Download •How? . . . _____ - Model High School

11/28/2012
DNA
HEREDITY = passing on
• __________
of characteristics from
parents to offspring
The
molecule of
heredity
DNA!
• How? . . . _____
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DNA
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I. DNA, Chromosomes,
Chromatin and Genes
DNA = blueprint of life (has
• ______
the instructions for making
an organism)
Chromatin = uncoiled DNA
• ___________
Chromosome = coiled DNA
• ______________
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46 chromosomes
• You have ___
23 pairs in the ________
nucleus of
or ___
each body cell.
• _____
23 from Mom and
_____
23 from Dad
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Gene = 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.
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II. DNA
A. Shape and Structure
• Deoxyribonucleic Acid
• Located in the
nucleus of the cell
___________________
genes
• Codes for your _______
Frank Griffith
• _____________
• DNA nucleotide components:
1. _____________
Deoxyribose
(simple sugar)
Phosphate
2. ___________
group
_______
Nitrogen bases
3. _______________
discovered DNA in 1928
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(A,T,C,G)
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B. Base Pairing
• Shaped similar to a twisted
ladder . . . therefore . . .
double
helix !
____________
• The uprights of this
ladder are composed
of ____________
phosphates and
___________________
deoxyribose sugar
• 1953:
James Watson and Francis Crick
___________________________________
discovered the DNA double helix.
What you may not
know is that without
___________________
Rosalind Franklin
they would have
never made their
discovery.
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DNA
DNA
Purines =
• _________
adenine (A) and guanine (G)
Pyrimidines =
• _____________
thymine (T) and cytosine (C)
• The rungs are
composed of 2
bases (a purine
and pyrimidine)
joined at the
center by weak
hydrogen
__________
bonds.
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Direction of the two DNA strands:
5’ = orientation of the sugar
• ___
has carbon on the left
3’ = orientation of the sugar
• ___
has carbon on the right
Direction of the two DNA strands:
• The _____
top strand is oriented 5’-3’ and
bottom
the ________ strand is opposite 3’-5’
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B. Base Pairing
• 1962:
James Watson and Francis Crick
___________________________________
discovered that A always bonds with
T and C bonds with G
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DNA
thymine are
Adenine and _________
• _________
complementary. They both
require ___
2 hydrogen bonds.
• __________
Cytosine and _________
guanine are
complementary. They both
3 hydrogen bonds.
require ___
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Sequence of bases determines
• __________
the genetic information and is
unique to each organism.
• If the organisms are closely
alike the
related the more _______
DNA nucleotide sequence
will be.
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• The rungs of the ladder can
occur in any order (as long as
base-pair rule is followed).
the ______________
• If the order of base pairs in a
DNA molecule is changed
what might occur?
MUTATIONS!
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• DNA is made of
double
a ________
strand of
nucleotides.
• The DNA from
each side is
complementary
________________
to the other
side.
• If you know the sequence of one side
you can determine the sequence of
the other side.
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C. Two Functions of DNA
• What is the complementary
strand to this DNA molecule?
1. To direct and control
protein synthesis
___________________.
DNA replication =
2. _________________
reproducing an exact
copy of DNA so that
the information can
be passed on during
cellular division.
AATCGTACCGAT
T T AG CA T GG C T A
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D. DNA Replication
D. DNA Replication
Semiconservative 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.
____________
Replication is the process where DNA
makes a copy of itself.
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Semiconservative Replication
reduce the number copying errors.
• Helps ________
• 3 stages: ___________,
unwinding base pairing, and
joining.
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
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E. Replication Steps
DNA polymerase (an
2) Base pairing: __________________
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.
1) