Biology: An Interactive Tour
Biology: An Interactive Tour

Biology: An Interactive Tour

Lead Author(s): Robert Pozos

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Biology: An Interactive Tour is for a non-majors audience in technology-enhanced learning and makes the complex world of biological science approachable and relatable.

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Biology: An Interactive Tour introduces the content in a much more approachable way than traditional texts.

Includes homework sets with 30+ questions per chapter.

Embedded videos that apply biology concepts to the real world!

Comparison of Introduction to Biology Textbooks

Consider adding Biology: An Interactive Tour to your upcoming course. We’ve put together a textbook comparison to make it easy for you in your upcoming evaluation.

Top Hat

Bob, Pozos, “Biology: An Interactive Tour”, Only One Edition needed

Macmillan

Shuster, Michele & Janet Vigna & Matthew Tontonoz, Biology for a Changing World

Hard Copy

Taylor, Martha R., et al., Campbell Biology: Concepts & Connections

Pearson

Colleen Belk, & Virginia Borden Maier, Biology: Science for Life, 6th Edition

Pricing

Average price of textbook across most common format

Up to 40-60% more affordable

Lifetime access on any device

$63

E-book

$126

Hardcover print text only

$117

E-book

$166.95

Hardcover print text only

$95.95

E-book

$173.85

Hardcover print text only

Always up-to-date content, constantly revised by community of professors

Constantly revised and updated by a community of professors with the latest content

In-Book Interactivity

Includes embedded multi-media files and integrated software to enhance visual presentation of concepts directly in textbook

Only available with supplementary resources at additional cost

Customizable

Ability to revise, adjust and adapt content to meet needs of course and instructor

Built-In Interactive Assessment Questions

Assessment questions with feedback embedded throughout textbook

All-in-one Platform

Access to additional questions, test banks, and slides available within one platform

Pricing

Average price of textbook across most common format

Top Hat

Bob, Pozos, “Biology: An Interactive Tour”, Only One Edition needed

Up to 40-60% more affordable

Lifetime access on any device

Macmillan

Shuster, Michele & Janet Vigna & Matthew Tontonoz, Biology for a Changing World

$63

E-book

$126

Hardcover print text only

Hard Copy

Taylor, Martha R., et al., Campbell Biology: Concepts & Connections

$117

E-book

$166.95

Hardcover print text only

Pearson

Colleen Belk, & Virginia Borden Maier, Biology: Science for Life, 6th Edition

$95.95

E-book

$173.85

Hardcover print text only

Always up-to-date content, constantly revised by community of professors

Constantly revised and updated by a community of professors with the latest content

Top Hat

Bob, Pozos, “Biology: An Interactive Tour”, Only One Edition needed

Macmillan

Shuster, Michele & Janet Vigna & Matthew Tontonoz, Biology for a Changing World

Hard Copy

Taylor, Martha R., et al., Campbell Biology: Concepts & Connections

Pearson

Colleen Belk, & Virginia Borden Maier, Biology: Science for Life, 6th Edition

In-book Interactivity

Includes embedded multi-media files and integrated software to enhance visual presentation of concepts directly in textbook

Top Hat

Bob, Pozos, “Biology: An Interactive Tour”, Only One Edition needed

Macmillan

Shuster, Michele & Janet Vigna & Matthew Tontonoz, Biology for a Changing World

Only available with supplementary resources at additional cost

Hard Copy

Taylor, Martha R., et al., Campbell Biology: Concepts & Connections

Pearson

Colleen Belk, & Virginia Borden Maier, Biology: Science for Life, 6th Edition

Customizable

Ability to revise, adjust and adapt content to meet needs of course and instructor

Top Hat

Bob, Pozos, “Biology: An Interactive Tour”, Only One Edition needed

Pearson

Marieb & Hoehn – Human Anatomy and Physiology, 10th Edition

Wiley

Gerard Tortoria & Bryan Dickerson, Principles of Anatomy & Physiology, 14th Edition

McGraw-Hill

Kenneth Saladin, Anatomy and Physiology: The Unity of Form and Function, 7th Edition

