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  # Download 11–2 Probability and Punnett Squares
  
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  ```0262_0280_bi_c07_te
  3/8/06
  10:52 AM
  Page 267
  11–2 Probability and Punnett Squares
  Section 11–2
  1 FOCUS
  Objectives
  W
  henever Mendel performed a cross with pea plants, he
  carefully categorized and counted the many offspring.
  Every time Mendel repeated a particular cross, he obtained
  similar results. For example, whenever Mendel crossed two
  plants that were hybrid for stem height (Tt), about three fourths
  of the resulting plants were tall and about one fourth were
  short. Mendel realized that the principles of probability could be
  used to explain the results of genetic crosses.
  Genetics and Probability
  The likelihood that a particular event will occur is called
  probability. As an example of probability, consider an ordinary
  event like the coin flip shown in Figure 11– 6. There are two
  possible outcomes: The coin may land heads up or tails up. The
  chances, or probabilities, of either outcome are equal. Therefore,
  the probability that a single coin flip will come up heads is 1
  chance in 2. This is 1/2, or 50 percent.
  If you flip a coin three times in a row, what is the probability
  that it will land heads up every time? Because each coin flip is
  an independent event, the probability of each coin’s
  landing heads up is 1/2. Therefore, the probability of
  flipping three heads in a row is:
  ⫻
  ⫻
  Key Concepts
  • How do geneticists use the
  principles of probability?
  • How do geneticists use
  Punnett squares?
  11.2.1 Explain how geneticists use
  the principles of probability.
  11.2.2 Describe how geneticists use
  Punnett squares.
  Vocabulary
  probability
  Punnett square
  homozygous
  heterozygous
  phenotype
  genotype
  Reading Strategy:
  Building Vocabulary Before
  you read, preview the list of new
  vocabulary words. Predict the
  relationship between phenotype
  and genotype. As you read,
  check to see if your predictions
  were correct.
  = .
  As you can see, you have 1 chance in 8 of flipping
  heads three times in a row. That the individual probabilities are multiplied together illustrates an important
  point—past outcomes do not affect future ones.
  How is coin flipping relevant to genetics? The way
  in which alleles segregate is completely random, like a
  coin flip.
  The principles of probability can be
  used to predict the outcomes of genetic crosses.
  Vocabulary Preview
  Ask: What suffix do the words
  homozygous and heterozygous
  share? (-zygous) Tell students that
  -zygous means “yoked” or “joined,”
  and the prefix homo- means “same.”
  Also explain that a homozygous
  organism has two identical alleles for
  a certain gene. Ask: If hetero- means
  “other,” what does heterozygous
  describe? (An organism with two different alleles for a gene)
  Reading Strategy
  Encourage students to write down
  the main headings of the section
  before they begin reading. Tell them
  to leave room below each heading to
  record important ideas as they read.
  2 INSTRUCT
  Genetics and
  Probability
  What is the probability that a tossed coin will
  come up tails twice in a row?
  Make Connections
  왘
  Figure 11–6 The mathematical concept
  of probability allows you to calculate the
  likelihood that a particular event will occur.
  Predicting What is the probability that the
  coin will land heads up?
  SECTION RESOURCES
  • Teaching Resources, Lesson Plan 11–2,
  Adapted Section Summary 11–2, Adapted
  Sav11–2,
  Worksheets 11–2, Section Summary
  e
  e
  Worksheets 11–2, Section Review 11–2,
  Enrichment
  • Reading and Study Workbook A, Section 11–2
  • Adapted Reading and Study Workbook B,
  Section 11–2
  • iText, Section 11–2
  • Transparencies Plus, Section 11–2
  Tim
  Technology:
  r
  Print:
  Mathematics Give pairs of students
  a paper bag that has 4 items that are
  identical except for color. The items
  should be the same shape and size.
