MCAS Genetics Open Response Practice Questions
Please provide your answers on a separate piece of lined paper.
Question 1 is an open-response question.
BE SURE TO ANSWER AND LABEL ALL PARTS OF THE QUESTION. Show all your work (diagrams, tables, or computations) in your Student Answer Booklet. If you do the work in your head, explain in writing how you did the work.
Write your answer to question 1 in the space provided in your Student Answer Booklet.
18 A Punnett square is a tool used to predict the outcome of a genetic cross.
a. Make a Punnett square for the cross of a father heterozygous for short fingers and a mother homozygous dominant for short fingers. Use B to indicate the allele for short fingers and b to indicate the allele for long fingers.
b. Identify the expected percentages of the phenotypes in the F1 generation for the cross in part a.
c. Make a Punnett square for the cross of a tall father who is homozygous dominant for height and a short mother who is homozygous recessive for height. Use T to indicate the allele for tall and t to indicate the allele for short.
d. Identify the expected percentages of the phenotypes in the F1 generation for the cross in part c.
Question 2 is an open-response question.
BE SURE TO ANSWER AND LABEL ALL PARTS OF THE QUESTION. Show all your work (diagrams, tables, or computations) in your Student Answer Booklet. If you do the work in your head, explain in writing how you did the work.
Write your answer to question 2 in the space provided in your Student Answer Booklet.
The chart below shows some triplets from a DNA sequence (codons) and their corresponding amino acids.
A sequence of DNA in a gene reads GGT TCG AGA.
a. What is the sequence of amino acids that is produced when this gene is translated?
b. If the DNA is mutated to read GGT TGG AGC, what will the sequence of amino acids be?
c. Rewrite the original DNA sequence with a single mutation that would not change the sequence of amino acids.
d. Explain how a mutation can change the DNA but not change the amino acid sequence.
Write your answer to question 3 in the space provided in your Student Answer Booklet.
In watermelons, solid dark green color (G) is dominant to stripes (g). A student crosses two watermelon plants that are heterozygous for melon color (Gg).
a. In your Student Answer Booklet, make a Punnett square to show this cross. What are the expected percentages of phenotypes of the offspring?
b. The student’s cross produces one hundred watermelon plants. Of those 100 plants, 78 plants produce solid dark green watermelons, and 22 produce striped watermelons. Explain these results based on the Punnett square and predictions you made in part (a).
Question 4 is an open-response question.
• BE SURE TO ANSWER AND LABEL ALL PARTS OF THE QUESTION.
• Show all your work (diagrams, tables, or computations) in your Student Answer Booklet.
• If you do the work in your head, explain in writing how you did the work.
Write your answer to question 4 in the space provided in your Student Answer Booklet.
In 1950, Erwin Chargaff and colleagues examined the chemical composition of DNA and demonstrated that the amount of adenine always equals that of thymine, and the amount of guanine always equals that of cytosine. This observation became known as Chargaff’s rule.
a. Based on current knowledge of the structure of DNA, explain the basis of Chargaff’s rule.
b. The diagram below represents a single-stranded segment of DNA. In your Student Answer Booklet, write the complementary DNA strand that would form from this strand during replication. Use the letters A, C, G, and T to designate the bases: A = adenine; C = cytosine; G = guanine; T = thymine.
c. Why is Chargaff’s rule so important to DNA’s ability to replicate itself accurately?
The following section focuses on inheritance patterns in a pedigree.
Read the information below and use it to answer open-response question that follows.
Earlobes may be free or attached, as shown in the illustrations below. The type of earlobe a person has is genetically determined. The allele for free earlobes (E) is dominant, while the allele for attached earlobes (e) is recessive.
The inheritance of the earlobe trait can be traced over several generations using a family tree called a pedigree. A pedigree for the earlobe trait is shown below.
Question 5 is an open-response question.
BE SURE TO ANSWER AND LABEL ALL PARTS OF THE QUESTION. Show all your work (diagrams, tables, or computations) in your Student Answer Booklet. If you do the work in your head, explain in writing how you did the work.
Write your answer to question 5 in the space provided in your Student Answer Booklet.
On a pedigree, it may not be possible to conclusively determine the genotype of every individual.
a. Can the genotype of male #1 be conclusively determined based on the information given in the pedigree? Explain your answer.
b. Can the genotype of female #2 be conclusively determined based on the information given in the pedigree? Explain your answer.
You may use Punnett squares to support your answers to parts (a) and (b).
Question 6 is an open-response question.
· BE SURE TO ANSWER AND LABEL ALL PARTS OF THE QUESTION
· Show all your work (diagrams, tables or computations) in your Student Answer Booklet.
· If you do the work in your head, explain in writing how you did the work.
Write your answer to question 6 in the space provided in your Student Answer Booklet.
DNA replication and transcription are important processes in cells.
a. Identify the end products of both DNA replication and transcription. Be specific in your answer.
b. Explain the importance of each process in eukaryotic cells.
Write your answer to question 7 in the space provided in your Student Answer Booklet.
People who are tune deaf are unable to follow a rhythm. Scientists have evidence that tune deafness can be genetic. The pedigree below traces the inheritance of tune deafness in a family. Individuals in the pedigree are numbered.
Scientists have analyzed the inheritance patterns for tune deafness and have concluded that tune deafness is caused by an autosomal dominant allele, T.
a. Provide evidence from the pedigree that conclusively shows that the tune deafness allele is autosomal dominant, not autosomal recessive. Explain your reasoning.
b. Identify the genotypes of individuals 5 and 6, and then draw the Punnett square for the cross of these two individuals.
c. Compare the expected percentage of each phenotype of the offspring from the cross in part (b) with the actual percentage of each phenotype observed in the children of individuals 5 and 6.