All-in-one Platform

Access to additional questions, test banks, and slides available within one platform

Top Hat

Bob, Pozos, “Biology: An Interactive Tour”, Only One Edition needed

Pearson

Marieb & Hoehn – Human Anatomy and Physiology, 10th Edition

Wiley

Gerard Tortoria & Bryan Dickerson, Principles of Anatomy & Physiology, 14th Edition

McGraw-Hill

Kenneth Saladin, Anatomy and Physiology: The Unity of Form and Function, 7th Edition

About this textbook

Lead Author

Robert PozosUniversity of Minnesota-Duluth School of Medicine

Robert Pozos has extensive experience studying human response to environments resulting in hypothermia and hyperthermia. He established the hypothermia laboratory at University of Minnesota-Duluth School of Medicine and was a part of the chief civilian scientists at Naval Health Research Center in San Diego where he evaluated the thermal effectiveness of military garb for combat operations.

Contributing Authors

Christina AlevrasUniversity of Saint Joseph

Marion McClaryFairleigh Dickinson University

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Chapter 15: DNA

Figure 15.1: Parents pass their genetic code onto their children, which causes their resemblance as seen here in this image of a mother and her daughter. [1]

How much of you is a biological manifestation of your parent's DNA? Just like the mom and daughter in the image above, you are a direct result of your parents' DNA and the environment. In this chapter, we will focus on how DNA provides the “code” of all living organisms.

Concept Map

This chapter is divided into the four different sections as shown in the concept map below.

15.1 DNA Basics

Concept 15.1: The code for all our cells, organs and tissues is contained in nucleotides that compose DNA.​​

What is all the fuss about DNA, anyway? For many living systems, DNA holds the information required for the production of proteins that will be used in the execution of all functions of the cell. In addition, it determines the structure of the cell, organs, tissues and the organism (Concept 15.1). From a feedback point of view, DNA is the set point that determines the output of the cell’s metabolism. In addition, it receives input from various molecules that influence its commands. Thus, it is responsive to changes in its cellular environment. Finally, from a reproductive and evolutionary point of view, it is responsible for the transmission of all biological information ranging from enzymes and architecture of blood vessels to organ assembly and skin color. It is also the molecule that is transmitted during cell division so that every cell has the same information. However, in the grand scheme of biological evolution, DNA is a latecomer. 

Cells required some molecular structure that could coordinate and direct function. According to Figure 15.2, RNA was the first molecular controller for "living" systems. Its evolution took millions of years so that eventually DNA became the controller of protein synthesis. As you study the structure of DNA, keep in mind that it did not magically appear on the scene, but evolved from RNA. We will discuss the structure of DNA in this chapter and RNA in later chapters. 

Figure 15.2: Proposed Evolution of RNA to DNA​


​15.1.1 Central Dogma: DNA → RNA → Protein

Figure 15.3: DNA and RNA work together to produce an organism.​

How does one explain how living systems control their functions? The common answer is called the “Central Dogma,” which is based on the following: DNA directs RNA, which produces the protein. As always, it is not that simple. DNA itself is responsive to the environment and therefore can change, which would then change the final outcome: protein. Anywhere along the chain of command from DNA to RNA to protein, there can be changes which lead to mutation and form different structures. Evolution is primarily based on the changes in RNA and/or DNA over time that produced new forms of life. 

Question 15.01

As biological life started, _______\_\_\_\_\_\_\_ was the first molecule to direct cellular activity.


Question 15.02

Arrange in the proper order.

A

mRNA and tRNA

B

Protein

C

DNA

D

Organisms

E

Enzymes and cell structures and organs

DNA is a self-replicating, acidic molecule composed of a double strand of nucleotides that stores information concerning the production of protein. It is located in the chromosomes in the nucleus. Although it directs all protein development, 95% of it is not involved in protein synthesis. DNA in the nucleus in eukaryote cells forms a double helix, whereas the DNA in the mitochondria is circular. In prokaryotes, a more primitive life form, there is no nucleus, but DNA is in the cytoplasm. 

