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From DNA to Proteins

Study Guide B

Answer Key

Section 1. Structure of DNA

NUCLEOTIDE: REFER TO THE VISUAL VOCAB IN SECTION 2 FOR VISUAL ANSWERS. STUDENTS SHOULD LABEL: PHOSPHATE GROUP; NITROGEN-CONTAINING BASE; AND DEOXYRIBOSE SUGAR.

1. 4

2. the phosphate group and the deoxyribose sugar; the nitrogen-containing base

3. that it was of uniform width

4. by building models

5. The sugar-phosphate backbone is on the outside. Inside the structure, a base with two rings always pairs with a base with only one ring.

6. A; G

DNA Double Helix: drawing should include sugar-phosphate backbone; nitrogen-containing bases; and hydrogen bonds

7. The sugar-phosphate backbone is like the twisting handrails of the staircase, and the nitrogen-containing bases are like the steps that connect the railings to each other.

8. Because A only pairs with T and C only pairs with G, the amount of A will be equal to the amount of T, and the amount of C will be equal to the amount of G.

Section 2. DNA Replication

1. THE PROCESS BY WHICH DNA IS COPIED DURING THE CELL CYCLE

2. nucleus

3. S stage

4. so that every cell will have a complete set of DNA following cell division

5. something that serves as a pattern

6. ATCCATG

7. Proteins help unzip the DNA strand, hold the strands apart, and bond nucleotides together.

8. hydrogen bonds connecting base pairs

9. because each molecule consists of one old strand and one new strand

10. Enzymes unzip the helix.

11. DNA polymerase binds nucleotides together to form new strands that are complementary to the original strands.

12. Two identical DNA molecules result.

13. DNA polymerase is an enzyme that makes DNA by forming bonds between nucleotides. The “-ase” ending signals that it is an enzyme. The first part of the word tells that the enzyme makes DNA by stringing together lots of monomers to form polymers.

14. Replication is the process by which DNA is copied during the cell cycle. Accept any reasonable answer. Students may compare replication to making copies on a copier.

15. Share the best bumper stickers with the class.

Study Guide B continued

Section 3. Transcription

1. REPLICATION (NUCLEUS)

2. transcription (nucleus)

3. translation (cytoplasm)

4. Contains the sugar ribose

5. Has the bases A, C, G, and T

6. Typically single-stranded

7. RNA polymerase

8. A large transcription complex, including RNA polymerase and other proteins, assembles at the start of a gene and begins to unwind the DNA. Using one strand of the DNA as a template, RNA polymerase strings together a complementary strand of RNA. The RNA strand detaches from the DNA as it is transcribed, and the DNA zips back together.

9. mRNA: intermediate message that is translated to form a protein; rRNA: forms part of ribosomes; tRNA: brings amino acids from the cytoplasm to a ribosome to help make the growing protein

10. Both occur within the nucleus of eukaryotic cells, are catalyzed by large enzymes, involve unwinding of the DNA double helix, involve complementary base pairing of the DNA strand, and are highly regulated by

the cell.

11. Replication occurs only once during each round of the cell cycle and makes a double-stranded copy of all the DNA in a cell. Transcription occurs repeatedly throughout the cell cycle to make proteins, rRNAs, and tRNAs as needed by a cell. Transcription makes a single-stranded complement of only a particular DNA sequence.

12. mRNA is a form of the DNA message that tells the cell what type of protein to make. rRNA is a key component of ribosomes. tRNA transfers, or carries, amino acids from the cytoplasm to the ribosome.

13. the process of copying a sequence of DNA to produce a complementary strand of RNA

Section 4. Translation

1. THE PROCESS THAT CONVERTS AN MRNA MESSAGE INTO A POLYPEPTIDE, OR PROTEIN

2. sequences of three nucleotides that code for an amino acid

3. RNA

4. the order in which nucleotides are read; they are read as a series of three, nonoverlapping nucleotides

5. arginine (Arg)

6. stop codon

7. UGG

8. glycine (Gly)

9. Ribosomes, tRNA molecules

10. amino acid, anticodon

Cycle Diagram:

A. An exposed codon attracts a complementary tRNA bearing an amino acid.

B. the ribosome forms a peptide bond between the amino acids. It breaks the bond between the first amino acid and tRNA.

C. the ribosome pulls the mRNA strand the length of one codon. The first tRNA exits the ribosome, and another codon is exposed.

11. codons

12. anticodon

13. Stop codons indicate where translation is to stop. (Students may mention that methionine is also a start codon.)

SECTION 5. GENE EXPRESSION AND REGULATION

DIAGRAM LEGEND: EXON; INTRON

1. An exon is a sequence of nucleotides that is expressed in a protein, whereas an intron is an intervening sequence of nucleotides that will be removed during processing.

