Chapter 12 DNA and RNA Lecture. Order! Genes are made of DNA, a large, complex molecule. DNA is composed of individual units called nucleotides. Three

Chapter 12

DNA and RNA

Lecture

Order! Order!

Genes are made of DNA, a large, complex molecule. DNA is composed of individual units called nucleotides. Three of these units form a code. The order, or sequence, of a code and the type of code determine the meaning of the message.

1. On a sheet of paper, write the word cats. List the letters or units that make up the word cats.

2. Try rearranging the units to form other words. Remember that eachnew word can have only three units. Write each word on your paper, and then add a definition for each word.

3. Did any of the codes you formed have the same meaning?

4. How do you think changing the order of the nucleotides in the DNA codon changes the codon’s message?

Section 12-1 DNA

Objective:

• Summarize the relationship between genes and DNA

• Describe the overall structure of the DNA molecule

Homework section 12-1

Write out all key concepts.

Define each vocabulary word in at least 1 complete sentence.

12–1 DNA

A. Griffith and Transformation

B. Avery and DNA

C. The Hershey-Chase Experiment

D. The Structure of DNA

A. Griffith and Transformation– 1928 Frederick Griffith, British scientist

2. Transformation

Disease-causing bacteria (smooth

colonies)

Harmless bacteria (rough colonies)

Heat-killed, disease-causing bacteria (smooth colonies)

Control(no growth)



Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)

Dies of pneumonia

Figure 12–2 Griffith’s Experiment

Disease-causing bacteria (smooth

colonies)



Control(no growth)



Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)

Dies of pneumonia

Figure 12–2 Griffith’s Experiment

B. Avery and DNA

C. The Hershey-Chase Experiment

1.Bacteriophages

2.Radioactive Markers

Bacteriophage with phosphorus-32 in DNA

Phage infectsbacterium

Radioactivity inside bacterium

Bacteriophage with sulfur-35 in protein coat


No radioactivity inside bacterium

Figure 12–4 Hershey-Chase Experiment















D. The Structure of DNA

1. Chargaff’s Rules

Purines Pyrimidines

Adenine Guanine Cytosine Thymine

Phosphate group Deoxyribose

Figure 12–5 DNA Nucleotides

2. X-Ray Evidence

Percentage of Bases in Four Organisms

Source of DNA A T G CSource of DNA A T G C

Streptococcus 29.8 31.6 20.5 18.0

Yeast 31.3 32.9 18.7 17.1

Herring 27.8 27.5 22.2 22.6

Human 30.9 29.4 19.9 19.8

Streptococcus 29.8 31.6 20.5 18.0

Yeast 31.3 32.9 18.7 17.1

Herring 27.8 27.5 22.2 22.6

Human 30.9 29.4 19.9 19.8

3. The Double Helix

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Figure 12–7 Structure of DNA


Answer all 5 questions on page 294 in at least 3 complete sentences.

Section 12-2 Chromosome and DNA Replication

Objective:• Summarize the events of DNA replication

• Relate the DNA molecule to chromosome structure


• Write out all key concepts.

• Define each vocabulary word in at least one complete sentence.

A Perfect Copy

When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells.

Section 12-2

1. On a sheet of paper, draw a curving or zig-zagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper.

2. Hold the papers side by side, and compare the lines. Do they look the same?

3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same?

4. How could you use the original paper to draw exact copies of the line without tracing it?

5. Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original?

12–2 Chromosomes and DNA Replication

A. DNA and Chromosomes

B. DNA Replication


Chromosome

E. coli bacterium

Bases on the chromosome

Prokaryotic Chromosome Structure

B. DNA Replication


1. DNA Length

2. Chromosome Structure

Figure 12-10 Chromosome Structure of Eukaryotes

Chromosome

Supercoils

Coils

Nucleosome

Histones

DNA

double

helix

B. DNA Replication

1. Duplicating DNA

2. How Replication Occurs

Figure 12–11 DNA Replication

Growth

Growth

Replication fork

DNA polymerase

New strand

Original strand DNA

polymerase

Nitrogenous bases

Replication fork

Original strand

New strand


Answer all questions 299 in at least 3 complete sentences.

Go to Section:

Information, Please

DNA contains the information that a cell needs to carry out all of its functions. In a way, DNA is like the cell’s encyclopedia. Suppose that you go to the library to do research for a science project. You find the information in an encyclopedia. You go to the desk to sign out the book, but the librarian informs you that this book is for reference only and may not be taken out.

1. Why do you think the library holds some books for reference only?

2. If you can’t borrow a book, how can you take home the information in it?

3. All of the parts of a cell are controlled by the information in DNA, yet DNA does not leave the nucleus. How do you think the information in DNA might get from the nucleus to the rest of the cell?

