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Chapter 12
DNA
and
RNA
I. Griffith and Transformation
A. 1928- British scientist Fredrick Griffith learned
how certain types of bacteria caused pneumonia.
B. He isolated two different strains of pneumonia
bacteria from mice and grew them in his lab.
C. Griffith made two observations:
(1) The disease-causing (virulent) strain S-strain of
bacteria grew into smooth colonies on culture plates.
(2) The harmless strain (R-strain) grew into
colonies with rough edges.
D. Griffith's Experiments
1. set up four individual
experiments
a. Experiment 1:
Mice injected with
the disease-causing(virulent) strain of
bacteria, mice got
pneumonia = mice
died.
b. Experiment 2:
Mice injected with
harmless strain of
bacteria = Mice live
c. Experiment 3:
Griffith heated the
disease-causing
bacteria, injected the
heat-killed bacteria
into the mice = mice
lived
d. Experiment 4: heatkilled, disease-causing
bacteria + live,
harmless bacteria and
injected the mixture
into the mice =mice
got pneumonia and
died.
2. Griffith concluded the heat-killed bacteria
passed their diseasecausing ability to the
harmless strain.
3. Transformation
a. Griffith - transformation - one strain of bacteria
(the harmless strain) had changed permanently into
another (the disease-causing strain).
b. Griffith hypothesized that a factor must
contain info. that could change harmless
bacteria into disease-causing ones.
II. Avery and DNA
A. 1944, repeats Griffith’s work
1. 1st stage – destroyed all macromolecules except DNA
a. Transformation still occurred
2. Avery destroyed DNA
a. No transformation occurred
3. Conclusion - transforming factor in bacteria = DNA
III. Hershey-Chase Experiment
A. 1952 – worked with T2 bacteriophages (virus that infects and
kills bacteria) -composed of DNA core with a protein coat
B. Attaches to bacterium and injects its DNA (viral genes)-makes
bacterium a virus factory- “hijacks” cell- produces new T2
bacteriophages and gradually destroys bacterial cell
C. The cell splits open and hundreds of new viruses burst out
D. Hershey-Chase determined it was the DNA that entered and
infected the cell by using radioactive isotopes
p290
IV. Structure of DNA
A. Made up of Nucleotides
1. Sugar (Deoxyribose)
2. Phosphate
3. Nitrogen Base
B. Four nucleotides
1. Adenine  A
2. Guanine  G
3. Thymine  T
4. Cytosine  C
C. Chargaff’s Rules = Base pairing Rules
1. A is found in equal amount to T and
C is found in equal amount to G
2. Therefore, A = T and C = G
D. X-Ray Evidence
1. Rosalind Franklin used X-Ray
diffraction to take a picture of DNA
E. Watson and Crick
1. Used Franklin’s picture of DNA
2. Found out DNA is a double helix (twisted ladder)
DNA Double Helix
Page 294
V. DNA
A. Prokaryotes DNA is located in cytoplasm
1. Single circular DNA- one chromosome with several genes
B. Eukaryotes DNA is located in the nucleus
1. 1,000 X more DNA
2. DNA & protein (histones) = chromatin
a. Form beadlike structure = nucleosome
i. Helps fold long DNA to fit into the tiny space
b. Chromatin tightly coiled up = chromosome
Page 297
VI. DNA Replication (Page 298)
A. DNA molecule produces 2 new complementary strands
B. Starts at a single point (replication fork) and proceeds in two
directions
C. Helicase unwinds and “unzips” DNA
(hydrogen bonds are broken between base pairs)
D. Each strand serves as a template
E. Free floating nucleotides attach to each template
F. DNA polymerase (enzyme) proofreads new strands
G. Each strand contains an old strand and a new strand of DNAcalled SEMI-CONSERVATIVE REPLICATION
Page 298
New Strand
Original strand
Nitrogen Bases
Growth
Growth
Replication Fork
Replication Fork
DNA Polymerase
VII. RNA
A. Single strand of nucleotides (instead of double)
1. Sugar is RIBOSE (instead of deoxyribose in DNA)
2. Base pairing – NO THYMINE:
a. Cytosine = Guanine
b. Adenine = Uracil
B. Types of RNA
1. Messenger RNA (mRNA): Carries instructions for making
proteins from DNA to ribosome
2. Ribosomal RNA (rRNA):
3. Transfer RNA (tRNA):
Makes up ribosomes- helps
assemble proteins
Transfers amino acids to the
ribosome
Page 300
Transcription
Page 301
VIII. GENE EXPRESSION Part I-Transcription (p. 301)
A. mRNA makes a copy of DNA – RNA Polymerase
B. Starts at promoter site on DNA
C. RNA nucleotides pair up with DNA to make mRNA
D. mRNA leaves nucleus: Goes to ribosome
E. TRANSCRIPTION = making mRNA from DNA
Honors Bio Info.