  Ask: What is the probability of picking a red item? (1/4 or 25 percent)
  Of picking a red item two times in
  a row? (1/4 ⫻ 1/4 ⫽ 1/16) Then,
  instruct students to pick an item from
  the bag 20 times, then 50 times. Ask:
  Did your results equal your calculated probabilities? (The more times
  students pick from the bag, the closer
  their actual results will be to the predicted probability.)
  Answers to . . .
  1/4 or 25 percent
  Figure 11–6 1/2 or 50 percent
  Introduction to Genetics
  267
  0262_0280_bi_c07_te
  3/8/06
  10:52 AM
  Page 268
  Father’s genotype
  is dd (2 even digits)
  11–2 (continued)
  Punnett Squares
  4638
  How are dimples inherited?
  Materials copy of page from telephone book,
  Objective Students will be able to
  conclude how dimples are inherited.
  calculator
  Skills Focus Applying Concepts,
  Drawing Conclusions
  Materials copy of page from telephone book, calculator
  Time 15 minutes
  Advance Prep Photocopy several
  pages from a telephone book.
  Strategies
  • Demonstrate the use of a 4-digit
  number to represent the genotypes of the parents in a genetic
  cross.
  • Show students how to set up and
  use Punnett squares, if necessary.
  Expected Outcomes Students
  will determine the probability of
  having a child with dimples based
  on the genotypes of the parents.
  Calculated probabilities will vary
  depending on the genotypes of the
  parents.
  Analyze and Conclude
  1. Class averages will vary but will
  usually be close to 75 percent dimples, the result of a cross between
  two heterozygotes.
  2. 100 percent because the allele for
  dimples (D) is a dominant allele.
  1. Write the last 4 digits of any telephone number.
  These 4 random digits represent the alleles of a
  gene that determines whether a person will have
  dimples. Odd digits represent the allele for the
  dominant trait of dimples. Even digits stand for the
  allele for the recessive trait of no dimples.
  2. Use the first 2 digits to represent a certain father’s
  genotype. Use the symbols D and d to write his
  genotype, as shown in the example.
  3. Use the last 2 digits the same way to find the
  mother’s genotype. Write her genotype.
  Procedure
  Probability and
  Segregation
  Address Misconceptions
  Beginning genetics students often
  misinterpret probable genotypic and
  phenotypic ratios as actual numbers
  of offspring. Provide opportunities to
  calculate “actual” ratios using F2 corn
  cobs or experimental data. Students
  should set up Punnett squares and
  compare the predicted ratios with
  the “actual” ratios.
  268
  Chapter 11
  Mother’s genotype
  is Dd (1 even digit
  and 1 odd digit)
  4. Use Figure 11–7 as an example to construct a
  Punnett square for the cross of these parents. Then,
  using the Punnett square, determine the probability that their child will have dimples.
  5. Determine the class average of the percent of
  children with dimples.
  Analyze and Conclude
  1. Applying Concepts How does the class average
  compare with the result of a cross of two heterozygous parents?
  2. Drawing Conclusions What percentage of the
  children will be expected to have dimples if one
  parent is homozygous for dimples (DD) and the
  other is heterozygous (Dd)?
  Punnett Squares
  Tt
  Tt
  T
  t
  T
  TT 25%
  Tt 25%
  t
  Tt 25%
  tt 25%
  왖
  Figure 11–7
  The principles of
  probability can be used to predict the
  outcomes of genetic crosses. This
  Punnett square shows the probability
  of each possible outcome of a cross
  between hybrid tall (Tt) pea plants.
  The gene combinations that might result from a genetic
  cross can be determined by drawing a diagram known as
  a Punnett square. The Punnett square in Figure 11–7
  shows one of Mendel’s segregation experiments. The types
  of gametes produced by each F1 parent are shown along
  the top and left sides of the square. The possible gene
  combinations for the F2 offspring appear in the four
  boxes that make up the square. The letters in the
  Punnett square represent alleles. In this example, T
  represents the dominant allele for tallness and t represents the recessive allele for shortness.
  Punnett
  squares can be used to predict and compare the
  genetic variations that will result from a cross.
  Organisms that have two identical alleles for a particular trait—TT or tt in this example—are said to be
  homozygous (hoh-moh-ZY-gus). Organisms that have
  two different alleles for the same trait are heterozygous
  (het-ur-oh-ZY-gus). Homozygous organisms are truebreeding for a particular trait. Heterozygous organisms
  are hybrid for a particular trait.
  All of the tall plants have the same phenotype, or
  physical characteristics. They do not, however, have the
  same genotype, or genetic makeup. The genotype of one
  third of the tall plants is TT, while the genotype of two
  thirds of the tall plants is Tt. The plants in Figure 11–8
  have the same phenotype but different genotypes.
  UNIVERSAL ACCESS
  Inclusion/Special Needs
  Give students additional opportunities to practice
  calculating probabilities by making available a
  “probabilities kit.” In this “kit,” provide coins and
  a grab bag with colored beads, colored sticks, or
  any other manipulative that differs only in color.
  You might have these students pair up with
  advanced students to predict probabilities and
  observe the outcomes.
  Less Proficient Readers
  Challenge students to write an instructional manual for using Punnett squares. Students should
  include a labeled diagram of a Punnett square in
  their manual, as well as step-by-step directions on
  how to use one and why Punnett squares are useful tools for geneticists.
  0262_0280_bi_c07_te
  3/8/06
  10:52 AM
  Page 269
  Probabilities Predict
  Averages
  Probability and Segregation
  Look again at Figure 11–7. One fourth (1/4) of the F2 plants have
  two alleles for tallness (TT); 2/4, or 1/2, of the F2 plants have one
  allele for tallness and one allele for shortness (Tt). Because the
  allele for tallness is dominant over the allele for shortness, 3/4
  of the F2 plants should be tall. Overall, there are 3 tall plants
  for every 1 short plant in the F2 generation. Thus, the ratio of
  tall plants to short plants is 3 : 1. This assumes, of course, that
  Mendel’s model of segregation is correct.
  Did the data from Mendel’s experiments fit his model? Yes.
  The predicted ratio—3 dominant to 1 recessive—showed up
  consistently, indicating that Mendel’s assumptions about
  segregation had been correct. For each of his seven crosses,
  about 3/4 of the plants showed the trait controlled by the
  dominant allele. About 1/4 showed the trait controlled by the
  recessive allele. Segregation did indeed occur according to
  Mendel’s model.
  Probabilities Predict Averages
  Probabilities predict the average outcome of a large number of
  events. However, probability cannot predict the precise outcome
  of an individual event. If you flip a coin twice, you are likely to
  get one head and one tail. However, you might also get two
  heads or two tails. To be more likely to get the expected 50 : 50
  ratio, you would have to flip the coin many times.
  The same is true of genetics. The larger the number of offspring, the closer the resulting numbers will get to expected
  values. If an F1 generation contains just three or four offspring, it
  may not match Mendelian predicted ratios. When an F1 generation contains hundreds or thousands of individuals, however, the
  ratios usually come very close to matching expectations.
  Build Science Skills
  Designing Experiments Give students a coin or a bag with 2 or 3
  beads that differ in color. Ask them to
  design an experiment to show that
  probabilities cannot predict the outcome of an individual event.
  3 ASSESS
  TT
  Homozygous
  Tt
  Heterozygous
  Figure 11–8 Although these
  plants have different genotypes
  (TT and Tt), they have the same
  phenotype (tall). Predicting If you
  crossed these two plants, would their
  offspring be tall or short?
  Key Concept How are the
  principles of probability used to
  predict the outcomes of genetic
  crosses?
  2.
  Key Concept How are
  Punnett squares used?
  3. What is probability?
  4. Define the terms genotype and
  phenotype.
  Assign students different traits in
  peas. Then, instruct them to set up a
  Punnett square to show the cross
  between two heterozygous pea
  plants for their trait. Students should
  give both the genotypic and phenotypic ratio of the offspring.
  Reteach
  Give student pairs a list of genetic
  crosses between parents of various
  genotypes. Instruct pairs to use
  Punnett squares to show the possible
  outcomes of the crosses.
