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Biology assignment on Gregor Mendel’s Experiments, Theories, and Finding, Punnett Squares, Cancer Risk Factors
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Unit II Assignment—Genetics Worksheet
Gregor Mendel’s Experiments, Theories, and Findings
1. Mendel observed that pea plants had traits, such as color, that were either “one or the other,” never
something in between. Discuss the correlation between Mendel’s factors, what they might be, and why
pea plant traits come in one form or another—e.g., gray or dark red—rather than blended.
Your response must be at least 75 words in length. (Type your response in the blank area below; it will
expand as needed.)
2. Let’s imagine that we are studying only one trait, that of green- or yellow-colored seeds. Mendel bred
his peas until they either produced seeds of one color or the other. These purebred plants he called the p
generation (“p” for parental generation). He then cross bred green plants with yellow ones and discovered
that all the offspring were yellow-colored. Mendel called the offspring of the purebred plants the F1
generation.
Explain why all the offspring in the F1 generation were yellow instead of half being yellow and half green,
or some other mix of the colors. Hint: Remember that Mendel coined the terms dominant and recessive.
Your response must be at least 75 words in length. (Type your response in the blank area below; it will
expand as needed.)
Punnett Squares
Reginald Punnett was a British geneticist who developed the Punnett square to explain how the
chromosomes of parents cross and produce offspring. In order to solve genetics problems using a
Punnett square, it is necessary to a) understand the associated vocabulary and b) understand some of
the rules for solving the problems.

Before you continue with the problems below, review the meaning of the terms allele, dominant,
recessive, homozygous, heterozygous, genotype and phenotype.

You should also review the Punnett Square Basics video linked in the unit lesson.
In this first problem (question #3), the key and genotype of the parents will be done for you as an
example. For problems #4 and #5, you will fill in those details based on the information in the question.
Remember, when asked for the genotypic ratio, it may be expressed as 25%(GG):50%(Gg):25%(gg), for
example. Or, you may write it more succinctly as 1GG:2Gg:1gg. Either way will be correct.
The phenotypic ratio will use descriptive terms, for example, 3(Green):1(clear), 2(Green):2(clear), or
whatever it may be depending on the results of your cross.
3. In corn plants, the allele for green kernels (G) is dominant over clear kernels (g). Cross a homozygous
dominant plant with a homozygous recessive plant.
Fill in the Punnett square below and give the ratios for each question beneath the Punnett Square.
Key: G = green kernels, g = clear kernels
Genotype of parents: _GG_ x _gg_
Parent #1
Parent #2
What is the genotypic ratio of the offspring in Question 3?
What is the phenotypic ratio of the offspring in Question 3?
4. Yellow seeds are dominant over green seeds in pea plants. Cross a heterozygous (yellow seeded)
plant with a green seeded plant.
Key: __________
Genotype of parents:
__________ x __________
Parent #1
Parent #2
What is the genotypic ratio of the offspring in Question 4?
What is the phenotypic ratio of the offspring in Question 4?
5. Now cross two of the heterozygous F1 offspring from question #2.
Parent #1
Parent #2
What is the genotypic ratio of the offspring in Question 5?
What is the phenotypic ratio of the offspring in Question 5?
6. Consider the resulting ratio of crossing the two heterozygous pea plants in question #5. We will use
this ratio in a short activity exploring probability. Keep in mind that crossing two individuals that are
heterozygous for a certain trait is similar to flipping two coins. Each coin has two sides (we might think of
each side as an “allele”) and the chances of flipping heads/heads, heads/tails or tails/tails should be
similar to the ratio we see when crossing two heterozygotes.
For this simple activity, you will need two coins (pennies, nickels, dimes, quarters, or a mix of any of
those). Alternatively, you may google a coin-flipper simulator that will allow you to flip two coins at once.
You will also need a piece of scratch paper and a pen or pencil.
Directions: Flip the two coins simultaneously at least 50 times. For each flip of the pair of coins, you will
record the results on a piece of scratch paper. You might set up a table like the one below to record your
results. Once you have flipped the coins at least 50 times, enter the number of heads/heads, heads/tails
and tails/tails in Table 1 below.
Now determine the ratio for your results. You will do this by dividing the number for each result by the
total number of flips, and then multiply by 100.