RNA is a single-stranded set of nucleotides whose molecule groups act as messengers, carrying the information from DNA to make protein. RNA forms include: 

  • Messenger RNA (mRNA), which is a photocopy of DNA. 
  • Transfer RNA (tRNA), which links DNA to amino acids involved in producing protein.
  • Ribosomal RNA (rRNA), which constitutes a majority of the ribosome and is the molecular platform on which mRNA and tRNA interact to form proteins. 

RNA was the first molecule used by bacteria and viruses to store information and direct protein synthesis. What was the reason for the evolution of DNA? RNA's structure is single-stranded and much more vulnerable to modification by external chemical forces. DNA, on the other hand, is more robust and able to transmit data faithfully from one generation to the next. Thus over millions of years, DNA became the molecule that assumed the control of cells. 

The functions of DNA and RNA depend on enzymes and ATP. Although these are not regularly shown nor discussed, protein synthesis would not occur without these two major chemical groups. 

Proteins are the functional form of the information. In many cases, they are the enzymes that control the chemical reactions in the cell. Proteins have other important functions, which are discussed in their own chapter.

We will study these molecules and their function in the next three chapters. Understanding the form and function of these molecules leads to knowing how life is organized and how it evolved. Biology is the study of energy capture and reproduction. These crucial functions are controlled by master molecules and the protein that they produce. 

15.1.2 What Are the Molecules that Make Up DNA?

DNA and RNA belong to a class of macromolecules known as nucleic acids. DNA stands for Deoxyribonucleic Acid, and RNA stands for Ribonucleic Acid. As with other macromolecules that you have learned about, DNA and RNA are made up of monomers, which in this case are called nucleotides. Three molecules make up a nucleotide: a five-carbon sugar, a phosphate group, and a nitrogenous base.

15.1.2.1 Five-Carbon Sugar (Pentose)

Both DNA and RNA have a five-carbon sugar (also known as pentose) as the center of their nucleotides. The five carbons of the sugar ring are labeled 1', 2', 3', 4' and 5' based on their position in the ring with respect to the central oxygen (O). Using this numbering system, we can indicate the location on the carbon ring where other molecules are attached. The major difference between a DNA nucleotide and an RNA nucleotide is the group attached to the 2' carbon of the sugar ring. In an RNA nucleotide, the sugar is ribose and has an OH group on its 2' carbon, while in DNA the sugar deoxyribose and the 2' carbon only has a hydrogen (H). Thus, the sugar is called “deoxy” because it is missing that oxygen (O).

Figure 15.4: Pentose sugars, such as 2-deoxyribose and ribose, are five-carbon sugars that are the key components of the chemical backbone of DNA and RNA. The carbon atoms are numbered from 1-5. In deoxyribose, the hydrogen ion on C2 that is bracketed does not have an oxygen. In ribose, the hydrogen ion on C2 which is bracketed has an oxygen attached to it. Deoxyribose connects a phosphate group at C4 and a nitrogenous base at C1.
Question 15.03

On the sugar ribose, the OH group is attached to which number carbon?


Question 15.04

DNA has ________\_\_\_\_\_\_\_\_ as a sugar that is part of its backbone.


Question 15.05

Each carbon as a letter associated with it. Identify the 3' carbon.


15.1.3 A Phosphate Group

Figure 15.5. The molecular backbone of DNA or RNA is the sugar​

Each nucleotide of DNA or RNA contains a phosphate group on the 5’ carbon. This group is important for the formation of DNA or RNA polymer chains from individual nucleotides. The phosphate group on the 5' carbon of one nucleotide can react with the OH group on the 3' carbon of the sugar ring of a different nucleotide to form a bond between two nucleotides; this makes single-stranded DNA or RNA. The sugar phosphate group forms the backbone of DNA or RNA to which the nitrogenous base will attach. 


15.1.4 A Nitrogenous Base

15.6.png
Figure 15.6: Only these four nitrogenous bases join with sugars and phosphate group to form one strand of DNA. These nitrogenous bases form the basis of the DNA alphabet, which directs the union of amino acids to form protein.