RNA Editing- occurs before leaving nucleus
Poly-A Cap
Guanine Tail
Page 302
IX. RNA Editing-Before leaving nucleus
A. Exon – expressed- sequence of DNA -codes for protein
B. Intron – interrupting noncoding sequences of DNA does not code for protein
C. mRNA strand – introns cut out, so only exons left
D. Final mRNA transcript = exons spliced together; cap and
tail are added (prevents degradation/damage on the way to
ribosome)
Why is this editing important to organisms?
1. One gene on DNA can be cut and spliced to make
different RNA strands for different versions of a protein
2. Role in evolution – very small changes in DNA have
large effects in gene expression (phenotypes)
X. Genetic Code – Triplet Code
A. Three bases read at a time = a one “word” (one amino acid)
B. Codon = sequence of three bases on mRNA that codes for a
specific amino acid
1. Four different letters used to code for 20 amino acids
2. 4 x 4 x 4 = 64 possible codes for 20 amino acids
3. A single amino acid may
have many codons
4. Start codon = AUG = Methionine
(amino acid)
5. Stop codon = UGA, UAA, or UAG
Page 303
Translation
Pages 304 - 305
Lysine
Phenylalanine
Methionine
Ribosome
mRNA
Start codon
tRNA
XI. GENE EXPRESSION Part II- Translation
A. Decoding of mRNA into protein (polypeptide chain)
B. Begins when mRNA attaches to ribosome at start codon
C. Each codon moves through ribosome and correct amino acid is
brought to ribosome by tRNA
1. Anticodon on tRNA pairs with codon on mRNA
2. Anticodon = sequence of three bases on tRNA
D. Peptide bond forms between amino acids
E. mRNA move through until stop codon
F. New protein (polypeptide chain) and mRNA are released
from ribosome
DNA Strand:
T A C A T G
A T G T A C
mRNA Strand:
A U G U A C
(From top DNA strand)
tRNA bases =
anticodon
U A C A U G
Amino Acids =
Methionine - Tyrosine
GENE
EXPRESSION
1. Transcription
2. Translation
XII. Mutations
A. Mutation = change
in genetic material
B. Gene Mutation =
Change in a single gene
1. Point mutation = change in a
single nucleotide
a. Subsitution with no effect =
no a.a change
b. Subsitution with effect =
amino acid change = protein
change
c. Frameshift Mutations
1. Insertion = one
nucleotide is added
2. Deletion = one
nucleotide is taken away
3. Shifts reading frame =
change in amino acids
down the chain
C. Chromosomal Mutations
1. Deletion = loss of part or entire chromosome
2. Duplication = a segment of chromosome is repeated
3. Inversion = part of chromosome becomes reversed
4. Translocation = part of one chromosome breaks off and attaches
to another
D. Polyploidy- having more than 2 sets of chromosomes
1. Beneficial mutation in which entire sets of chromosomes
are duplicated
Ex. Triploid = 3n
Tetraploid = 4n
2. Polyploid plants are larger and stronger (hardier or more
tolerant to adverse conditions) than diploid counterparts
Ex. Bananas, strawberries, and many citrus fruits
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.
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.
12–1
DNA is a long molecule made of monomers
called
A. nucleotides.
B. purines.
C. pyrimidines.
D. sugars.
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.
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.
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.
B.
C.
D.
GCGAATTCG
CGCTTAAGC
TATCCGGAT
GATGGCCAG
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12–2
In addition to carrying out the replication of
DNA, the enzyme DNA polymerase also
functions to
A. unzip the DNA molecule.
B. regulate the time copying occurs in the cell cycle.
C. “proofread” the new copies to minimize the
number of mistakes.
D. wrap the new strands onto histone proteins.
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12–2
The structure that may play a role in regulating
how genes are “read” to make a protein is the
A. coil.
B. histone.
C. nucleosome.
D. chromatin.
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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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12–3
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.
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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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