(Example: If the number of heads/heads is 9 then 9/50 = .18, .18×100 = 18%), Repeat this mathematical
procedure for heads/tails and tails/tails)
Table 1
Heads/heads (hh)
Head/tails (ht)
Tails/tails (tt)
Ratio (hh:ht:tt)
Compare the resulting ratio from the question #5 cross of two heterozygous parents to the ratio from the
coin flipping exercise. Are there similarities? If so, what are they?
What might be done to make the ratio from the coin flipping exercise become more similar to the ratio
from question #5? (Hint: Consider that more data equals better accuracy.)
Cancer Risk Factors
7. This question deals with cancer and risk factors. Begin by going to the website http://www.cancer.org/
Click “Cancer A-Z” in the upper left corner. The page that comes up will provide links to information on
breast cancer, colon and rectal cancer, lung cancer, prostate cancer, and skin cancer. Review the
information for each these cancers.
Next, write an essay that briefly discusses your own risk factors for each type of cancer and steps you
might take to decrease those risk factors. Be sure to address all five types of cancer.
You do not have to disclose any actual personal information if you do not wish to do so. You may create a
fictional character and discuss his or her risk factors instead. Be sure to address all five types of cancer.
Your response must be at least 300 words in length. (Type your response below)
UNIT II STUDY GUIDE
Cancer and Genes
Course Learning Outcomes for Unit II
Upon completion of this unit, students should be able to:
1. Define the basic concepts of biological sciences.
1.1 Recognize risk factors for cancer.
1.2 Identify what happens during the phases of mitosis and meiosis.
4. Explain Mendel’s approach to studying genetics.
4.1 Discuss dominant alleles and recessive alleles.
4.2 Recall that chromosomes come in pairs and carry traits that are inherited by offspring.
4.3 Discuss Mendel’s law of independent assortment.
8. Interpret biological data.
8.1 Record flower color genotypes.
8.2 Delineate a Punnett square.
Course/Unit
Learning Outcomes
1.1
1.2
4.1
4.2
4.3
8.1
8.2
Learning Activity
Unit Lesson
Chapter 6
Unit II Assignment
Unit Lesson
Chapter 6
Chapter 7
Video: Meiosis, Zygotes, and Mutations
Unit II Assessment
Chapter 8
Video: DNA and Inheritance: Heredity
Unit II Assignment
Unit Lesson
Chapter 8
Video: DNA and Inheritance: Heredity
Video: Mendel, DNA, Genes, and Chromosomes
Video: Meiosis, Zygotes, and Mutations
Unit II Assignment
Unit Lesson
Chapter 8
Video: DNA and Inheritance: Heredity
Unit II Assignment
Unit Lesson
Chapter 8
Video: DNA and Inheritance: Heredity
Unit II Assignment
Unit Lesson
Chapter 8
Video: DNA and Inheritance: Heredity
Video: Mendel, DNA, Genes, and Chromosomes
Unit II Assignment
BIO 1100, Non-Majors Biology
1
Reading Assignment
UNIT x STUDY GUIDE
Title
Chapter 6: Cancer
Chapter 7: Fertility, pp. 124–130
Chapter 8: Does Testing Save Lives?
Cambridge Educational. (2005). Mendel, DNA, genes, and chromosomes (Segment 3 of 5) [Video file].
Retrieved from
https://libraryresources.columbiasouthern.edu/login?auth=CAS&url=https://fod.infobase.com/PortalPl
aylists.aspx?wID=273866&xtid=33836&loid=20017
For a transcript of this video segment, click here.
Cambridge Educational. (2005). Meiosis, zygotes, and mutations (Segment 4 of 5) [Video file]. Retrieved from
https://libraryresources.columbiasouthern.edu/login?auth=CAS&url=https://fod.infobase.com/PortalPl
aylists.aspx?wID=273866&xtid=33836&loid=20018
For a transcript of this video segment, click here.
Video Education America. (2016). DNA and inheritance: Heredity [Video file]. Retrieved from
http://fod.infobase.com.libraryresources.columbiasouthern.edu/p_ViewVideo.aspx?xtid=129089&tScript=0
For a transcript of this video, click here.
Unit Lesson
How do humans and other organisms grow, repair themselves, and maintain their health? Why does our skin
grow back when damaged while nervous tissue, cardiac tissue, and other tissues do not? How can a starfish
regenerate a lost appendage? How do bacteria multiply so quickly? Why do we look different from our siblings
when we have the same parents? Why do some people develop cancer and others do not?
These are all questions that can be answered using information about cell reproduction, genetics, and cancer.
In this unit, you will learn how cells divide, how information is passed, and how you can reduce your chances
of developing cancer. This is an exciting unit because you will develop an understanding of why you have the
characteristics that you possess.
