Biology - web1.nbed.nb.caweb1.nbed.nb.ca/sites/ASD-W/svhs/science/biol122/Chapter12.pdfBiology . End...

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Copyright Pearson Prentice Hall

Biology

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Vocabulary • DNA

• RNA

• Thymine

• Guanine

• Cytosine

• Hydrogen bond

• Adenine

• Uracil

• Replication

• Protein synthesis

• mRNA

• tRNA

• rRNA

• Transcription

• Translation

• Amino acids

• Ribosome

• Peptide bond

• Watson & Crick

• Chromatin

• histones

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12–1 DNA

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Griffith and Transformation


In 1928, British scientist Fredrick Griffith was

trying to learn how certain types of bacteria

caused pneumonia.

He isolated two different strains of pneumonia

bacteria from mice and grew them in his lab.

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Griffith made two observations:

(1) The disease-causing strain of

bacteria grew into smooth colonies on

culture plates.

(2) The harmless strain grew into

colonies with rough edges.

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Griffith's Experiments

Griffith set up four

individual experiments.

Experiment 1: Mice

were injected with the

disease-causing strain

of bacteria. The mice

developed pneumonia

and died.

../My Documents/Downloads/Resources/Movies/vagriffi.mov

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Experiment 2: Mice

were injected with the

harmless strain of

bacteria. These mice

didn’t get sick.

Harmless bacteria

(rough colonies)

Lives

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Experiment 3: Griffith

heated the disease-

causing bacteria. He

then injected the heat-

killed bacteria into the

mice. The mice

survived.

Heat-killed disease-

causing bacteria (smooth

colonies)

Lives

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Experiment 4: Griffith mixed his heat-killed, disease-causing bacteria with live, harmless bacteria and injected the mixture into the mice. The mice developed pneumonia and died.

Live disease-

causing bacteria

(smooth colonies)

Dies of pneumonia


causing bacteria

(smooth colonies)

Harmless bacteria

(rough colonies)

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Griffith concluded that the heat-killed bacteria passed their disease-causing ability to the harmless strain.

Live disease-

causing bacteria

(smooth colonies)


causing bacteria

(smooth colonies)

Harmless bacteria

(rough colonies)

Dies of pneumonia

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Transformation

Griffith called this process transformation

because one strain of bacteria (the harmless

strain) had changed permanently into another (the

disease-causing strain).

Griffith hypothesized that a factor must contain

information that could change harmless bacteria

into disease-causing ones.

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Avery and DNA

Avery and DNA

Oswald Avery repeated Griffith’s work

to determine which molecule was most

important for transformation.

Avery and his colleagues made an

extract from the heat-killed bacteria that

they treated with enzymes.

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Avery and DNA

The enzymes destroyed proteins,

lipids, carbohydrates, and other

molecules, including the nucleic acid

RNA.

Transformation still occurred.

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Avery and DNA

Avery and other scientists repeated the

experiment using enzymes that would

break down DNA.

When DNA was destroyed,

transformation did not occur. Therefore,

they concluded that DNA was the

transforming factor.

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Avery and DNA

Avery and other scientists discovered

that the nucleic acid DNA stores and

transmits the genetic information from

one generation of an organism to the

next.

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The Hershey-Chase Experiment


Alfred Hershey and Martha Chase studied

viruses—nonliving particles smaller than a cell

that can infect living organisms.

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Bacteriophages

A virus that infects bacteria is known as a

bacteriophage.

Bacteriophages are composed of a DNA or

RNA core and a protein coat.

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They grew viruses in cultures

containing radioactive isotopes of

phosphorus-32 (32P) and sulfur-35 (35S).

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If 35S was found in the bacteria, it would

mean that the viruses’ protein had been

injected into the bacteria.

Bacteriophage with

suffur-35 in protein coat

Phage infects

bacterium No radioactivity

inside bacterium

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If 32P was found in the bacteria, then it was

the DNA that had been injected.

Bacteriophage with

phosphorus-32 in DNA Phage infects

bacterium Radioactivity

inside bacterium

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If 32P was found in the bacteria, then it was

the DNA that had been injected.

Bacteriophage with

phosphorus-32 in DNA Phage infects

bacterium Radioactivity

inside bacterium

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Nearly all the radioactivity in the bacteria was

from phosphorus (32P).

Hershey and Chase concluded that the

genetic material of the bacteriophage was

DNA, not protein.

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12–1 DNA

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The Components and Structure of DNA


DNA is made up of nucleotides.

A nucleotide is a monomer of nucleic acids made

up of:

•Deoxyribose – 5-carbon Sugar

•Phosphate Group

•Nitrogenous Base

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12–1 DNA

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There are four kinds of bases in in DNA:

• adenine

• guanine

• cytosine

• thymine

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12–1 DNA

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Chargaff's Rules

Erwin Chargaff discovered that:

• The percentages of guanine [G] and cytosine

[C] bases are almost equal in any sample of

DNA.

