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11/28/2012
1
DNA
The
molecule of
heredity 1
• __________ = passing on
of characteristics from parents to offspring
•How? . . . _____
HEREDITY
DNA! 2
DNA
3
I. DNA, Chromosomes, Chromatin and Genes
• ______ = blueprint of life (has the instructions for making
an organism)
• ___________ = uncoiled DNA
• ______________ = coiled DNA
DNA
Chromatin
Chromosome
4
• You have ___ chromosomes or ___ pairs in the ________ of
each body cell.
• _____ from Mom and
_____ from Dad
nucleus
46
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23
23
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• _______ = a segment of DNA that codes for a protein, which in turn codes for a trait (skin tone, eye color, etc); a gene is a stretch of DNA.
–There is a gene for every protein your body has to make.
Gene
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II. DNA
• Deoxyribonucleic Acid
• Located in the
___________________
• Codes for your _______
• _____________
discovered DNA in 1928
nucleus of the cell
genes
Frank Griffith
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A. Shape and Structure
• DNA nucleotide components:
1. _____________
(simple sugar)
2. ___________
_______
3. _______________
(A,T,C,G)
Deoxyribose
Phosphate group
Nitrogen bases
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• Shaped similar to a twisted ladder . . . therefore . . .
____________ !
• The uprights of this
ladder are composed of ____________ and
___________________
double helix
phosphates
deoxyribose sugar
9
B. Base Pairing • 1953:
___________________________________
discovered the DNA double helix.
James Watson and Francis Crick
What you may not
know is that without
___________________ they would have
never made their
discovery.
Rosalind Franklin
10
DNA
• The rungs are
composed of 2
bases (a purine
and pyrimidine)
joined at the
center by weak
__________
bonds.
hydrogen
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DNA
• _________ = adenine (A) and guanine (G)
• _____________ = thymine (T) and cytosine (C)
Purines
Pyrimidines
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Direction of the two DNA strands:
• ___ = orientation of the sugar has carbon on the left
• ___ = orientation of the sugar has carbon on the right
5’
3’
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Direction of the two DNA strands: • The _____ strand is oriented 5’-3’ and
the ________ strand is opposite 3’-5’ top
bottom
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B. Base Pairing • 1962:
___________________________________
discovered that A always bonds with T and C bonds with G
James Watson and Francis Crick
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DNA
• _________ and _________ are complementary. They both
require ___ hydrogen bonds.
• __________ and _________ are
complementary. They both require ___ hydrogen bonds.
Adenine thymine
2
Cytosine guanine
3
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• __________ of bases determines the genetic information and is
unique to each organism.
• If the organisms are closely
related the more _______ the DNA nucleotide sequence
will be.
Sequence
alike
17
• The rungs of the ladder can occur in any order (as long as
the ______________ is followed).
• If the order of base pairs in a
DNA molecule is changed what might occur?
base-pair rule
MUTATIONS!
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• DNA is made of a ________
strand of nucleotides.
• The DNA from each side is
________________ to the other
side.
double
complementary
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• If you know the sequence of one side
you can determine the sequence of
the other side.
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• What is the complementary strand to this DNA molecule?
A A T C G T A C C G A T
T T A G C A T G G C T A
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C. Two Functions of DNA
1. To direct and control
___________________.
2. _________________ = reproducing an exact
copy of DNA so that
the information can
be passed on during
cellular division.
protein synthesis
DNA replication
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D. DNA Replication
____________ is the process where DNA
makes a copy of itself.
Replication
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D. DNA Replication
_____________________________ = parental
strands of DNA separate, serve as a
template, and produce DNA molecules
that have one strand of parental DNA
and one strand of new DNA.
Semiconservative replication
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Semiconservative Replication
• Helps ________ the number copying errors.
• 3 stages: ___________, base pairing, and
joining.
reduce
unwinding
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Why does DNA need to replicate?
• Cells divide for an organism to grow
or reproduce; every new cell needs
a copy of the DNA or instructions to know how to be a cell.
• DNA replicates right
before a cell divides
___________. (MITOSIS)
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E. Replication Steps
1) Unwinding: DNA
helicase (an
_________) unwinds
and unzips the
double helix and
begins to break
the H bonds
between the
nitrogen bases.
enzyme
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E. Replication Steps
2) Base pairing: __________________ (an
enzyme) runs along the parent chain
of DNA in the 3’-5’ direction and bonds
free floating nucleotides to the parent
(original) chain - - based on base
pairing rules.
− The newly assembled strand is called a
________________ of nucleotides and
reforms the double helix.
− Each new strand is a _____________ of
parent strand.
DNA polymerase
leading strand
complement
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E. Replication Steps
3) Because DNA synthesis can only occur
5’ to 3’, a second type of
________________ binds to the other
template strand as the double helix
opens.
− DNA polymerase synthesizes discontinuous
segments of nucleotides (called
___________________).
DNA polymerase
Okazaki fragments
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E. Replication Steps
4) Joining: Another enzyme, _____________
then bonds these Okazaki fragments
together into the ________________.
DNA ligase
lagging strand
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E. Replication Steps
Therefore, the result is the formation of ___
DNA molecules, each of which is identical to
the original DNA molecule.
2
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DNA Replication
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F. What makes up our characteristics?
• If you have brown hair, what makes it
brown, as opposed to blonde, or
red?
• A pigment called
_________,
a _________, is
what you see as
“brown” in the
hair.
melanin
protein
33
What makes you tall or short?
• The lengths of your bones are made
up of a framework of _______________. protein fibers
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So, if heredity material
controls our traits, and your traits are made of
proteins, then shouldn’t heredity material control the making of proteins?
35
• This is exactly what _____ does!!
DNA
nitrogen bases
protein
• The order of
_________________
(A, T, C, G)
determines the
type of _________
that is
assembled.
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• If the order of bases is accidentally
changed, then _______________ occur
which can change the proteins that
need to be made.
mutations
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Radiation and Mutations
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III. Link between DNA & Proteins
• In the cytoplasm of each cell, there
are tiny organelles where proteins are
assembled. What are they called?
39
• If a hair cell needs to
make melanin.
• How do the instructions to synthesize this protein get from the DNA to the ribosome?
40
• Something must carry these instructions from the nucleus to the ribosomes in the cytoplasm. This “messenger” molecule is ________!! mRNA
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A. RNA: Ribonucleic Acid
Structure: DNA RNA
Strands of
nucleotides Double Single
Sugars Deoxyribose Ribose
Nitrogen
bases A, T, C, G A, U, C, G
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• Three kinds of RNA
1. ________
messenger RNA
mRNA
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• Structure: _________________
• Function: Carries the _____
message from the nucleus to
the ribosomes.
• _______ = set of three
nitrogen bases representing an amino acid
single stranded
DNA
Codon
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2. _______ transfer RNA tRNA
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tRNA • Structure: has an ___________ that is a
complement to the ______________ at
one end and an ______________ at the
other end.
anticodon
mRNA codon amino acid
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tRNA • Function: Carries the _____________ to
the ribosomes for protein production.
amino acids
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3. ______ ribosomal RNA
Structure: a part of ribosome
Function: Creates the ___________________ between
the amino acids during
protein production.
rRNA
peptide bonds
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The
molecule of
heredity 49
50
IV. Protein Synthesis
Overview:
• The _________ created is
determined by the base
arrangement in DNA (code sequence)
protein
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_____ transfers this information to mRNA, which carries the code to the ribosome where tRNA decodes it. ______ anticodons base pair with mRNA’s codons. Then ______ forms peptide bonds between ____________ to form a _________.
DNA
tRNA
rRNA amino acids
protein 52
• The process of protein synthesis is broken down into
two sub-processes: transcription and translation.
1. ____________ = the process through which _____ transfers
the code to ______.
Takes place in the _________.
Transcription
DNA
mRNA
nucleus
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2. ____________ = the process through which
mRNA is decoded and forms a protein.
•Takes places at a __________
Translation
ribosome
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Transcription: from DNA to mRNA
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1. _________________ (enzyme)
attaches at a specific
location on DNA.
2. The enzyme then causes
the DNA strands to
separate from one another
and allow one of the DNA
strands to be __________.
RNA polymerase
decoded
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3. mRNA nucleotides are floating around in the nucleus to find their complement on the DNA strand and ______ together. This is possible due to the base-pairing rules.
4. Once the DNA segment has been copied by the mRNA bases, the mRNA strand separates from the DNA.
bond
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5. The mRNA (messenger RNA)
leaves the _________ through
a nuclear pore and enters
the ___________ → goes to
the ___________ for protein
synthesis.
6. DNA zips up again to create
the original double helix.
nucleus
cytoplasm
ribosomes
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Why is Transcription Important?
• It is needed to get the _______________ out of the
_________ so the ribosomes know what _________ to
make!
DNA message
nucleus
protein
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• Without transcription, the ribosome would have no
idea what proteins the body needed and would not
make any.
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You could _____ replace the hair that we lose every day;
could NOT grow long fingernails; be able to fight
off disease; cells would fall apart because the proteins
were not being __________!!
NOT
replaced
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Translation (Protein Synthesis) from RNA to Protein
1. First _______ of mRNA attaches to __________.
codon
ribosome
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2. _______ (transfer RNA) each carries a specific amino acid;
the tRNA anticodon will pair up with its complementary mRNA
codon.
tRNA
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3. When the 1st and 2nd amino acid is
in place, the rRNA joins them by
forming a ________________. As process continues, amino acid chain
is formed until a stop codon.
peptide bond
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4. The tRNA is __________ to find another of the
same amino acid so the process can occur
again and again.
5. The protein chains are
then transported to other areas of the body
that need them.
recycled
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Why is Translation Important?
• Makes all the __________ that the body need.