The last piece of a nucleotide we need to discuss is the nitrogenous base, which is attached to the 1’ carbon of the sugar. There are four different types of nitrogenous bases that can bind a deoxyribose sugar to make a nucleotide. These four bases fall into two groups:

1) Pyrimidines – nitrogenous bases with one carbon ring

Cytosine – C
Thymine – T

2) Purines – nitrogenous bases with two carbon rings

Adenine – A
Guanine – G


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15.1.5 Structures of DNA

​The primary structure of DNA is a single strand of sugar-phosphate groups along with their nucleotides. When the base pairs combine by way of hydrogen bonding, they produce a double-stranded DNA molecule which is the secondary structure of DNA. Although DNA is an acid, it has bases in the form of the purines and pyrimidines. So why is DNA and acid and not a base? The overall structure of DNA, especially the presence of phosphate groups, gives DNA its overall acidic nature. 

Figure 15.7: DNA Molecular structure. Hydrogen bonds between purines and pyrimidines link two strands of DNA.

​There is an interaction between the various nucleic bases which is represented in three-dimensional space giving the classic picture of DNA. Some scientists have used the analogy of DNA being similar to a twisted ladder. The rungs of the ladder are the nucleic acids which are electronically attracted to each other, giving a twisted appearance. 

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Figure 15.8: Primary, Secondary and Tertiary structures of DNA​.

DNA coils onto itself and produces major and minor grooves. These grooves are important since they will determine which part of the DNA can be easily accessed by different proteins. In addition as the DNA coils based on different electrical and chemical forces, it can twist to the right or the left. Presently the DNA most studied is B-DNA that twists to the right and has large grooves. There are other forms such as A-DNA and Z-DNA whose functions are not well understood. 

15.1.5.1 RNA

RNA is a single-stranded group of nucleic acids and preceded DNA by millions of years. Most primitive forms of life had RNA. Using the analogy of the ladder, RNA is only one half of the ladder, but it also has a three-dimensional structure based on the interactions of the nucleic acids with each other. RNA also differs from DNA since it has the nucleic acid, uracil, in place of thymine.

Figure 15.9.png
Figure 15.9: DNA and RNA structures. RNA can also for tertiary structures based on the hydrogen bonding between bases. ​​


There are a few rules of base pairing that we must discuss in order to understand the structure of DNA and how DNA can carry out its function.

15.1.5.2 Rule 1

Double-stranded DNA contains two anti-parallel single strands. This means the two strands are side by side in opposite directions. One runs from the 5' carbon to 3' carbon, while the second lays in the opposite 3’ to 5' direction.

15.1.5.3 Rule 2

Base pairing always occurs between a purine and a pyrimidine. Adenine always pairs with Thymine (A-T), and Guanine always pairs with Cytosine (G-C). The two strands intertwine like a twisted ladder, with the 5' to 3’ interactions of the nucleotides on the outside like the rails of a ladder and the base pairing between the nitrogenous bases occurring on the inside forming “rungs." The formation of the helix allows for long-chain molecules to be packed in a small space—the nucleus for example. 

Question 15.09

You have a tricorder that records and analyzes chemicals. Scanning your brother, the tricorder records levels of a compound that looks like DNA. Which of the following molecules would need to be excluded so that you are sure this is DNA?

A

Glucose

B

Pentose

C

Phosphate group

D

ATP


Question 15.10

The purines and pyrimidines are attached to each other by way of ________\_\_\_\_\_\_\_\_ bonding.


