
	Item 38 Anchor Papers

HSA 2006 Biology Item 38

CID: CID822930daf88d0dfe9c1ffd5eba39ff86
itemNum: 38
initialLetter
itemType: BCR
itemAnswerKey: N/A
itemMaxScorePoints: 4
origNum: x

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.

Score Level 1 Anchor Paper
This response demonstrates some understanding of the question. The first-generation Punnett square is correct. The remainder of the response is either a restatement of the prompt (9 out of 10) or incorrect (weak trat; comes out of no were).
Score Level 1 Anchor Paper
This response demonstrates some understanding of the question. The first-generation Punnett square is incorrect, but the second is correct. The student correctly states the probability of a short-tailed puppy in the second generation (75%), but the explanation for having a long-tailed puppy is unclear (heterozygous giving it a 50% chance of having a long tail dog).
Score Level 2 Anchor Paper
This response shows a basic understanding of the question. Both Punnett squares are correct. The student uses adequate details to explain how a long-tailed dog suddenly appeared in the second generation litter (both parents had a long tail gene in them; both parents were heterozygous). The student's discussion of ratios concerns the actual litter (all puppies are short-tailed except one; 1 out of 10) instead of the theoretical probabilities from the Punnett square.
Score Level 2 Anchor Paper
This response demonstrates a basic understanding of the question. Both Punnett squares are correct and the genotypes of the parents are identified (TT & Tt). The genotypic and phenotypic ratios are not provided, however adequate support is given for the explanation of how a long-tailed puppy could appear (both of his/her parents were most likely Heterzygous).
Score Level 2 Anchor Paper
This response demonstrates a basic understanding of the question. The parents' genotypes for both generations (TT, Tt; Tt, Tt) are identified, and both Punnett squares are correct. The explanation of how a long-tailed puppy could have two short-tailed parents is brief but accurate (only when both parents are heterozygous (allels are Tt, Tt)). Supporting details, found mostly in the correct Punnett square for the second generation, are adequate, although the student lists the actual ratios of puppies in the litters (12:0; 9:1) instead of the correct phenotypic ratios determined from the Punnett square, and the genotypic ratios are omitted altogether.
Score Level 3 Anchor Paper
This response shows a good understanding of the question. The student provides generally complete details to explain each part of the question. The student identifies the genotype of the parents (1^st parent was homozygous dominant…TT; the second parent was heterozygous….Tt) and correctly completes both Punnett squares. The genotypic and phenotypic ratios are reversed and not labeled (In the first generation the genotypic ratio was 4. The phenotypic was 2-2). The student explains how a long-tailed puppy could appear (both parents were carriers of the recessive gene for long tails) and additionally supports this statement by circling the genotype in the Punnett square. Overall the supporting details are generally complete.
Score Level 3 Anchor Paper
This response demonstrates a good understanding of the question. The genotypes of the parents are not explicitly identified, but the correct Punnett squares make it clear that the student knows what they are. Genotypic ratios (1:1; 1:2:1) are correct numerically though unlabeled. The phenotypic ratio for the first generation is incorrect (1:1), but that for the second is numerically accurate (3:1). Despite some incorrect use of terminology (homozygous long tailed offspring), which combines the genotype and phenotype, supporting details for the conclusion, including the Punnett square (both parents are heterozygous; pass down a little t), are generally complete.
Score Level 4 Anchor Paper
This response demonstrates a full and complete understanding of the question. Phenotypic ratios are fully specified for both generations (4 short-tail: 0 long-tail; 3 short-tail: 1 long-tail), as are the genotypic ratios (2 TT: 2 Tt: 0 tt; 1 TT: 2 Tt: 1 tt). The Punnett squares are correct. The conclusion includes all pertinent details (a puppy recieved a recessive allele from both parents), and scientific terminology (carried but did not express) enhances the response. The markings on the Punnett squares help to integrate all aspects of the response (one taken from the 1^st generation litter).
Score Level 4 Anchor Paper
This response shows a full and complete understanding. Both Punnett squares are correct. The genotypic ratios are correct and fully labeled (25% homozygous dominant, 25% homozygous recessive and 50% heterozygous), demonstrating both inclusion of all pertinent details and the accurate use of scientific terminology. Elsewhere, terminology also enhances the response (carry the gene). The student integrates all aspects of the question with strong supporting details and synthesis (must have both carried the recessive trait; Because short tails are a dominant trait, a heterozygous dog will have a short tail), fully explaining the appearance of a long-tailed puppy (because the two recessive genes merged together).

