1. Be able to draw and label a diagram of the molecular structure of DNA, showing the relationships between the six essential molecules that make up DNA: deoxyribose, phosphate, adenine, cytosine, guanine, thymine.
2. Apply knowledge of complementary base pairing to predict a DNA strand sequence given information about the other DNA strand.
3. Understand the relationship between DNA, nucleotide, gene, and chromosome.
4. Be able to describe and reenact the process of DNA replication, including an explanation of why it produces identical copies of DNA.
5. Distinguish between DNA and RNA.
6. Explain the overall process of protein synthesis (transcription and translation).
7. Apply knowledge of transcription to predict an mRNA sequence given information about a DNA sequence.
8. Apply knowledge of translation to predict a tRNA sequence given information about an mRNA sequence.
9. Apply knowledge of translation to predict an amino acid sequence given information about a tRNA sequence.
10. Distinguish between point/substitution and frameshift/insertion/deletion mutations, and predict their effects on an amino acid sequence.


Deoxyribonucleic acid (DNA)
Nucleic Acid
Base Pair
Double Helix
Protein synthesis
RNA (mRNA and tRNA)
Template strand
Amino acid

Textbook Reference

Chapter 12

Relevant Files

Test Information

100 points. 20 multiple choice questions, 3 points each = 60 points. 5 short answer questions, ranging from 6 to 12 points in value = 40 points total.

Topic breakdown:
DNA and DNA structure: 6 multiple choice = 18 points.
RNA and RNA/DNA compare/contrast: 1 multiple choice + 6 points short answer = 9 points.
Transcription: 4 multiple choice + 4 points short answer = 16 points.
Translation and Protein Synthesis Overall: 7 multiple choice + 24 points short answer = 45 points.
Mutation: 2 multiple choice + 6 points short answer = 12 points.

Sample MCAS Questions

1. Individuals with one form of lactose intolerance do not produce the enzyme lactase because the gene coding for the production of lactase is shut off in their cells. This means that which of the following processes does not occur for the gene?
A. Hydrogenation
B. Mutation
C. Replication
D. Transcription

2. The diagram below shows the final steps of a biochemical pathway used by the bacterium Serratia marcescens to produce a red pigment molecule. Letters X, Y, and Z represent intermediate molecules produced in the pathway. Four enzymes are also involved in the pathway, as shown.
A mutant strain of S. marcescens produces molecules X and Y but does not produce the red pigment molecule or molecule Z. Based on this result, it can be concluded that there must be a mutation in the gene coding for which enzyme?
A. Enzyme 1
B. Enzyme 2
C. Enzyme 3
D. Enzyme 4

3.The diagram below represents part of a process that occurs in cells.
Which process is represented?
A. Meiosis
B. Osmosis
C. Replication
D. Translation

4. Which of the following best describes the result of a mutation in an organism's DNA?
A. The mutation may produce a zygote.
B. The mutation may cause phenotypic change.
C. The mutation causes damage when it occurs.
D. The mutation creates entirely new organisms.

5. The mold Aspergillus flavus grows on grain. A. flavus produces a toxin that binds to DNA in the bodies of animals that eat the grain. The binding of the toxin to DNA blocks transcription, so it directly interferes with the ability of an animal cell to do which of the following?
A. transport glucose across the cell membrane into the cytoplasm
B. produce ATP using energy released from glucose and other nutrients
C. transfer proteins from the endoplasmic reticulum to Golgi complexes
D. send protein-building instructions from the nucleus to the cytoplasm and ribosomes

6. In phenylketonuria (PKU), an enzyme that converts one amino acid into another does not work properly. Which of the following is the most likely cause of this genetic condition?
A. an error in the transcription of the gene for the enzyme
B. a mutation in the DNA sequence that codes for the enzyme
C. an excess of the amino acids necessary to produce the enzyme
D. a structural variation in the amino acid modified by the enzyme

7. Ovalbumin is a protein found in eggs. Which of the following best describes the molecular structure of ovalbumin?
A. a group of six carbon atoms joined in a ring
B. a chain of amino acids folded and twisted into a molecule
C. a set of three fatty acids attached to a molecule of glycerol
D. a sequence of nitrogenous bases attached to a sugar-phosphate backbone