  11–2 Section Assessment
  1.
  Evaluate Understanding
  Drawing Punnett Squares
  Imagine that you came upon
  a tall pea plant similar to
  those Mendel used in his
  experiments. How could you
  determine the plant’s genotype with respect to height?
  Draw two Punnett squares to
  show your answer.
  5. Critical Thinking Problem
  Solving An F1 plant that is
  homozygous for shortness is
  crossed with a heterozygous F1
  plant. What is the probability that
  a seed from the cross will produce a tall plant? Use a Punnett
  square to explain your answer
  and to compare the probable
  genetic variations in the F2
  plants.
  The genotype of the tall pea plant
  is determined by allowing the
  plant to self-pollinate. If the plant
  is heterozygous, there is a 25 percent chance that an offspring will
  be short. If the plant is homozygous, then all offspring will be tall.
  Students should draw Punnett
  squares to show both possibilities.
  If your class subscribes to the iText,
  use it to review the Key Concepts in
  Section 11–2.
  11–2 Section Assessment
  1. The way in which the alleles segregate is random, and probability allows the calculation
  of the likelihood that a particular allele combination will occur in offspring.
  2. To predict and compare the genetic variations that will result from a cross
  3. The likelihood that a particular event will
  occur
  4. Genotype: actual alleles present for a trait, or
  genetic makeup; phenotype: visible expression of the alleles, or physical characteristics
  5. 50 percent; Punnett square:
  T
  t
  t
  Tt
  tt
  t
  Tt
  tt
  Answer to . . .
  Figure 11–8 All of the offspring
  would be tall.
  Introduction to Genetics
  269
  ```
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  # Download 11–2 Probability and Punnett Squares
  
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  Was this document useful for you?
  Thank you for your participation!
  
  * Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
  
  Transcript
  ```0262_0280_bi_c07_te
  3/8/06
  10:52 AM
  Page 267
  11–2 Probability and Punnett Squares
  Section 11–2
  1 FOCUS
  Objectives
  W
  henever Mendel performed a cross with pea plants, he
  carefully categorized and counted the many offspring.
  Every time Mendel repeated a particular cross, he obtained
  similar results. For example, whenever Mendel crossed two
  plants that were hybrid for stem height (Tt), about three fourths
  of the resulting plants were tall and about one fourth were
  short. Mendel realized that the principles of probability could be
  used to explain the results of genetic crosses.
  Genetics and Probability
  The likelihood that a particular event will occur is called
  probability. As an example of probability, consider an ordinary
  event like the coin flip shown in Figure 11– 6. There are two
  possible outcomes: The coin may land heads up or tails up. The
  chances, or probabilities, of either outcome are equal. Therefore,
  the probability that a single coin flip will come up heads is 1
  chance in 2. This is 1/2, or 50 percent.
  If you flip a coin three times in a row, what is the probability
  that it will land heads up every time? Because each coin flip is
  an independent event, the probability of each coin’s
  landing heads up is 1/2. Therefore, the probability of
  flipping three heads in a row is:
  ⫻
  ⫻
  Key Concepts
  • How do geneticists use the
  principles of probability?
  • How do geneticists use
  Punnett squares?
  11.2.1 Explain how geneticists use
  the principles of probability.
  11.2.2 Describe how geneticists use
  Punnett squares.
  Vocabulary
  probability
  Punnett square
  homozygous
  heterozygous
  phenotype
  genotype
  Reading Strategy:
  Building Vocabulary Before
  you read, preview the list of new
  vocabulary words. Predict the
  relationship between phenotype
  and genotype. As you read,
  check to see if your predictions
  were correct.
  = .
  As you can see, you have 1 chance in 8 of flipping
  heads three times in a row. That the individual probabilities are multiplied together illustrates an important
  point—past outcomes do not affect future ones.
  How is coin flipping relevant to genetics? The way
  in which alleles segregate is completely random, like a
  coin flip.