Almost 600,000 people die each year in the United States from cancer (National Cancer Institute, n.d.-b). It is
the second-highest cause of death in the United States—the first is heart disease. Statistically speaking, a
person has about a one-in-four chance of developing some form of cancer within his or her lifetime (National
Cancer Institute, n.d.-b). That one-in-four chance may increase or decrease depending upon numerous
factors, most of which are derived from lifestyle choices. It is important that you understand more about
cancer because the likelihood that you or someone you love will develop cancer is somewhat high. In
previous years, cancer was a death sentence; however, through years of research, scientists now understand
the disease better and can treat or cure some forms of cancer.
BIO 1100, Non-Majors Biology
2
UNIT x STUDY GUIDE
Title
Although they can be beautiful, cancer cells are potentially deadly.
(Fox, 1987a, 1987b, 1987c)
In Chapter 6, “Cancer,” you will learn what cancer is, how cancer affects the human body, why cancer occurs,
and what treatment options exist for fighting cancer. You will also learn about different types of cancer and
genes or risk factors that increase your possibility of developing cancer. Understanding the risk factors
associated with cancer will help decrease your chances of developing cancer in the future.
Simply stated, cancer is uncontrolled cell division. In order to understand cancer, you must first understand
controlled cell division. Most cells in the human body reproduce. This is known as cellular division and occurs
through one of two processes in the human body: mitosis or meiosis.
Somatic cells (body cells other than cells made for reproduction) that undergo cell division do so by mitosis.
When mitosis occurs, a single cell makes an exact copy and divides. The result of mitosis is two genetically
identical daughter cells (Belk & Maier, 2019). Our cells that undergo mitosis do so in order that we can grow,
repair, and maintain our tissues.
Cell going through mitosis stages; from left: prophase, anaphase, and telophase
(van Heesbeen, 2008a, 2008b, 2008c)
Not all body cells divide or reproduce. This means when some types of cells are damaged or lost, they are
damaged or lost forever. Cells in the human body that do not reproduce include skeletal muscle cells,
neurons, and cardiac muscle cells.
Would we want all cells to produce identical copies? The answer is no, not for reproduction. If every cell was
identical, every person would be identical. Every plant would be identical. Virtually every organism would be
identical. Diversity is an important key to life on this planet. It enables organisms to mutate and adapt, such as
developing and passing on important traits. One example would be a population in which some organisms
possess a genetic trait toward greater resistance to disease that could save the organism’s entire species
from becoming extinct in the event of a serious disease outbreak. An organism population with diverse
genetic variability has more chance of survival than one with more limited genetic variability.
BIO 1100, Non-Majors Biology
3
Gametes (sperm and egg cells) do not undergo mitosis. Gametes undergo a process
called meiosis
UNIT x STUDY
GUIDE(Belk &
Maier, 2019), which is discussed in Chapter 7. Meiosis is referred to as reductional
Title division, in which one cell
divides into four cells that each contain half the number of chromosomes compared to the number contained
in the original cell before it divided. During meiosis, genetic information crosses over and aligns randomly on
the resulting chromosome and, therefore, produces cells that are not genetically identical. This allows for
diversity among sperm and eggs.
Cell division does not always happen as it should—sometimes mistakes occur. Think of it this way: If you
were to copy information from a note, you might make a mistake and copy down the wrong information. For
example, you may copy the word not instead of note. Mistakes similar to this sometimes occur when cells
undergo mitosis or meiosis. When such a mistake occurs during cell division, it is referred to as a mutation
(Belk & Maier, 2019). Mutation is random and is one of the forces that drive evolution. Mutations can be
detrimental because, when a mistake occurs,, something may go wrong. However, some mutations do not
matter, some can be good, but, as mentioned, some mutations can result in detrimental situations, such as
the development of cancer.
Not all cancer results from mutated information in DNA. Some forms of cancer—as well as many other
characteristics—are passed to us from our parents. In Chapter 8, “Does Testing Save Lives?” you will learn
about the basic concepts of the inheritance of traits and how genes interact with the environment. You will
also learn to compute possible offspring outcomes using Punnett squares.
Our knowledge about genes and genetic information began when a brilliant Austrian monk, Gregor Mendel,
conducted experiments on pea plants. Mendel conducted his work around 1855-1865. He published his
findings in 1865, but his work was not appreciated—perhaps not understood?—until after the turn of the
century. Mendel died in 1884, and unfortunately, the abbot who succeeded him burned all of Mendel’s
papers; this was a great loss to science. However, Mendel’s work was rediscovered by scientists in the early
1900s (Belk & Maier, 2019).
Mendel figured out that the “factors” he was studying came in pairs. Since then, Francis Watson and James
Crick have been credited with the discovery of the structure of DNA with the help of Rosalind Franklin, who
used X-ray crystallography to capture images of DNA (Science History Institute, n.d.). Our knowledge of
genetics continues to increase. For example, we now know that chromosomes do indeed come in pairs,
something Mendel only suspected.
One aspect that determines the success of a scientific study is using the right subject. Mendel did just that.
He studied pea plants, which reproduce sexually. Mendel was able to control the plants’ reproduction by
removing the flowers’ reproductive
organs and fertilizing the plants
manually. What patience he must
have had! It is estimated that over
the course of his studies, Mendel
raised about 30,000 plants
(Biography, 2014).
Mendel observed that pea plants
had some traits that were “eitheror,” with only two alternatives. His
plant’s flowers were either purple
or white, the seeds were either
round or wrinkled, the seeds’ color Mendel’s seven traits
was either yellow or green, and so (Ruiz, 2006)
on. Mendel believed that heredity was carried from parents to offspring by “factors.” He observed that
traits, such as color, were either one or the other, never something in between. What does this tell you
about the “factors”?”
Mendel bred his peas until they either produced all of one trait or the other, such as all yellow seeds or all
green seeds. Once he was sure that the plants were either one trait or the other, yellow or green, he crossed
them, breeding, for example, yellow-seeded plants with green-seeded plants. He called the purebred plants
the P generation (for parental). He discovered that all the offspring looked the same. For example, crossing
BIO 1100, Non-Majors Biology
4
yellow -seeded plants with green-seeded plants all resulted in yellow-colored seed
OneGUIDE
would think
UNIT plants.
x STUDY
that the offspring of the yellow-seeded and green-seeded plants would be halfTitle
yellow and half green, or a
mixture of the colors, but they were not. Mendel called this generation of plants the F1 generation, “F”
standing for filial, Latin for daughter.
Therefore, if you cross an organism that is purebred for a specific trait with another purebred organism with a
different allele for that trait, the first generation is called the F1 generation. All of the offspring in the F1
generation will have the phenotype of the dominant allele, and they will all be heterozygous in their genotype.
In your assignment for this unit, you are asked about crossing F1 organisms with other F1 organisms. This
time you will get different results, and the second generation is called the F2 generation. You will determine
the phenotypes and the genotypes of the F2 generation.
Why did Mendel not use people or elephants or giant sequoia trees? Is it ethical to pick traits from two people
and have them mate to determine the offspring? How much space would it take to study elephants or giant
sequoia trees? How much food would it take to feed people and elephants? As mentioned, Mendel chose his
subject wisely—not only could he easily manipulate fertilization of his plants, but he could also eat them, and
they did not require a tremendous amount of space or resources.
The most important characteristic of Mendel’s peas was mentioned earlier—that Mendel was able to
manipulate the fertilization of the pea plants (Belk & Maier, 2019). Significant characteristics of the pea plant
include these characteristics:








it can be self-fertilized or cross-fertilized,
it is easy to grow and cultivate,
each pea is a different fertilization event,
it has seven characteristics that have only two phenotypes (dominant/recessive),
it can be true bred (has a certain phenotype and only produces offspring with the same phenotype),
it is an annual (life cycle of growing from a seed to producing seeds is one year and then dies),
it is diploid (contains two sets of chromosomes—one from each parent), and
it relies on sexual reproduction.
Mendel was also fortunate that each of the seven traits he studied are on separate chromosomes. For
example, if flower color and seed shape had been on the same chromosome, he might not have figured out
independent assortment, because color and wrinkling would have gone together instead of being independent
(Belk & Maier, 2019).
The genetic composition of an individual is known as the person’s genotype. The genes then result in various
physical traits known as phenotypes. Variations of genes are called alleles. An organism that is produced by
sexual reproduction receives one gene from each parent. When an organism receives the same allele from
each parent, it is said to be homozygous for that trait. When the organism receives a different allele from each
parent, it is heterozygous (Belk & Maier, 2019). So, which trait “wins out” and shows through?
