Massachusetts Comprehensive Assessment System

2019, High School Biology

Question 45: Open-Response

Reporting Category: Genetics
Standard: 3.3 - Explain how mutations in the DNA sequence of a gene may or may not result in phenotypic change in an organism. Explain how mutations in gametes may result in phenotypic changes in offspring.
Standard: Sci.HS.LS.1.01 - Construct a model of transcription and translation to explain the roles of DNA and RNA that code for proteins that regulate and carry out essential functions of life. Clarification Statements: Proteins that regulate and carry out essential functions of life include enzymes (which speed up chemical reactions), structural proteins (which provide structure and enable movement), and hormones and receptors (which send and receive signals). The model should show the double-stranded structure of DNA, including genes as part of DNA’s transcribed strand, with complementary bases on the non-transcribed strand. State Assessment Boundaries: Specific names of proteins or specific steps of transcription and translation are not expected in state assessment. Cell structures included in transcription and translation will be limited to nucleus, nuclear membrane, and ribosomes for state assessment.

A certain genetic condition in horses is caused by a single base mutation in a gene. Part of the gene sequence containing the mutation is shown.

TAG AAC CTG AAG

a. Determine the mRNA sequence.

The table shows mRNA codons and their corresponding amino acids.

mRNA	Amino Acid
AUC	Ile
AAG	Lys
CUG	Asp
CUC	Leu
GAC	Asp
UUC	Phe
UUA	Leu
UUG	Leu

b. Determine the amino acid sequence that is coded for by the mRNA sequence you determined in Part A.

The mutated gene codes for Leu instead of Phe.

c. Identify a single base change in the DNA sequence shown that would cause this genetic condition in horses. Explain your answer using amino acids, mRNA codons, and DNA triplets.

Scoring Guide for Idea Development

Select a score point in the table below to view the sample student response.

Score	Description
4	The response demonstrates a thorough understanding of how mutations in the DNA sequence of a gene may or may not result in phenotypic change in an organism. The response correctly determines the mRNA sequence from the DNA sequence and the amino acid sequence that is coded for by the mRNA sequence. The response also correctly identifies a single base change in the DNA sequence that would cause this genetic condition in horses and clearly explains the answer.
4
3	The response demonstrates a general understanding of how mutations in the DNA sequence of a gene may or may not result in phenotypic change in an organism.
2	The response demonstrates a limited understanding of how mutations in the DNA sequence of a gene may or may not result in phenotypic change in an organism.
1	The response demonstrates a minimal understanding of how mutations in the DNA sequence of a gene may or may not result in phenotypic change in an organism.
0	The response is incorrect or contains some correct work that is irrelevant to the skill or concept being measured.

Note: There are 2 sample student responses for Score Point 4.

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Question 44: Evolution and Biodiversity

Question 45: Genetics

Return to the MCAS 2019 Student Work Directory

Last Updated: May 5, 2020