  The principles of probability can be
  used to predict the outcomes of genetic crosses.
  Vocabulary Preview
  Ask: What suffix do the words
  homozygous and heterozygous
  share? (-zygous) Tell students that
  -zygous means “yoked” or “joined,”
  and the prefix homo- means “same.”
  Also explain that a homozygous
  organism has two identical alleles for
  a certain gene. Ask: If hetero- means
  “other,” what does heterozygous
  describe? (An organism with two different alleles for a gene)
  Reading Strategy
  Encourage students to write down
  the main headings of the section
  before they begin reading. Tell them
  to leave room below each heading to
  record important ideas as they read.
  2 INSTRUCT
  Genetics and
  Probability
  What is the probability that a tossed coin will
  come up tails twice in a row?
  Make Connections
  왘
  Figure 11–6 The mathematical concept
  of probability allows you to calculate the
  likelihood that a particular event will occur.
  Predicting What is the probability that the
  coin will land heads up?
  SECTION RESOURCES
  • Teaching Resources, Lesson Plan 11–2,
  Adapted Section Summary 11–2, Adapted
  Sav11–2,
  Worksheets 11–2, Section Summary
  e
  e
  Worksheets 11–2, Section Review 11–2,
  Enrichment
  • Reading and Study Workbook A, Section 11–2
  • Adapted Reading and Study Workbook B,
  Section 11–2
  • iText, Section 11–2
  • Transparencies Plus, Section 11–2
  Tim
  Technology:
  r
  Print:
  Mathematics Give pairs of students
  a paper bag that has 4 items that are
  identical except for color. The items
  should be the same shape and size.
  Ask: What is the probability of picking a red item? (1/4 or 25 percent)
  Of picking a red item two times in
  a row? (1/4 ⫻ 1/4 ⫽ 1/16) Then,
  instruct students to pick an item from
  the bag 20 times, then 50 times. Ask:
  Did your results equal your calculated probabilities? (The more times
  students pick from the bag, the closer
  their actual results will be to the predicted probability.)
  Answers to . . .
  1/4 or 25 percent
  Figure 11–6 1/2 or 50 percent
  Introduction to Genetics
  267
  0262_0280_bi_c07_te
  3/8/06
  10:52 AM
  Page 268
  Father’s genotype
  is dd (2 even digits)
  11–2 (continued)
  Punnett Squares
  4638
  How are dimples inherited?
  Materials copy of page from telephone book,
  Objective Students will be able to
  conclude how dimples are inherited.
  calculator
  Skills Focus Applying Concepts,
  Drawing Conclusions
  Materials copy of page from telephone book, calculator
  Time 15 minutes
  Advance Prep Photocopy several
  pages from a telephone book.
  Strategies
  • Demonstrate the use of a 4-digit
  number to represent the genotypes of the parents in a genetic
  cross.
  • Show students how to set up and
  use Punnett squares, if necessary.
  Expected Outcomes Students
  will determine the probability of
  having a child with dimples based
  on the genotypes of the parents.
  Calculated probabilities will vary
  depending on the genotypes of the
  parents.
  Analyze and Conclude
  1. Class averages will vary but will
  usually be close to 75 percent dimples, the result of a cross between
  two heterozygotes.
  2. 100 percent because the allele for
  dimples (D) is a dominant allele.
  1. Write the last 4 digits of any telephone number.
  These 4 random digits represent the alleles of a
  gene that determines whether a person will have
  dimples. Odd digits represent the allele for the
  dominant trait of dimples. Even digits stand for the
  allele for the recessive trait of no dimples.
  2. Use the first 2 digits to represent a certain father’s
  genotype. Use the symbols D and d to write his
  genotype, as shown in the example.
  3. Use the last 2 digits the same way to find the
  mother’s genotype. Write her genotype.
  Procedure
  Probability and
  Segregation
  Address Misconceptions
  Beginning genetics students often
  misinterpret probable genotypic and
  phenotypic ratios as actual numbers
  of offspring. Provide opportunities to
  calculate “actual” ratios using F2 corn
  cobs or experimental data. Students
  should set up Punnett squares and
  compare the predicted ratios with
  the “actual” ratios.
  268
  Chapter 11
  Mother’s genotype
  is Dd (1 even digit
  and 1 odd digit)
  4. Use Figure 11–7 as an example to construct a
  Punnett square for the cross of these parents. Then,
  using the Punnett square, determine the probability that their child will have dimples.
  5. Determine the class average of the percent of
  children with dimples.
  Analyze and Conclude
  1. Applying Concepts How does the class average
  compare with the result of a cross of two heterozygous parents?
  2. Drawing Conclusions What percentage of the
  children will be expected to have dimples if one
  parent is homozygous for dimples (DD) and the
  other is heterozygous (Dd)?
  Punnett Squares
  Tt
  Tt
  T
  t
  T
  TT 25%
  Tt 25%
  t
  Tt 25%
  tt 25%
  왖
  Figure 11–7
  The principles of
  probability can be used to predict the
  outcomes of genetic crosses. This
  Punnett square shows the probability
  of each possible outcome of a cross
  between hybrid tall (Tt) pea plants.
  The gene combinations that might result from a genetic
  cross can be determined by drawing a diagram known as
  a Punnett square. The Punnett square in Figure 11–7
  shows one of Mendel’s segregation experiments. The types
  of gametes produced by each F1 parent are shown along
  the top and left sides of the square. The possible gene
  combinations for the F2 offspring appear in the four
  boxes that make up the square. The letters in the
  Punnett square represent alleles. In this example, T
  represents the dominant allele for tallness and t represents the recessive allele for shortness.
  Punnett
  squares can be used to predict and compare the
  genetic variations that will result from a cross.
  Organisms that have two identical alleles for a particular trait—TT or tt in this example—are said to be
  homozygous (hoh-moh-ZY-gus). Organisms that have
  two different alleles for the same trait are heterozygous
  (het-ur-oh-ZY-gus). Homozygous organisms are truebreeding for a particular trait. Heterozygous organisms
  are hybrid for a particular trait.
  All of the tall plants have the same phenotype, or
  physical characteristics. They do not, however, have the
  same genotype, or genetic makeup. The genotype of one
  third of the tall plants is TT, while the genotype of two
  thirds of the tall plants is Tt. The plants in Figure 11–8
  have the same phenotype but different genotypes.
  UNIVERSAL ACCESS
  Inclusion/Special Needs
  Give students additional opportunities to practice
  calculating probabilities by making available a
  “probabilities kit.” In this “kit,” provide coins and
  a grab bag with colored beads, colored sticks, or
  any other manipulative that differs only in color.
  You might have these students pair up with
  advanced students to predict probabilities and
  observe the outcomes.
  Less Proficient Readers
  Challenge students to write an instructional manual for using Punnett squares. Students should
  include a labeled diagram of a Punnett square in
  their manual, as well as step-by-step directions on
  how to use one and why Punnett squares are useful tools for geneticists.
  0262_0280_bi_c07_te
  3/8/06
  10:52 AM
  Page 269
  Probabilities Predict
  Averages
  Probability and Segregation
  Look again at Figure 11–7. One fourth (1/4) of the F2 plants have
  two alleles for tallness (TT); 2/4, or 1/2, of the F2 plants have one
  allele for tallness and one allele for shortness (Tt). Because the
  allele for tallness is dominant over the allele for shortness, 3/4
  of the F2 plants should be tall. Overall, there are 3 tall plants
  for every 1 short plant in the F2 generation. Thus, the ratio of
  tall plants to short plants is 3 : 1. This assumes, of course, that
  Mendel’s model of segregation is correct.
  Did the data from Mendel’s experiments fit his model? Yes.
  The predicted ratio—3 dominant to 1 recessive—showed up
  consistently, indicating that Mendel’s assumptions about
  segregation had been correct. For each of his seven crosses,
  about 3/4 of the plants showed the trait controlled by the
  dominant allele. About 1/4 showed the trait controlled by the
  recessive allele. Segregation did indeed occur according to
  Mendel’s model.
