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Goal 3 Concepts Of Biology

Expectation 3.3 The student will analyze how traits are inherited and passed on from one generation to another.

Indicator 3.3.2 The student will illustrate and explain how expressed traits are passed from parent to offspring.

Assessment Limits:

  • phenotypes (expression of inherited characteristics)
  • dominant and recessive traits
  • sex-linked traits (X-linked only; recessive phenotypes are more often expressed in the male)
  • genotypes (represented by heterozygous and homozygous pairs of alleles)
  • punnett square (use to predict and/or interpret the results of a genetic cross; translate genotypes into phenotypes - monohybrid only)
  • Pedigree (use to interpret patterns of inheritance within a family)

Brief Constructed Response (BCR) Item - Released in 2006

The length of a dog's tail is an inherited trait. The allele for short tails is dominant (T) over the allele for long tails (t). A dog breeder mates two short-tailed dogs (parents). One parent is homozygous and the other is heterozygous for this trait. A litter of twelve puppies, all with short tails, is produced (first generation). The breeder mates one of the first generation dogs with a short-tailed dog from another litter. A litter of ten puppies is produced (second generation). The breeder is surprised when one of the second generation puppies has a long tail.

Describe the genetic make-up of the parents and puppies that produced this inheritance pattern. In your response, be sure to

  • identify the genotype of the parents
  • use a Punnett square to show the possible genotypes of the first generation puppies
  • use a Punnett square to show the possible genotypes of the second generation puppies
  • identify the genotypic and phenotypic ratios of the first and second generation puppies
  • explain how a long-tailed dog can suddenly appear when all the other dog's were short-tailed

Write your answer in your Answer Book.

The following 4 Sample Student Responses represent a range of score points.

Sample Student Response #1

image of student response

Score for Sample Student Response #1: Rubric Score 4

Annotation: This response shows a full and complete understanding of the question. Pertinent details, including Punnett squares, fully labeled ratios, and genotypes, are integrated throughout the response. The student synthesizes a complete explanation about probability (if 2 heterozygous dogs create offspring, there is a 25% chance one will have a long tail because of how the alleles match up) in response to how a long-tailed dog can suddenly appear. (Compare to this Level 4 anchor paper.)


Sample Student Response #2

image of student response

Score for Sample Student Response #2: Rubric Score 1

Annotation: This response demonstrates some understanding of the question. The student correctly identifies the genotypes of the first generation parents (TT; Tt). Although the Punnett square for the first generation lacks the parents' genotypes, if the ones identified are used the Punnett square would be correct and does show some understanding. The overall lack of detail and missing genotypic and phenotypic ratios makes the support minimally effective. The statement explaining the appearance of a long-tailed puppy is incorrect (because the recessive gene is becoming more present throughout the generations).


Sample Student Response #3

image of student response

Score for Sample Student Response #3: Rubric Score 3

Annotation: This response demonstrates a good understanding of the question. All statements are correct, as are the Punnett squares. The genotypes of the parents are identified (TT and Tt). The accurate use of scientific terminology (not masked by dominant T; crossed) strengthens the response. The explanation for how a long-tailed puppy could appear in the second generation is well supported (both of the parents had to have been heterozygous; recessive t showed up in both parents and came together). While phenotypic ratios are provided for both generations (all the puppies were short tailed; 75% short tailed, 25% long tailed), no genotypic ratios are provided. Supporting details are therefore only generally complete. (Compare to this Level 3 anchor paper.)


Sample Student Response #4

image of student response

Score for Sample Student Response #4: Rubric Score 2

Annotation: This response demonstrates a basic understanding. Both Punnett squares are correct, and the student's use of "B" instead of "T" is inconsequential. Genotypic and phenotypic ratios are not provided, and the parents' genotypes are not explicitly identified except in the Punnett squares. However, the explanation of the appearance of a long-tailed puppy (one dog in particular got the recesive gene from his parents), is supported by the correct second generation Punnett square, which shows each heterozygous parent contributing a recessive allele to the long-tailed puppy (bb). Overall, supporting details are adequate. (Compare to this Level 2 anchor paper.)


Additional Resources

Anchor Papers used in scoring

Brief Constructed Response (BCR) Rubric
Print: Scoring Rubric (pdf)
Score 4

There is evidence in this response that the student has a full and complete understanding of the question or problem.

  • Pertinent and complete supporting details demonstrate an integration of ideas.
  • The use of accurate scientific terminology enhances the response.
  • An effective application of the concept to a practical problem or real-world situation reveals an insight into scientific principles.*
  • The response reflects a complete synthesis of information.
Score 3

There is evidence in this response that the student has a good understanding of the question or problem.

  • The supporting details are generally complete.
  • The use of accurate scientific terminology strengthens the response.
  • The concept has been applied to a practical problem or real-world situation.*
  • The response reflects some synthesis of information.
Score 2

There is evidence in this response that the student has a basic understanding of the question or problem.

  • The supporting details are adequate.
  • The use of accurate scientific terminology may be present in the response.
  • The application of the concept to a practical problem or real-world situation is inadequate.*
  • The response provides little or no synthesis of information.
Score 1

There is evidence in this response that the student has some understanding of the question or problem.

  • The supporting details are only minimally effective.
  • The use of accurate scientific terminology is not present in the response.
  • The application, if attempted, is irrelevant.*
  • The response addresses the question.
Score 0

There is evidence that the student has no understanding of the question or problem.

  • The response is completely incorrect or irrelevant or there is no response.

* On the High School Assessment, the application of a concept to a practical problem or real-world situation will be scored when it is required in the response and requested in the item stem.

Updated 2002
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