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Molecular Genetics

Section 1: DNA: The Genetic Material

Section 2: Replication of DNA

Section 3: DNA, RNA, and Protein

Section 4: Gene Regulation and Mutation

DNA: The Genetic Material

Molecular GeneticsSection 1

I. DNA discoveriesA. Griffith Performed the first major experiment that led to

the discovery of DNA as the genetic material

Molecular Genetics

B. Avery

Identified the molecule that transformed the R strain of bacteria into the S strain

Concluded that when the S cells were killed, DNA was released

R bacteria incorporated this DNA into their cells and changed into S cells.


Section 1

Molecular Genetics

C. Hershey and Chase

Used radioactive labeling to trace the DNA and protein

Concluded that the viral DNA was injected into the cell and provided the genetic information needed to produce new viruses


Section 1

Molecular Genetics

II. DNA Structure A. Nucleotides

Consist of a five-carbon sugar, a phosphate group, and a nitrogenous base (Know shapes of the rings!)


Section 1

• Bases will “base pair” with their appropriate match to form double strands. Purines will pair with pyridimines.

• *A pairs with T G pairs with C

Molecular Genetics

B. Chargaff

Chargaff’s rule: C = G and T = A

Each base combination codes for amino acids.


Section 1

• *The “code” is universal because all living organisms share the same code.

• *it is degenerative because more than one set of 3 codes for the same amino acid

Molecular Genetics

C. X-ray Diffraction

X-ray diffraction data helped solve the structure of DNA

Watson and Crick used Rosalind Franklins data along with chargaff’s rules to determine the shape

Indicated that DNA was a double helix


Section 1

Molecular Genetics

Watson and Crick

Built a model of the double helix that conformed to the others’ research

1. two outside strands consist of alternating deoxyribose and phosphate 2. cytosine and guanine bases pair to each other by three hydrogen bonds 3. thymine and adenine bases pair to each other by two hydrogen bonds


Section 1

Molecular Genetics

D. DNA Structure

DNA often is compared to a twisted ladder.

Rails of the ladder are represented by the alternating deoxyribose and phosphate.

The pairs of bases (cytosine–guanine or thymine–adenine) form the steps.


Section 1

Molecular Genetics

Orientation

On the top rail, the strand is said to be oriented 5′ to 3′.

The strand on the bottom runs in the opposite direction and is oriented 3′ to 5′.


Section 1


Molecular Genetics

III. Chromosome Structure

In prokaryotes, DNA in cytoplasm. In eukaryotes: DNA coils around histones to form nucleosomes,

which coil to form chromatin fibers. The chromatin fibers supercoil to form chromosomes

that are visible in the metaphase stage of mitosis.

Section 1

– Come up with a 15 base single strand of DNA for your partner to complete for tomorrows prework.

– Complete p. 332 1-5

1. A2. B3. C4. D

FQ 1

Molecular GeneticsChapter

A. carbohydrate

B. DNA

C. lipid

D. protein

The experiments of Avery, Hershey and Chase provided evidence that the carrier of genetic information is _______.

Section 1 Formative Questions

1. A2. B3. C4. D

FQ 2


A. A—G and C—T

B. A—T and C—G

C. C—A and G—T

D. C—U and A—G

What is the base-pairing rule for purines and pyrimidines in the DNA molecule?


1. A2. B3. C4. D

FQ 3



A.chromatin and histones

B. DNA and protein

C. DNA and lipids

D. protein and centromeres

What are chromosomes composed of?

Replication of DNA

Molecular Genetics

I. Semiconservative Replication

Parental strands of DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA andone strand of new DNA.

Section 2

Molecular Genetics

II. Unwinding (Process and the enzymes)

1. DNA helicase, an enzyme, is responsible for unwinding and unzipping the double helix.

2. RNA primase adds a short segment of RNA, called an RNA primer, on each DNA strand.

Replication of DNA

Section 2

Molecular Genetics

3. DNA polymerase continues adding appropriate nucleotides (in base pairs)to the chain by adding to the 3′ end of the new DNA strand.

Section 2

Molecular Genetics

One strand is called the leading strand and is elongated as the DNA unwinds.

The other strand of DNA, called the lagging strand, elongates away from the replication fork.

The lagging strand is synthesized discontinuously into small segments, called Okazaki fragments.

Replication of DNA

Section 2

Molecular Genetics

Joining

DNA polymerase removes the RNA primer and fills in the place with DNA nucleotides.

4. DNA ligase links the two sections.

Replication of DNA

Section 2

Replication of DNA

Molecular Genetics

III. Comparing DNA Replication in Eukaryotes and Prokaryotes

Eukaryotic DNA unwinds in multiple areas as DNA is replicated.

In prokaryotes, the circular DNA strand is opened at one origin of replication.

Section 2

1. A

2. B

FQ 4


The work of Watson and Crick solved the mystery of how DNA works as a genetic code.

A. TrueB. False


1. A2. B3. C4. D

FQ 5



A. DNA ligase

B. DNA polymerase

C. helicase

D. RNA primer

Which is not an enzyme involved in DNA replication?

DNA, RNA, and Protein

Molecular Genetics

I. Central Dogma (DNA->RNA->protein)

A. RNA

Contains the sugar ribose and the base uracil instead of thymine

Usually is single stranded Sugar=ribose

Section 3

Molecular Genetics

A. Messenger RNA (mRNA) Long strands of RNA nucleotides that are

formed complementary to one strand of DNA

B. Ribosomal RNA (rRNA) Associates with proteins to form ribosomes

in the cytoplasm

C. Transfer RNA (tRNA) Smaller segments of RNA nucleotides that

transport amino acids to the ribosome

II. Types of RNA

Section 3

DNA is unzipped in the nucleus and RNA polymerase binds to a specific section where an mRNA will be synthesized.

Molecular Genetics

III. Transcription (A. The process)

Through transcription, the DNA code is transferred to mRNA in the nucleus.


Section 3

Molecular Genetics

B. RNA Processing (components)

The code on the DNA is interrupted periodically by sequences that are not in the final mRNA.

Intervening sequences are called introns.

Remaining pieces of DNA that serve as the coding sequences are called exons.


Section 3

DNA and Genes

Molecular Genetics

IV. The Code A. Characteristics

1. universal 2. unambiguous (no repeats of codons) 3. degenerate-repeats of amino acids


Section 3

– B. Codons• Groups of 3 bases on the mRNA strand that “code” for

amino acids. These are used in translation (next step)

• C. AUG=start codon– 3 stop codons

Molecular Genetics

V. Translation (mRNA->protein) In translation, tRNA

molecules act as the interpreters of the mRNA codon sequence.

At the middle of the folded strand, there is a three-base coding sequence called the anticodon.

Each anticodon is complementary to a codon on the mRNA.


Section 3

Molecular Genetics


Section 3

• Location: ribosome (out in the cytoplasm)

• A. 5’ end of mRNA connects to ribosome

• B. tRNA brings the aa’s where the anticodon scans the mRNA (anticodon 3’->5’)

• C. Ribosome attach sites

EPA

1.Exit site-used tRNA’s leave

2.P (park) site-place of attachment

3.A site-waiting site

• D. Bonds attach each neighboring aa

• This creates a polypeptide chain (protein)

• E. This continues until a stop codon is reached and then the ribosome subunits disassemble

Molecular Genetics


Section 3


Molecular Genetics

VI. One Gene—One Enzyme

The Beadle and Tatum experiment showed that one gene codes for one enzyme. We now know that one gene codes for one polypeptide.

Section 3

1. A2. B3. C4. D

FQ 6


Which shows the basic chain of events in all organisms for reading and expressing genes?

A. DNA RNA protein

B. RNA DNA protein

C. mRNA rRNA tRNA

D. RNA processing transcription translation


1. A2. B3. C4. D

FQ 7



In the RNA molecule, uracil replaces _______.

A. adenine

B. cytosine

C. purine

D. thymine

1. A2. B3. C4. D

FQ 8



Which diagram shows messenger RNA (mRNA)?

A.

C.

B.

D.

1. A2. B3. C4. D

FQ 9



What characteristic of the mRNA molecule do scientists not yet understand?

A. intervening sequences in the mRNA molecule called introns

B. the original mRNA made in the nucleus called the pre-mRNA

C. how the sequence of bases in the mRNA molecule codes for amino acids

D. the function of many adenine nucleotides at the 5′ end called the poly-A tail

Gene Regulation and Mutation

Molecular Genetics

I. Prokaryote Gene Regulation Ability of an organism to control which genes

are transcribed in response to the environment An operon is a section of DNA that contains

the genes for the proteins needed for a specific metabolic pathway.

Operator Promoter Regulatory gene Genes coding for proteins

Section 4

Molecular Genetics

The Trp Operon


Section 4

Molecular Genetics

The Lac Operon


Section 4

Lac-Trp Operon

Molecular Genetics

II. Eukaryote Gene Regulation

Controlling transcription

Transcription factors ensure that a gene is used at the right time and that proteins are made in the right amounts

The complex structure of eukaryotic DNA also regulates transcription.


Section 4

Molecular Genetics

A. Hox Genes

Hox genes are responsible for the general body pattern of most animals.


Section 4

Molecular Genetics

B. RNA Interference

RNA interference can stop the mRNA from translating its message.


Section 4

Molecular Genetics

III. Mutations

A permanent change that occurs in a cell’s DNA is called a mutation.

Types of mutations Point mutations- 1 base pair change

Substitutions-1 base exchanged for another 1. missense: type of substitution; codes for a

different amino acid! 2. nonsense: changes aa codon to stop!

Terminates translation early; protein functions abnormally!


Section 4

Mutations continued..

• Frameshift mutations: gain or loss of nucleotides (changes the multiples of 3)!! *most disastrous! Changes reading frame!