Go to Section:

Section 12-3 RNA and Protein Synthesis

Objective:

• How does RNA differ from DNA

• Name three main types of RNA

• Describe transcription and the editing of RNA

• Identify the genetic code

• Summarize translation

• Explain the relationship between genes and proteinsGo to Section:

Homework 12-3 RNA and Protein Synthesis


Define all vocabulary words in at least one complete sentence.

12–3 RNA and Protein Synthesis

A. The Structure of RNA

B. Types of RNA

C. Transcription

D. RNA Editing

E. The Genetic Code

F. Translation

G. The Roles of RNA and DNA

H. Genes and Proteins

A. The Structure of RNA

B. Types of RNA

C. Transcription

D. RNA Editing

E. The Genetic Code

F. Translation

G.The Roles of RNA and DNA

H.Genes and Proteins

C. Transcription

RNADNA

RNApolymerase

Figure 12–14 Transcription

Section 12-3

Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)

D. RNA Editing

Figure 12–17 The Genetic Code

E. The Genetic Code

F. Translation

Messenger RNA

Messenger RNA is transcribed in the nucleus.

Transfer RNA

The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon.

mRNA Start codon

Ribosome

Methionine

Phenylalanine tRNALysine

Nucleus

Figure 12–18 Translation

mRNA

The Polypeptide “Assembly Line”The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids.

mRNARibosome

Translation direction

Lysine tRNA

tRNA

Ribosome

Growing polypeptide chain

mRNA

Completing the PolypeptideThe process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.

Figure 12–18 Translation (continued)

G.The Roles of RNA and DNA

H.Genes and Proteins

Determining the Sequence of a Gene

DNA contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations.

Section 12-4

1. Copy the following information about Protein X: Methionine—Phenylalanine—Tryptophan—Asparagine—Isoleucine—STOP.

2. Use Figure 12–17 on page 303 in your textbook to determine one possible sequence of RNA to code for this information. Write this code below the description of Protein X. Below this, write the DNA code that would produce this RNA sequence.

3. Now, cause a mutation in the gene sequence that you just determined by deleting the fourth base in the DNA sequence. Write this new sequence.

4. Write the new RNA sequence that would be produced. Below that, write the amino acid sequence that would result from this mutation in your gene. Call this Protein Y.

5. Did this single deletion cause much change in your protein? Explain your answer.

from to to make up

Concept Map

Section 12-3

also called which functions to also called also called which functions towhich functions to

can be

RNA

Messenger RNA Ribosomal RNA Transfer RNA

mRNA Carry instructions rRNACombine

with proteins tRNABring

amino acids toribosome

DNA Ribosome Ribosomes

12–4 Mutations

Objective:

• Contrast gene mutations and chromosomal mutations.

Information, Please

DNA contains the information that a cell needs to carry out all of its functions. In a way, DNA is like the cell’s encyclopedia. Suppose that you go to the library to do research for a science project. You find the information in an encyclopedia. You go to the desk to sign out the book, but the librarian informs you that this book is for reference only and may not be taken out.

1. Why do you think the library holds some books for reference only?

2. If you can’t borrow a book, how can you take home the information in it?

3. All of the parts of a cell are controlled by the information in DNA, yet DNA does not leave the nucleus. How do you think the information in DNA might get from the nucleus to the rest of the cell?

12–4 Homework


Define each vocabulary word in at least one complete sentence.

12–4 Mutations

A. Gene Mutations

B. Chromosomal Mutations

Determining the Sequence of a Gene

DNA contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations.

Substitution InsertionDeletion

Gene Mutations:Substitution, Insertion, and Deletion

Section 12-4

Deletion

Duplication

Inversion

Translocation

Figure 12–20 Chromosomal Mutations

Regulation of Protein Synthesis

Every cell in your body, with the exception of gametes, or sex cells, contains a complete copy of your DNA. Why, then, are some cells nerve cells with dendrites and axons, while others are red blood cells that have lost their nuclei and are packed with hemoglobin? Why are cells so different in structure and function? If the characteristics of a cell depend upon the proteins that are synthesized, what does this tell you about protein synthesis? Work with a partner to discuss and answer the questions that follow.

1. Do you think that cells produce all the proteins for which the DNA (genes) code? Why or why not? How do the proteins made affect the type and function of cells?

2. Consider what you now know about genes and protein synthesis. What might be some ways that a cell has control over the proteins it produces?

3. What type(s) of organic compounds are most likely the ones that help to regulate protein synthesis? Justify your answer.

12–5 Gene Regulation

A. Gene Regulation: An Example

B. Eukaryotic Gene Regulation

C. Regulation and Development

Regulatory sites

Promoter(RNA polymerase binding site)

Start transcription

DNA strand

Stop transcription

Typical Gene Structure

Documents

Chapter 12 DNA and RNA Lecture. Order! Genes are made of DNA, a large, complex molecule. DNA is composed of individual units called nucleotides. Three