Section 6. Mutations

1. POINT MUTATION/SUBSTITUTION; FRAMESHIFT MUTATION

2. gene duplication; translocation

3. chromosomal mutation

4. chromosomal mutation

5. the attachment of a piece of one chromosome to a nonhomologous chromosome

6. Answers will vary.

7. Answers will vary.

8. noncoding regions

9. premature stop codon

10. no change

11. lack of regulation

12. altered splice site

13. germ cells/gametes

14. no

15. an agent in the environment that can change DNA

16. UV light can cause neighboring thymine nucleotides to break their hydrogen bonds to adenine and bond with each other instead.

17. a change in an organism’s DNA

18. a frameshift mutation

Section 1: Structure of DNA

Study Guide B

Key Concept

DNA STRUCTURE IS THE SAME IN ALL ORGANISMS.

Vocabulary

|NUCLEOTIDE |BASE PAIRING RULES |

|DOUBLE HELIX | |

MAIN IDEA: DNA IS COMPOSED OF FOUR TYPES OF NUCLEOTIDES.

IN THE SPACE BELOW, DRAW A NUCLEOTIDE AND LABEL ITS THREE PARTS USING WORDS AND ARROWS.

1. How many types of nucleotides are present in DNA?

2. Which parts are the same in all nucleotides? Which part is different?

Study Guide B continued

MAIN IDEA: Watson and Crick developed an accurate model of DNA’s three-dimensional structure.

3. WHAT DID FRANKLIN’S DATA REVEAL ABOUT THE STRUCTURE OF DNA?

4. How did Watson and Crick determine the three-dimensional shape of DNA?

5. How does DNA base pairing result in a molecule that has a uniform width?

MAIN IDEA: Nucleotides always pair in the same way.

6. WHAT NUCLEOTIDE PAIRS WITH T? WITH C?

In the space below, draw a DNA double helix. Label the sugar-phosphate backbone, the nitrogen-containing bases, and the hydrogen bonds.

Vocabulary Check

7. Explain how the DNA double helix is similar to a spiral staircase.

8. How do the base pairing rules relate to Chargaff ’s rules?

Section 2: DNA Replication

Study Guide B

Key Concept

DNA REPLICATION COPIES THE GENETIC INFORMATION OF A CELL.

Vocabulary

|REPLICATION |DNA POLYMERASE |

MAIN IDEA: REPLICATION COPIES THE GENETIC INFORMATION.

1. WHAT IS DNA REPLICATION?

2. Where does DNA replication take place in a eukaryotic cell?

3. When is DNA replicated during the cell cycle?

4. Why does DNA replication need to occur?

5. What is a template?

6. If one strand of DNA had the sequence TAGGTAC, what would be the sequence of the complementary DNA strand?

MAIN IDEA: Proteins carry out the process of replication.

7. WHAT ROLES DO PROTEINS PLAY IN DNA REPLICATION?

8. What must be broken for the DNA strand to separate?

9. Why is DNA replication called semiconservative?

Study Guide B continued

Use words and diagrams to summarize the steps of replication, in order, in the boxes below.

MAIN IDEA: Replication is fast and accurate.

Vocabulary Check

13. Explain what DNA polymerase is by breaking the word into its parts.

14. Write a short analogy to explain what replication is.

Be Creative

15. People sometimes like to display bumper stickers that relate to their trade or field of study. For example, a chemist may have a bumper sticker that says “It takes alkynes to make the world.” Then, chemists or other people who know that an alkyne is a molecule that contains carbon atoms joined by a triple bond get a nice little chuckle out of the play on words. Use your knowledge of DNA replication to write a bumper sticker.

Section 3: Transcription

Study Guide B

Key Concept

TRANSCRIPTION CONVERTS A GENE INTO A SINGLE-STRANDED RNA MOLECULE.

Vocabulary

| |MESSENGER RNA (MRNA) |

|RNA |RIBOSOMAL RNA (RRNA) |

|TRANSCRIPTION |TRANSFER RNA (TRNA) |

|RNA POLYMERASE | |

MAIN IDEA: RNA CARRIES DNA’S INSTRUCTIONS.

LABEL EACH OF THE PROCESSES REPRESENTED BY THE ARROWS IN THE DIAGRAM BELOW. WRITE WHERE EACH OF THESE PROCESSES TAKES PLACE IN A EUKARYOTIC CELL IN PARENTHESES.

Fill in the table below to contrast DNA and RNA.

|DNA |RNA |

|4. Contains the sugar deoxyribose | |

|5. |Has the bases A, C, G, and U |

|6. Typically double-stranded | |

Study Guide B continued

MAIN IDEA: Transcription makes three types of RNA.

7. WHAT ENZYME HELPS A CELL TO MAKE A STRAND OF RNA?

8. Summarize the three key steps of transcription.

9. Write the basic function of each type of RNA in the chart below.

|Type of RNA |Function |

|mRNA | |

|rRNA | |

|tRNA | |

MAIN IDEA: The transcription process is similar to replication.