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15.2 Coding Nucleotide Sequences Make Genes

Concept 15.2: DNA is the key component of genes that transfer genetic information​ to the next generation.​​

The ability of DNA to store information comes from its nucleotide structure. As we have learned, there are four distinct nucleotides that can be used to make a molecule of DNA. The differences in nucleotides come from the four possible bases: adenine (A), thymine (T), guanine (G) and cytosine (C). The order of nucleotides in a strand of DNA is not random; the A, G, C and T nucleotides act as a molecular alphabet. A particular sequence of these nucleotides within a strand of DNA that codes for a protein is a “gene.” Thus, you may have also heard of DNA containing a “genetic code” or “genetic information.” These genes contain the information necessary to make a protein. Specific nucleotide sequences code for specific proteins. Genes usually code for a polypeptide (protein). Genes determine physical and chemical characteristics. Some characteristics are controlled by one gene (like the type of ear wax you produce) and are called monogenic. Most characteristics are controlled by multiple genes and are called polygenic. A common polygenic example is eye color, a physical characteristic determined by chemical reactions. Skin color is determined by 100 genes located on different chromosomes. Due to this fact, there can be a gradation of skin color.

Figure 15.10: All our chromosomes are composed of segments of DNA called genes that code for specific proteins.

In addition, genes may not code for certain characteristics. For example, if there is a lack of certain enzymes, or their control by other genes, to metabolize the sugar lactose, the person will not be able to metabolize lactose and will display signs such as bloating, diarrhea, etc. Both eye color and lactose intolerance are determined by genes and are called phenotypes.

Genes are also expressed at various times. Certain genetic diseases are manifested at different times in a person’s life. Diabetes Type 1, which is the phenotype of the lack of the production of insulin, does not occur at birth. It may occur over the lifespan of the individual. Thus, the genes produce the phenotype, but the manifestation of the phenotype varies.

To complicate this overall view, genes are not the only determinant of phenotype. The environment also plays a significant role. In many cases, the polygenetic susceptibility to diseases can be triggered by outside influences. For example, there is a strong genetic predisposition toward alcoholism in some individuals; however, it is not expressed unless the person drinks excessively. Put another way, certain genetic susceptibilities will not be activated unless certain environmental triggers are present.

The end result of these various factors is DNA in cells will be manifested in the tissues, the organs and the entire organism.

Figure 15.11: DNA in conjunction with environmental factors has the code for every organism. ​


Question 15.12

As a young medical examiner, your medical tricorder is recording a life form that may have a genetic code. Which of the following would have to be included so you could arrive at a conclusion that this was a life form with a genetic code?

A

Genes

B

DNA

C

Nucleotides

D

Tricorder would have to record all of the above


Question 15.13

Many attributes of living systems require many genes called ________\_\_\_\_\_\_\_\_ to program for proteins.


15.3 Genes Compose Chromosomes

Concept 15.3: Genes are the components of chromosomes that are the signature of a species.​



You may recall the structure of DNA as having the following components:

  • Nucleotide: A single monomer of DNA.
  • Single-stranded DNA: The linking of 5' and 3' carbons between nucleotides to create one strand of DNA (primary structure).
  • Double-stranded DNA (double helix): Two DNA strands running in opposite directions.
  • Double-stranded DNA: DNA connected by nuclear base pairing (secondary structure)
  • Three-dimensional DNA: DNA produced by chemical and electrical forces that cause the molecule to twist and for a double helix (tertiary structure).

How do these long strands of DNA fit into a tiny cell? The process involves "condensation” of the DNA into compact structures called chromosomes. Chromosomes consist of DNA and accessory proteins, which are organized in the following steps: 

Step 1: Long, double strands of DNA are wrapped around proteins called histones. The histones help facilitate the organization packing of the DNA into a smaller area. (One challenge with this organization is that part of the DNA must become unraveled during protein production.)

Step 2: The strands continue to be compressed until they are a certain dimension and are called chromatids. 

Step 3: The chromatids form the chromosomes. The chromosomes are an example of the cell shortening the 6-foot-long DNA into manageable chunks.

The packaging of DNA into a small compact molecular unit is essential for it to fit inside the nucleus. This solution causes a problem in that for the DNA to direct protein synthesis part of this molecular packaging has to be undone. This is accomplished by enzymes that unwrap a certain segment of the DNA. 

Figure 15.12: DNA Packaged into a Chromosome


Question 15.14

The purpose of DNA wrapping around histone is to ________\_\_\_\_\_\_\_\_ the length of the molecule.


Question 15.15

Which is the smallest?

A

Histones

B

Nucleosomes

C

Chromatosomes

D

Chromosomes

15.3.1 The Chromosome

In all our cells we have 23 pairs of the chromosomes, 22 of which are called autosomal and one pair that is called sex chromosomes since they determine biological sex. Of the pair, one chromosome is inherited from the paternal lineage and the other chromosome is inherited from the maternal lineage. Chromosomes are diffused in the nucleus during interphase (non-dividing) and are best seen in their compact form during cell division. Recent studies suggest that during interphase, each chromosome occupies a specific part of the nucleus

Figure 15.13: Chromosomal map of humans shows the 1-22 pairs which are autosomal and pair 23 (not labelled) which is the sex chromosomes (XY). The pairs represent the contribution from the father for one strand and the mother for the other. [2]​

Chromosomes vary in number and shape in different life forms. As an example, bacteria have two circular chromosomes, while humans and plants have linear chromosomes that are arranged in pairs. Reproductive cells (called gametes) are a major exception to this rule of all cells containing pairs of chromosomes. Gametes only contain one chromosome of each pair, so when gametes fuse during fertilization, the chromosomal count will be the same as the non-reproductive cells. During meiosis, the chromosomes separate so that each sperm or egg has only one set of chromosomes. If the sperm and egg have two chromosomal pairs when they join, the offspring will have 46 pairs of chromosomes—double the amount of DNA! This does not occur except in pathological conditions, and these offspring will not survive. 

Cells also contain two different types of chromosomes: those found in the nucleus and in the mitochondria. The nucleus contains linear chromosomes, while the mitochondria contain circular chromosomes. Circular chromosomes are also found in bacteria. This similarity between the circular DNA found in mitochondria and bacteria suggest that mitochondria at one time were bacteria that combined with another cell to form the current eukaryotes.

Figure 15.14: Circular Mitochondrial DNA. The DNA in mitochondria is circular and very distinctive from the DNA found in the nucleus, which is linear. The circular nature of mitochondrial DNA supports the idea that it was at one time separate from the cell.

The chromosomal map is also a way to study evolution. For example, human and chimpanzee chromosomes have very similar genetic maps. The biggest difference is that humans have one fewer pair of chromosomes compared to the great apes. The difference between the two groups is on chromosome 2A and 2B, which are separate on the chimpanzee but are combined in humans. This data suggests that Humans (Homo sapiens) are closely related to the chimpanzee. 


Figure 15.15. A chromosomal map demonstrating the difference between humans and chimpanzees. The major difference deals with chromosome 2 which in humans is a combination of chromosome 2A and 2B. ​

DNA plays a major role in determining the overall organism ranging from their biochemistry, structure and organs to how they interact. Changes in the DNA sequence will determine new life forms or species. This fundamental scientific fact is being used to correct various diseases that have a genetic basis as well as to generate new life forms.

Figure 15.16: Relationship between DNA (1, 2), genes (3), chromosomes (4), and genomes found in cells (5) which determine the overall organism (6).


Question 15.16

On an isolated part of Baja California, the indigenous people have stories about how the smoke from volcanoes can influence people’s behavior. You discover that the smoke influences the person’s histones. What function do histones have?

A

DNA coils around them

B

Nucleosomes coil around them

C

Nucleotides coil around them

D

Chromatids coil around them



Question 15.17

Chimpanzees and humans have a very similar chromosomal pattern. Which chromosome in humans suggests that there was a mutation in the ancestor of humans and chimpanzees?

A

The X chromosome, since it is only found in humans

B

Chromosome 2, since it identical to that in chimpanzees

C

The Y Chromosome, which is only found in chimpanzees

D

Chromosome 2, since it a merger of two separate chromosomes in chimpanzees


Question 15.18

In a chromosomal map, chromosome 1 is a pair with each one representing ________\_\_\_\_\_\_\_\_ contribution.


15.4 Chromosomes Make Up the Genome

Concept 15.4: Chromosomes determine the genome of all living systems.​

The genome of an organism is its complete set of genes organized into chromosomes. However, we have yet to discover the specifics of how each gene functions since many do not code for proteins. Therefore, many methods known as genomic mapping have been developed to identify the locus of a gene and the distances between genes. Genomic projects are designed to determine the complete nucleotide sequence of any organism, be it an animal, plant, fungus or virus. The National Institutes of Health has a database of 24,648 genomes ranging from bacteria and viruses to eukaryotes. The importance of this data cannot be overemphasized; it can be used in many different ways to find cures for diseases and to understand more about the evolutionary process. Click here for more information.

One of the goals of mapping the human genome is to understand and treat different genetic diseases. Genomes are determined by the use of sequencing machines and algorithms to arrive at an accurate representation of chromosomes.

The Human Genome Project (HGP) has revealed that there are approximately 20,500 human genes. The completed human sequence currently identifies the locations for each gene on the chromosomes. In addition to the nuclear genes, mitochondrial DNA contains 37 genes, all of which are essential for normal mitochondrial function. Thirteen of these genes provide instructions for synthesizing enzymes involved in oxidative phosphorylation. As you recall, oxidative phosphorylation is a process that uses oxygen and food to create adenosine triphosphate (ATP). 

The HGP also revealed the possibility of creating new life forms by combining nucleotides. This method resulted in a new species of self-replicating bacteria with 437 genes, 149 of which have a known function.

The point to be made from this research is twofold:

1. Modern scientific techniques will eventually elucidate all the functions of coding and non-coding genes in living systems.

2. Synthetic forms of “life” will be generated.

15.4.1 Money Still Matters

Funds continue to be the major determinant of how quickly research is accomplished. Initially, the Human Genome research was moving at a slow pace due to the process involved in universities garnering their funds through the federal government. The importance of having a registry of the human genome was not lost on private investors. With the advent of private funding, C. Venter was able to describe the Human Genome as quickly as the federally funded universities. As a result, his company has received patents on a large number of enzymes discovered in the study of the Human Genome. The implication of a private company owning patents on the Genome has raised ethical issues. There is concern that the private company can now work to develop new forms of life without governmental intrusion. This issue is still being hotly debated as to whether there should be control of scientific experiments that deal with manipulating the genome. 

15.4.2 The Global Genomic Initiative

The human genomic project was designed to focus on one organism at a time. However, biology is based on the interaction of various life forms in an ecosystem. Therefore, the Smithsonian Institute is sponsoring the Global Genomic Initiative.

Its goal is to catalog the genome of every plant, animal, fungus and algae. This ambitious project aims at sequencing the earth’s 1.3 million species. Its second goal is to store and preserve the genomic data for use by other scientists. Click here for more information.

Question 15.19

The human genome project has mapped all the ________\_\_\_\_\_\_\_\_ for the human species.

15.4.3 More than the Genome: Phenomics

It is readily recognized that there needs to be an overall approach towards analyzing the combined effects of genes and the environment on all phenotypes. The simple thinking of one gene affecting the expression on one phenotypic trait excluding any consideration of the environment has changed and has led to a new field of study called phenomics. By definition, phenomics is a study of an organism’s phenotypic traits by evaluating its genome and external environment. The external environment can include a host of factors, including chemical interactions inside the cell or outside the cell (i.e., hormones) as well as external stimuli (e.g., sunlight, pollution, temperature, etc.).

This new field embraces a study of all the steps involved in the production of protein, its expression and modification by external influences. At present, the emphasis is on using this approach for studying different diseases, but it can be used for any study dealing with phenotypes, such as intelligence or other traits. The importance of phenomics is the understanding that it is not only the genome that determines the phenotype. The complete set of proteins is produced by the genome as well as the metabolites.

Question 15.20

In attempting to make an artificial human, scientists are designing the clone to have the same number of genes as was reported from the human genome project. What number of genes would the lab have to put into each cell?