Types:

1. insertion-addition

2. deletion-loss

*everything will shift at the spot of the mutation because codons are groups of 3!

Mutations cont

• C. Chromosome pieces– Type:

• Tandem repeats: increases the sequences on chromosomes

Molecular Genetics


Section 4

Molecular Genetics

Protein Folding and Stability-can change by mutations

Substitutions also can lead to genetic disorders.

Can change both the folding and stability of the protein


Section 4

Molecular Genetics

Causes of Mutation

Can occur spontaneously DNA polymerase can add wrong

Chemicals and radiation also can damage DNA.

High-energy forms of radiation, such as X rays and gamma rays, are highly mutagenic.


Section 4

Molecular Genetics

Body-cell v. Sex-cell Mutation

Somatic cell (body cells) mutations are not passed on to the next generation.

Mutations that occur in sex cells are passed on to the organism’s offspring and will be present in every cell of the offspring.


Section 4

1. A2. B3. C4. D

FQ 10


Why do eukaryotic cells need a complex control system to regulate the expression of genes?

A. All of an organism’s cells transcribe the same genes.

B. Expression of incorrect genes can lead to mutations.

C. Certain genes are expressed more frequently than others are.

D. Different genes are expressed at different times in an

organism’s lifetime.


1. A2. B3. C4. D

FQ 11



Which type of gene causes cells to become specialized in structure in function?

A. exon

B. Hox gene

C. intron

D. operon

1. A2. B3. C4. D

FQ 12



What is an immediate result of a mutation in a gene?

A. cancer

B. genetic disorder

C. nonfunctional enzyme

D. amino acid deficiency

1. A2. B3. C4. D

FQ 13



Which is the most highly mutagenic?

A. chemicals in food

B. cigarette smoke

C. ultraviolet radiation

D. X rays

Molecular Genetics

Chapter Resource Menu

Chapter Diagnostic Questions

Formative Test Questions

Chapter Assessment Questions

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Vocabulary

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1. A2. B3. C4. D

CDQ 1

A. Watson and Crick

B. Mendel

C. Hershey and Chase

D. Avery

Which scientist(s) definitively proved that DNA transfers genetic material?

Molecular Genetics


Chapter

1. A2. B3. C4. D

CDQ 2

Molecular Genetics


Chapter

A. ligase

B. Okazaki fragments

C. micro RNA

D. helicase

Name the small segments of the lagging DNA strand.

1. A2. B3. C4. D

CDQ 3

Molecular Genetics


Chapter

A. It contains the sugar ribose.

B. It contains the base uracil.

C. It is single-stranded.

D. It contains a phosphate.

Which is not true of RNA?

1. A2. B3. C4. D

CAQ 1


Look at the following figure. Identify the proteins that DNA first coils around.


A. chromatin fibers

B. chromosomes

C. histones

D. nucleosome

1. A2. B3. C4. D

CAQ 2



A. They determine size.

B. They determine body plan.

C. They determine sex.

D. They determine number of body segments.

Explain how Hox genes affect an organism.

1. A2. B3. C4. D

STP 1


What does this diagram show about the replication of DNA in eukaryotic cells?


A. DNA is replicated only at certain places along the chromosome.

B. DNA replication is both semicontinuous and conservative.

C. Multiple areas of replication occur along the chromosome at the same time.

D. The leading DNA strand is synthesized discontinuously.

1. A2. B3. C4. D

STP 2



A. mRNA processing

B. protein synthesis

C. transcription

D. translation

What is this process called?

1. A2. B3. C4. D

STP 3



What type of mutation results in this change in the DNA sequence?

A. deletion

B. frameshift

C. insertion

D. substitution

TTCAGG TTCTGG

1. A2. B3. C4. D

STP 4



How could RNA interference be used to treat diseases such as cancer and diabetes?

A. by activating genes to produce proteins that can overcome the disease

B. by interfering with DNA replication in cells affected by the disease

C. by preventing the translation of mRNA into the genes associated with the disease

D. by shutting down protein synthesis in the cells of diseased tissues

1. A

2. B

STP 5



The structure of a protein can be altered dramatically by the exchange of a single amino acid for another.

A. TrueB. False

Molecular Genetics

Glencoe Biology Transparencies

Chapter

Molecular Genetics

Image Bank

Chapter

Molecular Genetics

Image Bank

Chapter

double helix

nucleosome

Molecular Genetics

Vocabulary

Section 1

Section 1

semiconservative replication

DNA polymerase

Okazaki fragment

Molecular Genetics

Vocabulary

Section 2

Section 2

RNA

messenger RNA

ribosomal RNA

transfer RNA

transcription

RNA polymerase

codon

intron

exon

translation

Molecular Genetics

Vocabulary

Section 3

Section 3

gene regulation

operon

mutation

mutagen

Molecular Genetics

Vocabulary

Section 4

Section 4

Molecular Genetics

Structure of DNA

DNA Polymerase

Transcription

Visualizing Transcription and Translation

Lac-Trp Operon

Animation

Chapter






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