FINAL 07 2020, questions and answers PDF

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Module_8_ Ch_14...

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6/13/2020

Module #8: Ch 14

Module #8: Ch 14 Due: 11:59pm on Thursday, July 1, 2021 You will receive no credit for items you complete after the assignment is due. Grading Policy

Activity: The Principle of Independent Assortment

Click here to view this animation. Then answer the questions.

Part A What process is responsible for the independent assortment of alleles?

Hint 1. How are traits inherited under the theory of blending inheritance?

ANSWER: Mitosis DNA replication. Cytokinesis. Meiosis.

Correct The role of meiosis is to separate homologous chromosomes and their respective alleles, which are assorted in an independent manner.

Part B How do cells acquire homologous chromosome pairs that carry the alleles that are independently assorted? ANSWER:

Fusion of gametes Meiosis Mitosis DNA replication

Correct During fertilization, gametes bring together homologous chromosomes to generate a diploid individual.

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Module #8: Ch 14

Which of the following statements most accurately describes the process of independent assortment? ANSWER:

Alleles found on separate chromosomes segregate based upon their origin. Genes located on the same chromosome assort as an independent unit. Alleles of different genes segregate from one another in a random manner. Dominant alleles segregate with recessive alleles.

Correct The random distribution of alleles is required for independent assortment.

Part D True or false? The principle of independent assortment is best illustrated by events that take place during metaphase II, during which sister chromatids segregate independently of each other.

Hint 1. Consider which meiotic division involves the segregation of alleles of different genes.

ANSWER:

True False

Correct The principle of independent assortment is best illustrated by events that take place during metaphase I, during which nonhomologous chromosomes segregate independently of each other.

Part E How many genetically unique types of gametes could be produced by an individual with the genotype RrYY?

Hint 1. Assume that the alleles assort independently of each other during gamete formation.

ANSWER:

Eight One Two Three

Correct The gametes would be either RY or rY.

Part F Which of the following parental genotypes would yield a 1:1:1:1 phenotypic ratio in the offspring?

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Hint 1. Use a Punnett square to diagram the genotypic and phenotypic ratios that would result from the crosses.

ANSWER: aaBb, aabb AaBb, aabb AaBb, AaBb aaBb, AaBb

Correct The offspring of these parents would have a phenotypic ratio of 1:1:1:1.

Determining Genotype: Pea Pod Color A botanist has acquired a group of sweet pea plants. All of the plants have yellow pea pods (the recessive trait), except for one, which has green pea pods (the dominant trait). Pea pod color is a trait caused by a single gene. In this tutorial, you will determine how the botanist can identify the genotype of the green pea pod and how this relates to Mendel’s laws and meiosis.

Part A - Identifying the genotype How could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous?

Hint 1. Definitions of genotype, homozygous, and heterozygous Genotype: the genetic makeup (allele composition) of one or more genes in an organism Homozygous: having two identical alleles for a given gene Heterozygous: having two different alleles for a given gene Hint 2. What possible genotypes could the green-pod plant have? Which of the following genotypes could the green-pod plant have? (G is the symbol for the green-pod allele; g is the symbol for the yellow-pod allele.) Select all that apply. ANSWER:

GG Gg gg

ANSWER: Cross the green-pod plant with a yellow-pod plant. Self-pollinate the green-pod plant. Cross the green-pod plant with another green-pod plant.

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Module #8: Ch 14

Correct A cross between a plant of unknown genotype and one that is known to be homozygous recessive is called a test cross because the recessive homozygote tests whether there are any recessive alleles in the unknown. Because the recessive homozygote will contribute an allele for the recessive characteristic to each offspring, the second allele (from the unknown genotype) will determine the offspring’s phenotype.

Part B - Diagramming a cross using a Punnett square Punnett squares can be used to predict the two possible outcomes of the botanist’s test cross. The Punnett square on the left shows the predicted result if the unknown plant is homozygous (GG); the Punnett square on the right shows the predicted result if the unknown plant is heterozygous (Gg). Drag the labels to the correct locations on the Punnett squares. (G is the symbol for the green-pod allele and g is the symbol for the yellow-pod allele.) You can use a label once, more than once, or not at all.

Hint 1. How to create a Punnett square Follow these steps to create a Punnett square: 1. 2. 3. 4. 5.

Determine the possible gametes that each parent could produce. (Remember that a gamete will have one allele for a given gene.) For one parent, write the allele for each gamete along the top of the square. For the other parent, write the allele for each gamete down the left side of the square. Copy the alleles from the top into the boxes beneath them. Copy the alleles from the left into the boxes to their right. Each of the boxes in the completed Punnett square represents the likelihood that one of the offspring will inherit that allele combination (or genotype).

Hint 2. What does a Punnett Square predict? Which statement correctly describes what a Punnett square predicts? ANSWER:

Each box represents one of the offspring that will definitely be produced from the cross. Each box represents the probability that any one offspring from the cross would have a particular genotype. Each box represents the alleles that will be found in one of the offspring from the cross.