  Probabilities Predict Averages
  Probabilities predict the average outcome of a large number of
  events. However, probability cannot predict the precise outcome
  of an individual event. If you flip a coin twice, you are likely to
  get one head and one tail. However, you might also get two
  heads or two tails. To be more likely to get the expected 50 : 50
  ratio, you would have to flip the coin many times.
  The same is true of genetics. The larger the number of offspring, the closer the resulting numbers will get to expected
  values. If an F1 generation contains just three or four offspring, it
  may not match Mendelian predicted ratios. When an F1 generation contains hundreds or thousands of individuals, however, the
  ratios usually come very close to matching expectations.
  Build Science Skills
  Designing Experiments Give students a coin or a bag with 2 or 3
  beads that differ in color. Ask them to
  design an experiment to show that
  probabilities cannot predict the outcome of an individual event.
  3 ASSESS
  TT
  Homozygous
  Tt
  Heterozygous
  Figure 11–8 Although these
  plants have different genotypes
  (TT and Tt), they have the same
  phenotype (tall). Predicting If you
  crossed these two plants, would their
  offspring be tall or short?
  Key Concept How are the
  principles of probability used to
  predict the outcomes of genetic
  crosses?
  2.
  Key Concept How are
  Punnett squares used?
  3. What is probability?
  4. Define the terms genotype and
  phenotype.
  Assign students different traits in
  peas. Then, instruct them to set up a
  Punnett square to show the cross
  between two heterozygous pea
  plants for their trait. Students should
  give both the genotypic and phenotypic ratio of the offspring.
  Reteach
  Give student pairs a list of genetic
  crosses between parents of various
  genotypes. Instruct pairs to use
  Punnett squares to show the possible
  outcomes of the crosses.
  11–2 Section Assessment
  1.
  Evaluate Understanding
  Drawing Punnett Squares
  Imagine that you came upon
  a tall pea plant similar to
  those Mendel used in his
  experiments. How could you
  determine the plant’s genotype with respect to height?
  Draw two Punnett squares to
  show your answer.
  5. Critical Thinking Problem
  Solving An F1 plant that is
  homozygous for shortness is
  crossed with a heterozygous F1
  plant. What is the probability that
  a seed from the cross will produce a tall plant? Use a Punnett
  square to explain your answer
  and to compare the probable
  genetic variations in the F2
  plants.
  The genotype of the tall pea plant
  is determined by allowing the
  plant to self-pollinate. If the plant
  is heterozygous, there is a 25 percent chance that an offspring will
  be short. If the plant is homozygous, then all offspring will be tall.
  Students should draw Punnett
  squares to show both possibilities.
  If your class subscribes to the iText,
  use it to review the Key Concepts in
  Section 11–2.
  11–2 Section Assessment
  1. The way in which the alleles segregate is random, and probability allows the calculation
  of the likelihood that a particular allele combination will occur in offspring.
  2. To predict and compare the genetic variations that will result from a cross
  3. The likelihood that a particular event will
  occur
  4. Genotype: actual alleles present for a trait, or
  genetic makeup; phenotype: visible expression of the alleles, or physical characteristics
  5. 50 percent; Punnett square:
  T
  t
  t
  Tt
  tt
  t
  Tt
  tt
  Answer to . . .
  Figure 11–8 All of the offspring
  would be tall.
  Introduction to Genetics
  269
  ```
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distilabel_metadata.role: user
distilabel_metadata.raw_output_q_a_detector_0: The provided text is an educational excerpt from a biology textbook, specifically discussing the application of probability in genetics and the use of Punnett squares. The text includes several questions and activities designed to engage students in understanding genetic principles.
  
  1. **Description of the Document:**
     - The document covers the concepts of probability in genetics, Punnett squares, and the terms homozygous and heterozygous.
     - It includes questions and activities to help students understand and apply these concepts.
  
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  **Label: multiple-question**