Human and many other organisms’ genetics are not simple. Many characteristics and traits are determined by
multiple genes a …
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Biology assignment on Gregor Mendel’s Experiments, Theories, and Finding, Punnett Squares, Cancer Risk Factors
unitii_assignment_worksheet_update.docx

unitiistudy_guide.pdf

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Unit II Assignment—Genetics Worksheet
Gregor Mendel’s Experiments, Theories, and Findings
1. Mendel observed that pea plants had traits, such as color, that were either “one or the other,” never
something in between. Discuss the correlation between Mendel’s factors, what they might be, and why
pea plant traits come in one form or another—e.g., gray or dark red—rather than blended.
Your response must be at least 75 words in length. (Type your response in the blank area below; it will
expand as needed.)
2. Let’s imagine that we are studying only one trait, that of green- or yellow-colored seeds. Mendel bred
his peas until they either produced seeds of one color or the other. These purebred plants he called the p
generation (“p” for parental generation). He then cross bred green plants with yellow ones and discovered
that all the offspring were yellow-colored. Mendel called the offspring of the purebred plants the F1
generation.
Explain why all the offspring in the F1 generation were yellow instead of half being yellow and half green,
or some other mix of the colors. Hint: Remember that Mendel coined the terms dominant and recessive.
Your response must be at least 75 words in length. (Type your response in the blank area below; it will
expand as needed.)
Punnett Squares
Reginald Punnett was a British geneticist who developed the Punnett square to explain how the
chromosomes of parents cross and produce offspring. In order to solve genetics problems using a
Punnett square, it is necessary to a) understand the associated vocabulary and b) understand some of
the rules for solving the problems.

Before you continue with the problems below, review the meaning of the terms allele, dominant,
recessive, homozygous, heterozygous, genotype and phenotype.

You should also review the Punnett Square Basics video linked in the unit lesson.
In this first problem (question #3), the key and genotype of the parents will be done for you as an
example. For problems #4 and #5, you will fill in those details based on the information in the question.
Remember, when asked for the genotypic ratio, it may be expressed as 25%(GG):50%(Gg):25%(gg), for
example. Or, you may write it more succinctly as 1GG:2Gg:1gg. Either way will be correct.
The phenotypic ratio will use descriptive terms, for example, 3(Green):1(clear), 2(Green):2(clear), or
whatever it may be depending on the results of your cross.
3. In corn plants, the allele for green kernels (G) is dominant over clear kernels (g). Cross a homozygous
dominant plant with a homozygous recessive plant.
Fill in the Punnett square below and give the ratios for each question beneath the Punnett Square.
Key: G = green kernels, g = clear kernels
Genotype of parents: _GG_ x _gg_
Parent #1
Parent #2
What is the genotypic ratio of the offspring in Question 3?
What is the phenotypic ratio of the offspring in Question 3?
4. Yellow seeds are dominant over green seeds in pea plants. Cross a heterozygous (yellow seeded)
plant with a green seeded plant.
Key: __________
Genotype of parents:
__________ x __________
Parent #1
Parent #2
What is the genotypic ratio of the offspring in Question 4?
What is the phenotypic ratio of the offspring in Question 4?
5. Now cross two of the heterozygous F1 offspring from question #2.
Parent #1
Parent #2
What is the genotypic ratio of the offspring in Question 5?
What is the phenotypic ratio of the offspring in Question 5?
6. Consider the resulting ratio of crossing the two heterozygous pea plants in question #5. We will use
this ratio in a short activity exploring probability. Keep in mind that crossing two individuals that are
heterozygous for a certain trait is similar to flipping two coins. Each coin has two sides (we might think of
each side as an “allele”) and the chances of flipping heads/heads, heads/tails or tails/tails should be
similar to the ratio we see when crossing two heterozygotes.
For this simple activity, you will need two coins (pennies, nickels, dimes, quarters, or a mix of any of
those). Alternatively, you may google a coin-flipper simulator that will allow you to flip two coins at once.
You will also need a piece of scratch paper and a pen or pencil.
Directions: Flip the two coins simultaneously at least 50 times. For each flip of the pair of coins, you will
record the results on a piece of scratch paper. You might set up a table like the one below to record your
results. Once you have flipped the coins at least 50 times, enter the number of heads/heads, heads/tails
and tails/tails in Table 1 below.
Now determine the ratio for your results. You will do this by dividing the number for each result by the
total number of flips, and then multiply by 100.
(Example: If the number of heads/heads is 9 then 9/50 = .18, .18×100 = 18%), Repeat this mathematical
procedure for heads/tails and tails/tails)
Table 1
Heads/heads (hh)
Head/tails (ht)
Tails/tails (tt)
Ratio (hh:ht:tt)
Compare the resulting ratio from the question #5 cross of two heterozygous parents to the ratio from the
coin flipping exercise. Are there similarities? If so, what are they?
What might be done to make the ratio from the coin flipping exercise become more similar to the ratio
from question #5? (Hint: Consider that more data equals better accuracy.)
Cancer Risk Factors
7. This question deals with cancer and risk factors. Begin by going to the website http://www.cancer.org/
Click “Cancer A-Z” in the upper left corner. The page that comes up will provide links to information on
breast cancer, colon and rectal cancer, lung cancer, prostate cancer, and skin cancer. Review the
information for each these cancers.
Next, write an essay that briefly discusses your own risk factors for each type of cancer and steps you
might take to decrease those risk factors. Be sure to address all five types of cancer.
You do not have to disclose any actual personal information if you do not wish to do so. You may create a
fictional character and discuss his or her risk factors instead. Be sure to address all five types of cancer.
Your response must be at least 300 words in length. (Type your response below)
UNIT II STUDY GUIDE
Cancer and Genes
Course Learning Outcomes for Unit II
Upon completion of this unit, students should be able to:
1. Define the basic concepts of biological sciences.
1.1 Recognize risk factors for cancer.
1.2 Identify what happens during the phases of mitosis and meiosis.
4. Explain Mendel’s approach to studying genetics.
4.1 Discuss dominant alleles and recessive alleles.
4.2 Recall that chromosomes come in pairs and carry traits that are inherited by offspring.
4.3 Discuss Mendel’s law of independent assortment.
8. Interpret biological data.
8.1 Record flower color genotypes.
8.2 Delineate a Punnett square.
Course/Unit
Learning Outcomes
1.1
1.2
4.1
4.2
4.3
8.1
8.2
Learning Activity
Unit Lesson
Chapter 6
Unit II Assignment
Unit Lesson
Chapter 6
Chapter 7
Video: Meiosis, Zygotes, and Mutations
Unit II Assessment
Chapter 8
Video: DNA and Inheritance: Heredity
Unit II Assignment
Unit Lesson
Chapter 8
Video: DNA and Inheritance: Heredity
Video: Mendel, DNA, Genes, and Chromosomes
Video: Meiosis, Zygotes, and Mutations
Unit II Assignment
Unit Lesson
Chapter 8
Video: DNA and Inheritance: Heredity
Unit II Assignment
Unit Lesson
Chapter 8
Video: DNA and Inheritance: Heredity
Unit II Assignment
Unit Lesson
Chapter 8
Video: DNA and Inheritance: Heredity
Video: Mendel, DNA, Genes, and Chromosomes
Unit II Assignment
BIO 1100, Non-Majors Biology
1
Reading Assignment
UNIT x STUDY GUIDE
Title
Chapter 6: Cancer
Chapter 7: Fertility, pp. 124–130
Chapter 8: Does Testing Save Lives?
Cambridge Educational. (2005). Mendel, DNA, genes, and chromosomes (Segment 3 of 5) [Video file].
Retrieved from
https://libraryresources.columbiasouthern.edu/login?auth=CAS&url=https://fod.infobase.com/PortalPl
aylists.aspx?wID=273866&xtid=33836&loid=20017
For a transcript of this video segment, click here.
Cambridge Educational. (2005). Meiosis, zygotes, and mutations (Segment 4 of 5) [Video file]. Retrieved from
https://libraryresources.columbiasouthern.edu/login?auth=CAS&url=https://fod.infobase.com/PortalPl
aylists.aspx?wID=273866&xtid=33836&loid=20018
For a transcript of this video segment, click here.
Video Education America. (2016). DNA and inheritance: Heredity [Video file]. Retrieved from
http://fod.infobase.com.libraryresources.columbiasouthern.edu/p_ViewVideo.aspx?xtid=129089&tScript=0
For a transcript of this video, click here.
Unit Lesson
How do humans and other organisms grow, repair themselves, and maintain their health? Why does our skin
grow back when damaged while nervous tissue, cardiac tissue, and other tissues do not? How can a starfish
regenerate a lost appendage? How do bacteria multiply so quickly? Why do we look different from our siblings
when we have the same parents? Why do some people develop cancer and others do not?
These are all questions that can be answered using information about cell reproduction, genetics, and cancer.
In this unit, you will learn how cells divide, how information is passed, and how you can reduce your chances
of developing cancer. This is an exciting unit because you will develop an understanding of why you have the
characteristics that you possess.
Almost 600,000 people die each year in the United States from cancer (National Cancer Institute, n.d.-b). It is
the second-highest cause of death in the United States—the first is heart disease. Statistically speaking, a
person has about a one-in-four chance of developing some form of cancer within his or her lifetime (National
Cancer Institute, n.d.-b). That one-in-four chance may increase or decrease depending upon numerous
factors, most of which are derived from lifestyle choices. It is important that you understand more about
cancer because the likelihood that you or someone you love will develop cancer is somewhat high. In
previous years, cancer was a death sentence; however, through years of research, scientists now understand
the disease better and can treat or cure some forms of cancer.
BIO 1100, Non-Majors Biology
2
UNIT x STUDY GUIDE
Title
Although they can be beautiful, cancer cells are potentially deadly.
(Fox, 1987a, 1987b, 1987c)
In Chapter 6, “Cancer,” you will learn what cancer is, how cancer affects the human body, why cancer occurs,
and what treatment options exist for fighting cancer. You will also learn about different types of cancer and
genes or risk factors that increase your possibility of developing cancer. Understanding the risk factors
associated with cancer will help decrease your chances of developing cancer in the future.
Simply stated, cancer is uncontrolled cell division. In order to understand cancer, you must first understand
controlled cell division. Most cells in the human body reproduce. This is known as cellular division and occurs
through one of two processes in the human body: mitosis or meiosis.
Somatic cells (body cells other than cells made for reproduction) that undergo cell division do so by mitosis.
When mitosis occurs, a single cell makes an exact copy and divides. The result of mitosis is two genetically
identical daughter cells (Belk & Maier, 2019). Our cells that undergo mitosis do so in order that we can grow,
repair, and maintain our tissues.
Cell going through mitosis stages; from left: prophase, anaphase, and telophase
(van Heesbeen, 2008a, 2008b, 2008c)
Not all body cells divide or reproduce. This means when some types of cells are damaged or lost, they are
damaged or lost forever. Cells in the human body that do not reproduce include skeletal muscle cells,
neurons, and cardiac muscle cells.
Would we want all cells to produce identical copies? The answer is no, not for reproduction. If every cell was
identical, every person would be identical. Every plant would be identical. Virtually every organism would be
identical. Diversity is an important key to life on this planet. It enables organisms to mutate and adapt, such as
developing and passing on important traits. One example would be a population in which some organisms
possess a genetic trait toward greater resistance to disease that could save the organism’s entire species
from becoming extinct in the event of a serious disease outbreak. An organism population with diverse
genetic variability has more chance of survival than one with more limited genetic variability.
BIO 1100, Non-Majors Biology
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Gametes (sperm and egg cells) do not undergo mitosis. Gametes undergo a process
called meiosis
UNIT x STUDY
GUIDE(Belk &
Maier, 2019), which is discussed in Chapter 7. Meiosis is referred to as reductional
Title division, in which one cell
divides into four cells that each contain half the number of chromosomes compared to the number contained
in the original cell before it divided. During meiosis, genetic information crosses over and aligns randomly on
the resulting chromosome and, therefore, produces cells that are not genetically identical. This allows for
diversity among sperm and eggs.
Cell division does not always happen as it should—sometimes mistakes occur. Think of it this way: If you
were to copy information from a note, you might make a mistake and copy down the wrong information. For
example, you may copy the word not instead of note. Mistakes similar to this sometimes occur when cells
undergo mitosis or meiosis. When such a mistake occurs during cell division, it is referred to as a mutation
(Belk & Maier, 2019). Mutation is random and is one of the forces that drive evolution. Mutations can be
detrimental because, when a mistake occurs,, something may go wrong. However, some mutations do not
matter, some can be good, but, as mentioned, some mutations can result in detrimental situations, such as
the development of cancer.
Not all cancer results from mutated information in DNA. Some forms of cancer—as well as many other
characteristics—are passed to us from our parents. In Chapter 8, “Does Testing Save Lives?” you will learn
about the basic concepts of the inheritance of traits and how genes interact with the environment. You will
also learn to compute possible offspring outcomes using Punnett squares.
Our knowledge about genes and genetic information began when a brilliant Austrian monk, Gregor Mendel,
conducted experiments on pea plants. Mendel conducted his work around 1855-1865. He published his
findings in 1865, but his work was not appreciated—perhaps not understood?—until after the turn of the
century. Mendel died in 1884, and unfortunately, the abbot who succeeded him burned all of Mendel’s
papers; this was a great loss to science. However, Mendel’s work was rediscovered by scientists in the early
1900s (Belk & Maier, 2019).
Mendel figured out that the “factors” he was studying came in pairs. Since then, Francis Watson and James
Crick have been credited with the discovery of the structure of DNA with the help of Rosalind Franklin, who
used X-ray crystallography to capture images of DNA (Science History Institute, n.d.). Our knowledge of
genetics continues to increase. For example, we now know that chromosomes do indeed come in pairs,
something Mendel only suspected.
One aspect that determines the success of a scientific study is using the right subject. Mendel did just that.
He studied pea plants, which reproduce sexually. Mendel was able to control the plants’ reproduction by
removing the flowers’ reproductive
organs and fertilizing the plants
manually. What patience he must
have had! It is estimated that over
the course of his studies, Mendel
raised about 30,000 plants
(Biography, 2014).
Mendel observed that pea plants
had some traits that were “eitheror,” with only two alternatives. His
plant’s flowers were either purple
or white, the seeds were either
round or wrinkled, the seeds’ color Mendel’s seven traits
was either yellow or green, and so (Ruiz, 2006)
on. Mendel believed that heredity was carried from parents to offspring by “factors.” He observed that
traits, such as color, were either one or the other, never something in between. What does this tell you
about the “factors”?”
Mendel bred his peas until they either produced all of one trait or the other, such as all yellow seeds or all
green seeds. Once he was sure that the plants were either one trait or the other, yellow or green, he crossed
them, breeding, for example, yellow-seeded plants with green-seeded plants. He called the purebred plants
the P generation (for parental). He discovered that all the offspring looked the same. For example, crossing
BIO 1100, Non-Majors Biology
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yellow -seeded plants with green-seeded plants all resulted in yellow-colored seed
OneGUIDE
would think
UNIT plants.
x STUDY
that the offspring of the yellow-seeded and green-seeded plants would be halfTitle
yellow and half green, or a
mixture of the colors, but they were not. Mendel called this generation of plants the F1 generation, “F”
standing for filial, Latin for daughter.
Therefore, if you cross an organism that is purebred for a specific trait with another purebred organism with a
different allele for that trait, the first generation is called the F1 generation. All of the offspring in the F1
generation will have the phenotype of the dominant allele, and they will all be heterozygous in their genotype.
In your assignment for this unit, you are asked about crossing F1 organisms with other F1 organisms. This
time you will get different results, and the second generation is called the F2 generation. You will determine
the phenotypes and the genotypes of the F2 generation.
Why did Mendel not use people or elephants or giant sequoia trees? Is it ethical to pick traits from two people
and have them mate to determine the offspring? How much space would it take to study elephants or giant
sequoia trees? How much food would it take to feed people and elephants? As mentioned, Mendel chose his
subject wisely—not only could he easily manipulate fertilization of his plants, but he could also eat them, and
they did not require a tremendous amount of space or resources.
The most important characteristic of Mendel’s peas was mentioned earlier—that Mendel was able to
manipulate the fertilization of the pea plants (Belk & Maier, 2019). Significant characteristics of the pea plant
include these characteristics:








it can be self-fertilized or cross-fertilized,
it is easy to grow and cultivate,
each pea is a different fertilization event,
it has seven characteristics that have only two phenotypes (dominant/recessive),
it can be true bred (has a certain phenotype and only produces offspring with the same phenotype),
it is an annual (life cycle of growing from a seed to producing seeds is one year and then dies),
it is diploid (contains two sets of chromosomes—one from each parent), and
it relies on sexual reproduction.
Mendel was also fortunate that each of the seven traits he studied are on separate chromosomes. For
example, if flower color and seed shape had been on the same chromosome, he might not have figured out
independent assortment, because color and wrinkling would have gone together instead of being independent
(Belk & Maier, 2019).
The genetic composition of an individual is known as the person’s genotype. The genes then result in various
physical traits known as phenotypes. Variations of genes are called alleles. An organism that is produced by
sexual reproduction receives one gene from each parent. When an organism receives the same allele from
each parent, it is said to be homozygous for that trait. When the organism receives a different allele from each
parent, it is heterozygous (Belk & Maier, 2019). So, which trait “wins out” and shows through?
Human and many other organisms’ genetics are not simple. Many characteristics and traits are determined by
multiple genes a …
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