ANSWER: Reset

gg

GG

g

G

Gg

g

G

Gg

Gg

Gg

Gg

Help

g

g

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Gg

Gg

gg

gg

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Module #8: Ch 14

Correct The genotypes in a Punnett square show all the possible combinations of alleles in offspring that could result from the particular cross. A Punnett square reveals the expected probabilities of each genotype among the offspring. For example, the Punnett square on the right reveals that there is a 50% chance that each offspring will have green pods and a 50% chance that each offspring will have yellow pods.

This botanist used the same logic to reach her conclusions as Mendel used in his experiments.

Part C - Relationship with Mendel’s findings Suppose that the botanist carried out the test cross described in Parts A and B and determined that the original green-pod plant was heterozygous (Gg). Whic of Mendel’s findings does her test cross illustrate?

Hint 1. Can you match the genetic principle to its description? Drag the terms on the left to the blanks on the right to match each description with the correct genetic principle. ANSWER:

Reset

Help

1. Genes that are located on the same chromosome tend to be inherited together. linkage 2. During gamete formation, the two alleles for each gene separate so that each gamete receives only one allele. law of segregation 3. During gamete formation, the alleles for one gene separate independently of the alleles for all other unlinked genes. law of independent assortment 4. Genes are located on chromosomes; the behavior of chromosomes during meiosis accounts for inheritance patterns. chromosome theory of inheritance

Hint 2. What Mendel did not know Mendel did not know that the “hereditary factors" he described were genes. He also did not know that genes are regions of chromosomes. It wasn’t until 1902, when Sutton and others proposed the chromosome theory of inheritance, that the relationship between Mendel’s “factors” and loci along chromosomes became known.

ANSWER:

law of segregation linkage law of independent assortment chromosome theory of inheritance

Correct The law of segregation states that the two alleles for a gene separate during gamete formation, and end up in different gametes. In the case of the heterozygous green-pod plant (Gg), one gamete will receive the dominant allele (G), and the other gamete will receive the recessive allele (g). The law of segregation accounts for the prediction that 50% of the offspring of the test cross will have green pods and 50% will have yellow pods.

Part D - Relationship of allele behavior to meiosis During which part of meiosis (meiosis I or meiosis II) do the two alleles of a gene separate? During which phase does the separation occur?

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State your answer as meiosis I or meiosis II followed by a comma and the name of the phase (for example, if your answer is meiosis II and metaphase, enter meiosis II, metaphase).

Hint 1. What are the key events of the stages of meiosis? Drag the words on the left to the appropriate blanks to complete the sentences on the right. ANSWER:

Reset

Help

1. During metaphase I , pairs of homologous chromosomes align in the center of the cell.

2. During telophase II , the separated chromatids elongate and (usually) cytokinesis occurs, forming four genetically distinct haploid daughter cells. 3. During anaphase I , homologous chromosomes separate by moving with the spindle microtubules toward the poles. 4. During prophase II , a spindle apparatus forms and individual chromosomes (each composed of sister chromatids) begin to move toward the center of the cell. 5. During prophase I , chiasmata form and crossing-over occurs.

6. During anaphase II , sister chromatids separate and move toward the poles.

7. During telophase I , the separated chromosomes cluster at the poles of the spindle and cytokinesis occurs, forming two daughter cells, each with a haploid set of replicated chromosomes. 8. During metaphase II , individual chromosomes (each composed of sister chromatids) align in the center of the cell.

Hint 2. Differences between meiosis I and meiosis II In meiosis I, the major events are the pairing of homologous chromosomes during prophase and their separation during anaphase. In meiosis II, the major event is the separation of sister chromatids during anaphase.

ANSWER: meiosis I, anaphase

Correct Alleles separate from one another during anaphase of meiosis I, when the homologous pairs of chromosomes separate.

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Incomplete Dominance and Codominance You are studying leaf development in a member of the mustard family. You identify several mutants of interest in this plant and make pure (true-breeding) lines of each mutant for further study.

Part A - Determining relationships between alleles You decide to conduct a genetic analysis of these mutant lines by crossing each with a pure wild-type line. The numbers in the F2 indicate the number of progeny in each phenotypic class.

From these results, determine the relationship between the mutant allele and its corresponding wild-type allele in each line. Label each mutant line with the best statement from the list below. Labels may be used once, more than once, or not at all.

Hint 1. How can I tell if an allele is dominant or recessive? You have obtained several colour variants of a berry that has a black wild-type phenotype. You have also determined that all the variants are due to different alleles of the same gene. Crosses between pure lines of the variants and wild type produce the following results:

Based on these results, select the four true statements from the list below. Check all that apply. ANSWER:

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Module #8: Ch 14 The green allele is dominant. The blue allele is recessive to the green allele. The blue allele is dominant to the wild-type allele. The blue allele is dominant to the green allele. The blue allele is recessive to the wild-type allele. The blue allele is recessive. The green allele is recessive to the blue allele. The green allele is recessive. The blue allele is dominant. The green allele is dominant to the wild-type allele. The green allele is dominant to the blue allele. The green allele is recessive to the wild-type allele.