• Without translation, proteins would not be made and we could not replace the proteins that are depleted or damaged.
proteins
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Summary of Protein Synthesis
• Below you will find the base sequence of a single strand
of DNA. Please fill in the complementary bases of
mRNA, tRNA and the correct amino acid sequence.
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• NOTE: mRNA and tRNA never have ___ in the
sequence! Always use the _______ strand to code for
the ________________.
T’s
mRNA
amino acids
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DNA Code
T A C T T G C A T G G A A T G G T A A C G G T A A C T G
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DNA & mRNA
T A C T T G C A T G G A A T G G T A A C G G T A A C T G
A U G A A C G U A C C U U A C C A U U G C C A U U G A C
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DNA & mRNA & tRNA
T A C T T G C A T G G A A T G G T A A C G G T A A C T G
A U G A AC G U A C C U U A C C A U U GC C A U U GA C
U A C U U B C A U B B A A U B B U A A C B B U A A C U G
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Amino Acids
• Use the mRNA strand!
• AUG – methoinine (start)
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• AAC – asparagine
• GUA – valine
• CCU – proline
• UAC – tyrosine
• CAU – histidine
• UGC – cysteine
• CAU – histidine
• UGA - stop
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Mutations
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MUTATIONS
____________________________ Chromosomal Mutations
Translocation
Inversion Insertion/deletion
Nondisjunction
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MUTATIONS
____________________________ Gene Mutations
Frameshift
Base Insertion Base deletion
Point
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VOCABULARY:
• ____________ = a random error or change in DNA sequence that may affect whole chromosomes or just one gene.
Mutation
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VOCABULARY:
• ____________ = certain substances or conditions that can create a greater rate of mutation
Mutagen
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Mutagens:
• Examples:
–Some _________
–High temperatures
–______________
–Radiation
viruses
Chemicals
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Chromosomal Mutations:
• Changes in chromosomes,
usually during meiosis when
gametes are being made.
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Chromosomal Mutations:
1. ________________ = failure of
homologous chromosomes to
separate during meiosis
resulting in gametes(egg or
sperm) with too few or too many chromosomes.
Nondisjunction
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Chromosomal Mutations:
REMEMBER: Humans are
_________ creatures; meaning
for every chromosome in our
body, there is another one to
match it.
diploid
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Chromosomal Mutation:
____________ =
abnormal number of chromosomes.
Ex. Trisomy,
monosomy
Aneuploidy
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ANEUPLOIDY:
• ________ = zygote contains
three copies of the chromosome.
–Ex: Down
syndrome, Klinefelter’s
(XXY)
Trisomy
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ANEUPLOIDY:
• ____________ = zygote contains
only one chromosome of the pair
(it is missing one chromosome).
Monosomy
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Chromosomal Mutation:
2. _________ = occurs when part
of a chromosome is missing.
Deletion
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Chromosomal Mutation:
3. ______________ = occurs when part
of a chromatid breaks off and attaches to its sister chromatid. The
result is a duplication of genes on the
same chromosome.
Duplication
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Chromosomal Mutation:
4. ___________ = Segment of chromosome
breaks off and is reinserted backwards (will
flip upside down)
Inversion
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Chromosomal Mutation:
5. ________________ = occurs when
part of one chromosome breaks off and is added to a different
chromosome.
Translocation
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Gene Mutations:
Changes in DNA sequence that
will then change the amino
acid sequence. (Remember:
amino acids make up our
proteins!)
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Gene Mutations:
1. ________________ = a change
in a single base pair in DNA.
Point mutation
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Gene Mutations: 2. ______________
_____________ = error in the DNA sequence that adds or deletes a single nitrogen base, causing nearly all amino acids following the mutation to be changed.
Frameshift mutation
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Frameshift Mutation:
• ______________ =
One nitrogen base (A, T, C or G)
is deleted from
the DNA sequence.
Base deletion
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Frameshift Mutation:
• _______________ =
Extra nitrogen
base is added
to the DNA
sequence.
Base insertion
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Mutations
• DNA is constantly subject to mutations, accidental changes in its code.
• Mutations can lead to missing or malformed proteins, and that can lead to disease.
• However, few mutations are bad for you. In fact, some mutations can be beneficial. Over time, genetic mutations create genetic diversity, which keeps populations healthy. Many mutations have no effect at all. These are called silent mutations.
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Mutations: Can be bad but . . .
• Cyclops shark:
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Mutations: Not necessarily a bad thing
• The speckled moth:
Had a mutation that made them black and not speckled. They were easily seen by birds and eaten.
During industrial revolution trees were covered with soot. “Mutated” black moths survived.
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Mutations: Not necessarily a bad thing
• Sickle-Cell Anemia & Malaria:
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Mutations
• The mutations we hear about most often are the ones that cause disease.
• Some well-known inherited genetic disorders include cystic fibrosis, sickle cell anemia, Tay-Sachs disease, phenylketonuria and color-blindness, among many others.
• All of these disorders are caused by the mutation of a single gene.
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