• The percentages of adenine [A] and thymine

[T] bases are almost equal in any sample of

DNA.

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12–1 DNA

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X-Ray Evidence

Rosalind Franklin used X-ray

diffraction to get information

about the structure of DNA.

She aimed an X-ray beam at

concentrated DNA samples

and recorded the scattering

pattern of the X-rays on film.

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12–1 DNA

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The Double Helix

Using clues from Franklin’s pattern, James

Watson and Francis Crick built a model that

explained how DNA carried information and

could be copied.

Watson and Crick's model of DNA was a

double helix, in which two strands were

wound around each other.

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12–1 DNA

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The Components and Structure of

DNA

DNA Double Helix

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12–1 DNA

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The Components and Structure of

DNA

Watson and Crick discovered that hydrogen bonds

can form only between certain base pairs—adenine

and thymine, and guanine and cytosine.

This principle is called base pairing.

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Continue to: Click to Launch:

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12–1

Resources/ch12_sectn01_quiz.qtb

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12–1

Avery and other scientists discovered that

a. DNA is found in a protein coat.

b. DNA stores and transmits genetic

information from one generation to the next.

c. transformation does not affect bacteria.

d. proteins transmit genetic information from

one generation to the next.

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12–1

The Hershey-Chase experiment was based on

the fact that

a. DNA has both sulfur and phosphorus in its

structure.

b. protein has both sulfur and phosphorus in

its structure.

c. both DNA and protein have no phosphorus

or sulfur in their structure.

d. DNA has only phosphorus, while protein

has only sulfur in its structure.

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12–1

DNA is a long molecule made of monomers

called

a. nucleotides.

b. purines.

c. pyrimidines.

d. sugars.

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12–1

Chargaff's rules state that the number of

guanine nucleotides must equal the number of

a. cytosine nucleotides.

b. adenine nucleotides.

c. thymine nucleotides.

d. thymine plus adenine nucleotides.

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12–1

In DNA, the following base pairs occur:

a. A with C, and G with T.

b. A with T, and C with G.

c. A with G, and C with T.

d. A with T, and C with T.

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12-2 Chromosomes and DNA Replication

12–2 Chromosomes and DNA Replication

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Many eukaryotes have 1000 times the

amount of DNA as prokaryotes.

Eukaryotic DNA is located in the cell

nucleus inside chromosomes.

The number of chromosomes varies

widely from one species to the next.

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Chromosome Structure

Eukaryotic chromosomes contain DNA and

protein, tightly packed together to form chromatin.

Chromatin consists of DNA tightly coiled around

proteins called histones.

DNA and histone molecules form nucleosomes.

Nucleosomes pack together, forming a thick fiber.

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Eukaryotic Chromosome Structure

Chromosome

Supercoils

Nucleosome

DNA

double

helix

Histones

Coils

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Duplicating DNA

Before a cell divides, it duplicates its DNA in a

process called replication.

Replication ensures that each resulting cell will

have a complete set of DNA.

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During DNA replication, the DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template for the new strand.

The site of replication is called the replication fork.

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Nitrogen Bases

Replication Fork

DNA Polymerase

Replication Fork

Original strand New Strand

Growth

Growth

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How Replication Occurs

DNA replication is carried out by enzymes that

―unzip‖ a molecule of DNA. This unzipping occurs

when the Hydrogen bonds between base pairs are

broken and the two strands of DNA unwind.

The principle enzyme involved in DNA replication

is DNA polymerase because it joins individual

nucleotides to produce a DNA molecule (polymer).

It also helps to ensure that each molecule is a

perfect copy of the original DNA.

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12–2

In prokaryotic cells, DNA is found in the

a. cytoplasm.

b. nucleus.

c. ribosome.

d. cell membrane.

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12–2

The first step in DNA replication is

a. producing two new strands.

b. separating the strands.

c. producing DNA polymerase.

d. correctly pairing bases.

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12–2

A DNA molecule separates, and the sequence

GCGAATTCG occurs in one strand. What is the

base sequence on the other strand?

a. GCGAATTCG

b. CGCTTAAGC

c. TATCCGGAT

d. GATGGCCAG

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12-3 RNA and Protein Synthesis

12–3 RNA and Protein Synthesis

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Genes are coded DNA instructions that

control the production of proteins.

Genetic messages can be decoded by

copying part of the nucleotide

sequence from DNA into RNA.

RNA contains coded information for

making proteins.

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The Structure of RNA

There are three main differences between RNA and DNA:

a.The sugar in RNA is ribose instead of deoxyribose.

b.RNA is generally single-stranded.

c.RNA contains uracil in place of thymine.

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Types of RNA

There are three main types of RNA:

a.messenger RNA

b.ribosomal RNA

c.transfer RNA

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Messenger RNA (mRNA) carries copies of

instructions for assembling amino acids

into proteins.

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Ribosomes are made up of proteins and

ribosomal RNA (rRNA).