Hint 2. How to determine allele relationships in cases with intermediate F1 phenotypes Some heterozygotes have a phenotype that is intermediate between the phenotypes of the two homozygotes. This situation is the result of incomplete dominance: Neither allele is completely dominant to the other.

ANSWER: Reset

The mutant allele is neither dominant nor completely recessive to its corresponding wild-type allele.

The mutant allele is recessive to its corresponding wildtype allele.

The mutant allele is dominant to its corresponding wildtype allele.

Help

The mutant allele is dominant to its corresponding wildtype allele.

The mutant allele is dominant to its corresponding wildtype allele.

The mutant allele is neither dominant nor completely recessive to its corresponding wild-type allele.

Correct An allele is never intrinsically "dominant" or "recessive." Instead, these terms describe a relationship between two alleles. This relationship is evaluated by examining a heterozygote: The allele that determines the phenotype of the heterozygote is dominant to the other (recessive) allele. Some heterozygotes have a phenotype that is intermediate between the phenotypes of the two homozygotes. This situation is the result of incomplete dominance: Neither allele is completely dominant to the other.

Part B - Crossing the forked and pale mutants

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You continue your genetic analysis by crossing the forked and pale mutant lines with each other. The leaves of the F1 are light green (intermediate between pale and wild-type leaves) and forked. The F2 has six phenotypic classes, as shown below. You designate the forked mutant allele as F (wild type = f+ ) and the pale mutant allele as p (wild type = P). 1. Consider the alleles for leaf colour first. Drag the white labels to the white targets to identify the genotype of each F2 class. Remember that p (the pale mutant allele) and P (the wild-type allele) are incompletely dominant to each other. 2. Consider the alleles for leaf shape next. Drag the blue labels to the blue targets to identify the genotype of each F2 class. Remember that F (the forked mutant allele) is dominant to f + (the wild-type allele). Labels may be used once, more than once, or not at all. For help getting started, see the hints.

Hint 1. Assigning genotypes for alleles that exhibit complete dominance In cases where an allele is completely dominant to another allele, only two phenotypic categories are present in a monohybrid cross: the dominant phenotype and the recessive one. Individuals with the dominant phenotype may have either of two genotypes: homozygous dominant or heterozygous. Because progeny in this category cannot be assigned a genotype on the basis of their phenotype alone, their genotypes are often summarized by writing the dominant allele followed by an underscore ( _ ), which indicates that either the dominant or the recessive allele may be present at the second position. Hint 2. How do I assign genotypes for alleles that exhibit incomplete dominance? Select the two phrases that correctly complete this sentence: In a monohybrid cross, incomplete dominance results in ANSWER: an F1 that matches the phenotype of one of the parental lines. an F1 that has an intermediate phenotype unlike that of either parental line. three phenotypic categories in the F2: homozygous dominant, heterozygous, and homozygous recessive progeny all have distinct phenotypes. two phenotypic categories in the F2: homozygous dominant and heterozygous progeny have the same phenotype, and homozygous recessive progeny have a different phenotype.

ANSWER: Reset

Help

PP

Pp

pp

P_

PP

F_

Pp

F_

pp

F_

PP

f+f+

Pp

f+f+

pp

f+f+

FF

Ff+

f+f+

F_

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Module #8: Ch 14

Correct Alleles P and p are incompletely dominant to each other. Therefore, each genotype has a distinct phenotype. That is why you are able to assign definite genotypes for leaf colour to each F2 plant. Allele F is dominant to f +. Therefore, you cannot be certain whether forked leaves are homozygous dominant or heterozygous. That is why you must assign the genotype F_ to the F2 plants in the top row. For the unforked leaves in the bottom row, you know they must be homozygous for the wildtype allele.

Part C - Crossing the forked and twist mutants You continue your analysis by crossing the forked and twist lines. Your results are as follows:

Which of the following statements best explains the outcome of this cross?

Hint 1. Distinguishing between incomplete dominance, codominance, and recombination Incomplete dominance and codominance apply to alleles at one locus. Recall that incomplete dominance means that a heterozygote has an intermediate phenotype. Codominance occurs when both alleles at a single locus express their phenotype simultaneously. Recombination applies to alleles at different loci. It occurs in a dihybrid when an allele at one locus is placed into a gamete with an allele at a second locus in a combination not present in either parental line. Hint 2. Why are there no wild-type progeny in the F2 of this cross? Why are there no wild-type progeny in the F2 of this cross? Check all that apply. ANSWER:

because the wild-type forked alleles in the F2 are hidden by recombination because there are no wild-type forked alleles in the F1 plants because there are no wild-type forked alleles in either parental line

ANSWER: The forked mutation is incompletely dominant to the twist mutation. The forked mutation and the twist mutation are codominant all...