A

2,500

B

37

C

20,500

D

150

DNA determines the output of every cell. In this case, the DNA in skin cells is directing cells to produce enzymes (proteins) that will produce melanin. However, the enzymes are not functional. In this hypothetical case, receptors will sense that the enzymes are not functional, causing the comparator to continue transcription and translation. In this case, you have a positive feedback loop. The reason the cells are not functional is due to some problem with the coding at a number of sites: DNA, transcription or translation. The identification of the receptor and comparator have not been completely elucidated. 

15.5 Feedback Loop

Figure 15.17: DNA codes for proteins, but relies on various feedback mechanisms to produce the desired proteins. The feedback mechanisms involved in protein production, such as the receptor and comparator, have not been completely identified.​
Question 15.21

Melanin is produced by cells. Reviewing the feedback loop, what happens when the set point (nucleotides) for DNA is absent?

A

Melanin will still be produced

B

Melanin will not be produced

C

There is no effect on melanin production

D

Mitochondria will independently make melanin


Question 15.22

Given that DNA is different from RNA, which of the following is true?

A

RNA is double-stranded, and DNA is not

B

DNA has thymine, and RNA has uracil

C

RNA is circular, and DNA is straight

D

All answers are correct

E

B and C are correct


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Question 15.24

Arrange in the correct order starting from the simplest to the most complex.

A

DNA is complexed with histones to form nucleosomes

B

250 nm wide fiber produces the chromatid

C

Nucleosomes consists of 8 histone proteins around which DNA wraps

D

Nucleosomes fold up to produce 30 nm fiber


Question 15.25

You are trying to commercially synthesize a human in the lab. How many genes would it have to have?


Figure 15.18: Chapter overview of DNA.​


15.6 Vocabulary Questions

Vocabulary Question 15.01

Interaction between nitrogenous bases on nucleotides to form double-stranded DNA.


Vocabulary Question 15.02

Long strands of double-stranded DNA packaged around proteins.


Vocabulary Question 15.03

Five-carbon sugar of DNA nucleotides that lacks an oxygen on the 2’ carbon.


Vocabulary Question 15.04

Short for Deoxyribonucleic acid, a polymer of nucleotides that stores cellular information.


Vocabulary Question 15.05

The protein responsible for synthesizing new DNA strands through base pairing.


Vocabulary Question 15.06

The process by which new copies of DNA are made. The basic steps include unwinding of double-stranded DNA by helicase to make a template strand and synthesis of a new strand through the addition of nucleotides by DNA polymerase.


Vocabulary Question 15.07

Another name for double-stranded DNA.


Vocabulary Question 15.08

A full set of chromosomes.


Vocabulary Question 15.09

The protein that unwinds double-stranded DNA during DNA replication.


Vocabulary Question 15.10

Group attached to the 1’ carbon of DNA and RNA. There are four bases in DNA, adenine (A), cytosine (C), guanine (G), and thymine (T).


Vocabulary Question 15.11

Monomer of DNA and RNA that consists of a five-carbon sugar, a phosphate group, and a nitrogenous base.


Vocabulary Question 15.12

Attached on the 5’ carbon of the central sugar of DNA and RNA, it can interact with the 3’ carbon of other nucleotides for form a single strand of DNA.


Vocabulary Question 15.13

The functional form of cellular information encoded by DNA.


Vocabulary Question 15.14

Nitrogenous base with two carbon rings (guanine and adenine).


Vocabulary Question 15.15

Nitrogenous bases with one carbon ring (cytosine and thymine).


Vocabulary Question 15.16

Five-carbon sugar of RNA with an OH group on the 2’ carbon (compared to deoxyribose of DNA that lacks an oxygen on the 2’ carbon).


Vocabulary Question 15.17

Short for Ribonucleic acid, it is a polymer of nucleotides that acts as a messenger between DNA and proteins.


Vocabulary Question 15.18

The term to describe the nature of DNA replication. Two new DNA molecules are made from one original molecule. Each new DNA molecule has one strand from the original molecule and a new strand.

15.7 Image Credits

[1] Image courtesy of taoheed_kasumu in the Public Domain.

[2] Image courtesy of National Human Genome Research Institute in the Public Domain.