8. Which of the following features of DNA is most important in determining the phenotype of an organism?
A. The direction of the helical twist
B. The number of deoxyribose sugars
C. The sequence of nitrogenous bases
D. The strength of the hydrogen bonds

9. Fireflies produce light inside their bodies. The enzyme luciferase is involved in the reaction that produces the light. Scientists have isolated the luciferase gene. If a scientist inserts the luciferase gene into the DNA of cells from another organism. If these cells produce light, the scientist knows that which of the following occurred?
A. The luciferase gene mutated inside the cells.
B. The luciferase gene was transcribed and translated.
C. The luciferase gene destroyed the original genes of the cells.
D. The luciferase gene moved from the nucleus to the endoplasmic reticulum.

10. 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.

11. In a eukaryotic cell, which of the following processes directly involves DNA?
A. translation
B. cellular respiration
C. active transport of ions
D. replication of chromosomes

(Questions 12-14)
Sickle cell anemia is an autosomal recessive genetic disorder that affects thousands of people in the United States and millions worldwide. Sickle cell anemia commonly occurs in groups whose ancestors came from Africa, as well as South America, Cuba, Central America, Saudi Arabia, India, and the Mediterranean.
Sickle cell anemia is caused by a change in the hemoglobin protein in red blood cells. Sickle cell anemia results in paleness, fatigue, shortness of breath, and increased heart rate due to a deficiency in the oxygen-carrying component of the blood. When oxygen levels are low in an affected individual, the red blood cells become deformed into a curved, sickle shape. People with sickle cell anemia can experience swelling, pain, infection, and organ damage.
All individuals have two alleles for the gene that codes for the hemoglobin protein (Hb). Individuals with two Hb A alleles have normal, round red blood cells. Heterozygous individuals, with one Hb A allele and one Hb S allele, do not experience symptoms of the disease, but they may produce some sickle-shaped red blood cells. Individuals with two Hb S alleles have sickle cell anemia.
The diagrams to the right represent some of the steps in the formation of hemoglobin in two individuals,
Y and Z. In these diagrams, only a small part of the hemoglobin gene sequence is represented.
Individual Y has two Hb A alleles and therefore produces normal red blood cells. Individual Z has two Hb S alleles and therefore produces sickle-shaped red blood cells.
external image 184877_Hemoglobin_series.png

12. Which of the following statements best describes why the change in only one DNA base of the hemoglobin gene results in a different protein product of the gene?
A. The change prevents mRNA from being made.
B. The change alters the amino acid sequence of the protein.
C. The change causes the blood cells to divide in an uncontrolled way.
D. The change creates a second strand of mRNA for each RNA molecule.

13. Which of the following cell structures carries out the process represented by the arrows labeled “2” in the diagrams?
A. mitochondrion
B. nucleus
C. ribosome
D. vacuole

14. Which of the following statements best summarizes a change that is represented by the arrows labeled “3”
in the diagrams?
A. A nucleus is formed in each cell.
B. Each cell divides to form two daughter cells.
C. A chain of amino acids is folded to form a protein in each cell.
D. Proteins are transported through the plasma membrane of each cell.

15. Which of the following statements best describes a DNA molecule?
A. It is a double helix.
B. It contains the sugar ribose.
C. It is composed of amino acids.
D. It contains the nitrogenous base uracil.

16. 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?

17. Which of the following describes DNA replication in eukaryotic cells?
A. A copy of the DNA is made in the nucleus.
B. A molecule of RNA is produced from the DNA.
C. Each strand of DNA is combined with a strand of RNA.
D. Each strand of DNA is separated into a new chromosome.

18. During DNA replication, the wrong nucleotide was inserted in the DNA sequence. Which of the following terms describes this situation?
A. mutation
B. regeneration
C. transcription
D. translation

19. A portion of one strand of a DNA molecule has the sequence shown below.
Assuming there are no mutations in this portion of the DNA, what is the corresponding sequence on the complementary DNA strand?