Anchor Papers ~ Biology ~ Item 38

HSA 2006 Biology Item 38

CID: CID822930daf88d0dfe9c1ffd5eba39ff86
itemNum: 38
initialLetter
itemType: BCR
itemAnswerKey: N/A
itemMaxScorePoints: 4
origNum: x

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.

Score Level 1 Anchor Paper
This response demonstrates some understanding of the question. The first-generation Punnett square is correct. The remainder of the response is either a restatement of the prompt (9 out of 10) or incorrect (weak trat; comes out of no were).

Score Level 1 Anchor Paper
This response demonstrates some understanding of the question. The first-generation Punnett square is incorrect, but the second is correct. The student correctly states the probability of a short-tailed puppy in the second generation (75%), but the explanation for having a long-tailed puppy is unclear (heterozygous giving it a 50% chance of having a long tail dog).

Score Level 2 Anchor Paper

This response shows a basic understanding of the question. Both Punnett squares are correct. The student uses adequate details to explain how a long-tailed dog suddenly appeared in the second generation litter (both parents had a long tail gene in them; both parents were heterozygous). The student's discussion of ratios concerns the actual litter (all puppies are short-tailed except one; 1 out of 10) instead of the theoretical probabilities from the Punnett square.

Score Level 2 Anchor Paper
This response demonstrates a basic understanding of the question. Both Punnett squares are correct and the genotypes of the parents are identified (TT & Tt). The genotypic and phenotypic ratios are not provided, however adequate support is given for the explanation of how a long-tailed puppy could appear (both of his/her parents were most likely Heterzygous).

Score Level 2 Anchor Paper

This response demonstrates a basic understanding of the question. The parents' genotypes for both generations (TT, Tt; Tt, Tt) are identified, and both Punnett squares are correct. The explanation of how a long-tailed puppy could have two short-tailed parents is brief but accurate (only when both parents are heterozygous (allels are Tt, Tt)). Supporting details, found mostly in the correct Punnett square for the second generation, are adequate, although the student lists the actual ratios of puppies in the litters (12:0; 9:1) instead of the correct phenotypic ratios determined from the Punnett square, and the genotypic ratios are omitted altogether.

Score Level 3 Anchor Paper

This response shows a good understanding of the question. The student provides generally complete details to explain each part of the question. The student identifies the genotype of the parents (1^st parent was homozygous dominant…TT; the second parent was heterozygous….Tt) and correctly completes both Punnett squares. The genotypic and phenotypic ratios are reversed and not labeled (In the first generation the genotypic ratio was 4. The phenotypic was 2-2). The student explains how a long-tailed puppy could appear (both parents were carriers of the recessive gene for long tails) and additionally supports this statement by circling the genotype in the Punnett square. Overall the supporting details are generally complete.

Score Level 3 Anchor Paper

This response demonstrates a good understanding of the question. The genotypes of the parents are not explicitly identified, but the correct Punnett squares make it clear that the student knows what they are. Genotypic ratios (1:1; 1:2:1) are correct numerically though unlabeled. The phenotypic ratio for the first generation is incorrect (1:1), but that for the second is numerically accurate (3:1). Despite some incorrect use of terminology (homozygous long tailed offspring), which combines the genotype and phenotype, supporting details for the conclusion, including the Punnett square (both parents are heterozygous; pass down a little t), are generally complete.

Score Level 4 Anchor Paper

This response demonstrates a full and complete understanding of the question. Phenotypic ratios are fully specified for both generations (4 short-tail: 0 long-tail; 3 short-tail: 1 long-tail), as are the genotypic ratios (2 TT: 2 Tt: 0 tt; 1 TT: 2 Tt: 1 tt). The Punnett squares are correct. The conclusion includes all pertinent details (a puppy recieved a recessive allele from both parents), and scientific terminology (carried but did not express) enhances the response. The markings on the Punnett squares help to integrate all aspects of the response (one taken from the 1^st generation litter).

Score Level 4 Anchor Paper

This response shows a full and complete understanding. Both Punnett squares are correct. The genotypic ratios are correct and fully labeled (25% homozygous dominant, 25% homozygous recessive and 50% heterozygous), demonstrating both inclusion of all pertinent details and the accurate use of scientific terminology. Elsewhere, terminology also enhances the response (carry the gene). The student integrates all aspects of the question with strong supporting details and synthesis (must have both carried the recessive trait; Because short tails are a dominant trait, a heterozygous dog will have a short tail), fully explaining the appearance of a long-tailed puppy (because the two recessive genes merged together).