10. LIST TWO WAYS THAT THE PROCESSES OF TRANSCRIPTION AND REPLICATION ARE SIMILAR.

11. List two ways that the end results of transcription and replication differ.

Vocabulary Check

12. How does the name of each type of RNA tell what it does?

13. What is transcription?

Section 4: Translation

Study Guide B

Key Concept

TRANSLATION CONVERTS AN MRNA MESSAGE INTO A POLYPEPTIDE, OR PROTEIN.

Vocabulary

|TRANSLATION |STOP CODON |ANTICODON |

|CODON |START CODON | |

MAIN IDEA: AMINO ACIDS ARE CODED BY MRNA BASE SEQUENCES.

1. WHAT IS TRANSLATION?

2. What is a codon?

3. Would the codons in Figure 5.1(located in chapter 8 of the textbook) be found in a strand of DNA or RNA?

4. What is a reading frame (look up in textbook)?

Refer to Figure 5.1 (located in chapter 8 of textbook) to complete the table below.

|Codon |Amino Acid or Function |

|5. AGA | |

|6. UAG | |

|7. |tryptophan (Trp) |

|8. GGA | |

MAIN IDEA: Amino acids are linked to become a protein.

9. _______________ AND _______________ ARE THE TOOLS THAT HELP A CELL TRANSLATE AN MRNA MESSAGE INTO A POLYPEPTIDE.

Study Guide B continued

10. A tRNA molecule is attached to an _______________ at one end and has an _______________ at the other end.

Fill in the cycle diagram below to outline the steps of translation.

Vocabulary Check

11. What are AGG, GCA, and GUU examples of?

12. What is a set of three nucleotides on a tRNA molecule that is complementary to an mRNA codon?

13. What do codons code for in addition to amino acids?

Section 5: Gene Expression and Regulation

Study Guide B

Key Concept

GENE EXPRESSION IS CAREFULLY REGULATED IN BOTH PROKARYOTIC AND EUKARYOTIC CELLS.

Vocabulary

| |EXON |

| |INTRON |

THE DIAGRAMS BELOW REPRESENT UNPROCESSED AND PROCESSED MRNA IN A EUKARYOTIC CELL. USING THE DIAGRAMS AS A REFERENCE, FILL IN THE LEGEND WITH THE CORRESPONDING ELEMENT: CAP, EXON, INTRON, TAIL.

Vocabulary Check

1. What is the difference between an exon and an intron?

Section 6: Mutations

Study Guide B

Key Concept

MUTATIONS ARE CHANGES IN DNA THAT MAY OR MAY NOT AFFECT PHENOTYPE.

Vocabulary

|MUTATION |FRAMESHIFT MUTATION |

|POINT MUTATION |MUTAGEN |

MAIN IDEA: SOME MUTATIONS AFFECT A SINGLE GENE, WHILE OTHERS AFFECT AN ENTIRE CHROMOSOME.

1. LIST TWO TYPES OF GENE MUTATIONS.

2. List two types of chromosomal mutations.

3. Which type of mutation affects more genes, a gene mutation or a chromosomal mutation?

4. What leads to gene duplication?

5. What is a translocation?

Below is a string of nucleotides. (1) Use brackets to indicate the reading frame of the nucleotide sequence. (2) Copy the nucleotide sequence into the first box and make a point mutation. Circle the mutation. (3) Copy the nucleotide sequence into the second box and make a frameshift mutation. Use brackets to indicate how the reading frame would be altered by the mutation.

|A G G C G T C C A T G A |

|6. |

|7. |

Study Guide B continued

MAIN IDEA: Mutations may or may not affect phenotype.

FILL IN THE CAUSE-AND-EFFECT DIAGRAM BELOW TO EXPLAIN HOW A POINT MUTATION MAY OR MAY NOT AFFECT PHENOTYPE.

13. For a mutation to be passed to offspring, in what type of cell must it occur?

MAIN IDEA: Mutations can be caused by several factors.

14. CAN DNA POLYMERASE CATCH AND CORRECT EVERY REPLICATION ERROR?

15. What is a mutagen?

16. How does UV light damage the DNA strand?

Vocabulary Check

17. What is a mutation?

18. If a nucleotide is deleted from a strand of DNA, what type of mutation has occurred?

-----------------------

12.

11.

10.

_______________

_______________

_______________

_______________

_______________

_______________

1. _______________

DNA

RNA

Proteins

3. _______________

_______________ ____________

2. _______________

_______________

Ribosome assembles on start codon of mRNA strand.

A.

B.

C.

When the ribosome encounters a stop codon, it falls apart and the protein is released.

Legend

Unprocessed mRNA

Processed mRNA

Don’t Have to Fill In

Don’t Have to Fill In

result in

coding regions

9.

10.

may

occur

in

Point

mutations

11.

result

in

8.

12.

no change

nonfunctional protein

12.

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