in botany in the seventeenth and eighteenth centuries contribute to
the rise of modern genetics?
Solution:
Botanists of the seventeenth and eighteenth centuries discovered that plants reproduce
sexually, enabling them to develop new techniques for crossing plants and creating plant
hybrids. These early experiments provided essential background work for Mendel’s plant
crosses. Mendel’s work laid the foundation for the study of modern genetics.
13. List some advances in genetics made in the twentieth century.
, 4 Chapter One: Introduction to Genetics
Solution:
1902 Proposal that genes are located on chromosomes by Walter Sutton
1910 Discovery of the first genetic mutation in a fruit fly by Thomas Hunt Morgan
1930 The foundation of population genetics by Ronald A. Fisher, John B. S. Haldane,
and Sewall Wright
1940s The use of viral and bacterial genetic systems
1953 Three-dimensional structure of DNA described by Watson and Crick
1966 Deciphering of the genetic code
1973 Recombinant DNA experiments
1977 Chemical and enzymatic methods for DNA sequencing developed by
Walter Gilbert and Frederick Sanger
1986 PCR developed by Kary Mullis
1990 Gene therapy
14. Briefly explain the contribution that each of the following persons made to the study of
genetics.
Solution:
a. Matthias Schleiden and Theodor Schwann
Proposed the concept of the cell theory, which indicated that the cell is the fundamental
unit of living organisms. Caused biologists interested in heredity to examine cell
reproduction.
b. August Weismann
Proposed the germ-plasm theory, which holds that cells in reproductive organs carry a
complete set of genetic information.
c. Gregor Mendel
First discovered the basic rules of inheritance.
d. James Watson and Francis Crick
Along with Rosalind Franklin and Maurice Wilkins, described the three-dimensional
structure of DNA.
e. Kary Mullis
Developed the polymerase chain reaction, used to quickly amplify small amounts of DNA.
Section 1.3
15. What are the two basic cell types (from a structural perspective) and how do they differ?
Solution:
The two basic cell types are prokaryotic and eukaryotic. Prokaryotic cells have neither
membrane-bound organelles nor a true nucleus. Their chromosomes are found within the
cytoplasm. Eukaryotic cells possess a membrane-bound nucleus and other membrane-
bound organelles such as an endomembrane system and mitochondria.
16. Outline the relations between genes, DNA, and chromosomes.