20. Which of the following units are repeatedly joined together to form a strand of DNA?
A. amino acids
B. fatty acids
C. nucleotides
D. polysaccharides

21. A hereditary muscular disease in horses causes abnormal opening and closing of the sodium ion channels in the muscle cells. Which of the following statements describes the most likely origin of this disease.
A. A virus evolved specifically to attach the muscle cells of the horse.
B. Motor neurons near some of the muscle cells degenerated over time.
C. High levels of sodium in the blood irreversibly damaged the ion channels.
D. A mutation occurred in the gene coding for the sodium ion channel protein.

22. In a molecule of double-stranded DNA, the amount of adenine present is always equal to the amount of
A. cytosine.
B. guanine.
C. thymine.
D. uracil.

23. The diagram below shows a strand of DNA matched to a strand of messenger RNA.
external image 06b910q03.gif
What process does this diagram represent?
A. mutation
B. respiration
C. transcription
D. translation

24. Refer to a genetic code, which maps mRNA codons to amino acids. (note: on the MCAS, you would be provided with a genetic code diagram, it need not be memorized)
Based on the information in the genetic code, which of the following changes is least likely to produce a phenotypic change in an organism?

25. Which of the following statements describes a DNA molecule?
A. It contains the base uracil.
B. It has a double helix shape.
C. It contains five phosphate groups per nucleotide.
D. It has a backbone of twenty different nucleotides.

26. Specific DNA sequences called “promoters” provide binding sites for the enzyme that synthesizes RNA. Promoters are directly involved in which cellular process?
A. Active transport
B. Crossing over
C. Replication
D. Transcription

27. The diagram below shows a pair of DNA nucleotides. The nitrogenous base guanine (G) is labeled.
external image 243374_87655_DNA.png
Which nitrogenous base pairs with guanine?
A. Adenine
B. Uracil
C. Cytosine
D. Thymine

28. The diagram below represents the beginning and end products of a process that occurs in the nucleus of a cell.
external image 211096_VMN_Transcription.png
Which process does the diagram represent?
A. Recombination
B. Replication
C. Translation
D. Transcription

29. A laboratory technique called polymerase chain reaction (PCR) produces millions of copies of a DNA molecule in only a few hours. PCR is most similar to which of the following cellular processes?
A. Mitosis
B. Replication
C. Transcription
D. Translocation

30. Huntington’s disease (HD) is a hereditary disease that destroys brain cells. In individuals with HD, the functioning of a specific protein is altered, and this leads to the disease’s effects. Which of the following is the most likely cause of the altered protein function in individuals with HD?
A. A mutation in the DNA sequence that codes for the protein
B. An increase in the amount of fat rather than protein in the diet
C. A decrease in the amount of glucose and amino acids in the blood
D. A structural abnormality in the endoplasmic reticulum of brain cells

31. Which of the following models most accurately represents the structure of DNA?
A. external image 211256_3254089_AR1_opt_a01.png
B. external image 211256_3254089_AR1_opt_b01.png
C. external image 211256_3254089_AR1_opt_c01.png
D. external image 211256_3254089_AR1_opt_d01.png

32. Which type of cell must contain a mutation in order for the mutation to be passed from a woman to her offspring?
A. Blood cell
B. Egg cell
C. Brain cell
D. Skin cell

33. Which of the following processes produces the nucleotide sequence UUA from the sequence AAT?
A. Meiosis
B. Respiration
C. Replication
D. Transcription

34. Hemoglobin is a protein that carries oxygen in red blood cells. The hemoglobin molecules produced by some people have one specific amino acid that is different from the amino acid at that position in normal hemoglobin. Which of the following is the most likely cause of this amino acid variation?
A. The hemoglobin gene contains a mutation.
B. An error occurs during the folding of the hemoglobin protein.
C. Enzymes replace the amino acid once the hemoglobin is produced.
D. A additional amino acid is mistakenly inserted into the hemoglobin during translation.

1. D
2. C
3. D
4. B
5. D
6. B
7. B
8. C
9. B
11. D
12. B
13. C
14. C
15. A
16. See sample answers here. Those that received a score of 4 were of the highest quality.
17. A
18. A
19. C
20. C
21. D
22. C
23. C
24. D
25. B
26. D
27. C
28. D
29. B
30. A
31. A
32. B
33. D
34. A