Ribosome

Ribosomal RNA

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During protein construction, transfer RNA

(tRNA) transfers each amino acid to the

ribosome.

Amino acid

Transfer RNA

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DNA

molecule

DNA strand

(template) 3

TRANSCRIPTION

Codon

mRNA

TRANSLATION

Protein

Amino acid

3 5

5

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Transcription (takes place in nucleus)

Promoters: This is a region of DNA that

that indicates to an enzyme where to bind to

make RNA

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RNA

RNA polymerase

DNA

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RNA Editing

• Introns –

sequences of

mRNA NOT

involved in coding

for proteins

• Exons – expressed

sequences of

mRNA


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The Genetic Code

The genetic code is the ―language‖ of mRNA

instructions.

The code is written using four ―letters‖ (the bases:

A, U, C, and G).

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A codon consists of three consecutive

nucleotides on mRNA that specify a

particular amino acid.

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Nucleus

mRNA Copyright Pearson Prentice Hall

Translation

Translation is the decoding of an mRNA

message into a polypeptide chain

(protein).

Translation takes place on ribosomes.

During translation, the cell uses information

from messenger RNA to produce proteins.

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Lysine tRNA Phenylalanine

Methionine

Ribosome

mRNA Start codon

The ribosome binds new tRNA molecules

and amino acids as it moves along the

mRNA.

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Protein Synthesis

tRNA

Ribosome

mRNA

Lysine

Translation direction

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The process continues until the ribosome reaches

a stop codon.

Polypeptide

Ribosome

tRNA

mRNA

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DNA

mRNA

Protein

Codon Codon Codon

Codon Codon Codon

mRNA

Alanine Arginine Leucine

Amino acids within

a polypeptide

Single strand of DNA

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12–3

The role of a master plan in a building is similar

to the role of which molecule?

a. messenger RNA

b. DNA

c. transfer RNA

d. ribosomal RNA

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12–3

A base that is present in RNA but NOT in DNA is

a. thymine.

b. uracil.

c. cytosine.

d. adenine.

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12–3

The nucleic acid responsible for bringing

individual amino acids to the ribosome is

a. transfer RNA.

b. DNA.

c. messenger RNA.

d. ribosomal RNA.

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12–3

A region of a DNA molecule that indicates to an

enzyme where to bind to make RNA is the

a. intron.

b. exon.

c. promoter.

d. codon.

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A codon typically carries sufficient information to

specify a(an)

a. single base pair in RNA.

b. single amino acid.

c. entire protein.

d. single base pair in DNA.


12–3

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12-4 Mutations

12–4 Mutations

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Mutations are changes in the genetic

material.

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Kinds of Mutations

Kinds of Mutations

Mutations that produce changes in a single gene

are known as gene mutations.

Mutations that produce changes in whole

chromosomes are known as chromosomal

mutations.

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Kinds of Mutations

Gene Mutations

Gene mutations involving a change in one or a

few nucleotides are known as point mutations

because they occur at a single point in the DNA

sequence.

Point mutations include substitutions, insertions,

and deletions.

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Kinds of Mutations

Substitutions

usually affect

no more than a

single amino

acid.

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Kinds of Mutations

The effects of insertions or deletions are

more dramatic.

The addition or deletion of a nucleotide

causes a shift in the grouping of codons.

Changes like these are called frameshift

mutations.

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Kinds of Mutations

In an insertion, an

extra base is

inserted into a

base sequence.

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Kinds of Mutations

In a deletion, the loss of a single base is

deleted and the reading frame is shifted.

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Kinds of Mutations

Chromosomal Mutations

Chromosomal mutations involve changes in the

number or structure of chromosomes.

Chromosomal mutations include deletions,

duplications, inversions, and translocations.

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Kinds of Mutations

Deletions involve the loss of all or part of a

chromosome.

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Kinds of Mutations

Duplications produce extra copies of parts of a

chromosome.

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Kinds of Mutations

Inversions reverse the direction of parts of

chromosomes.

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Kinds of Mutations

Translocations occurs when part of one

chromosome breaks off and attaches to another.

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Significance of Mutations

Significance of Mutations

Many mutations have little or no effect on gene

expression.

Some mutations are the cause of genetic

disorders.

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12–4

A mutation in which all or part of a chromosome

is lost is called a(an)

a. duplication.

b. deletion.

c. inversion.

d. point mutation.

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12–4

A mutation that affects every amino acid

following an insertion or deletion is called a(an)

a. frameshift mutation.

b. point mutation.

c. chromosomal mutation.

d. inversion.

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12–4

A mutation in which a segment of a chromosome

is repeated is called a(an)

a. deletion.

b. inversion.

c. duplication.

d. point mutation.

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12–4

The type of point mutation that usually affects

only a single amino acid is called

a. a deletion.

b. a frameshift mutation.

c. an insertion.

d. a substitution.

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12–4

When two different chromosomes exchange

some of their material, the mutation is called

a(an)

a. inversion.

b. deletion.

c. substitution.

d. translocation.

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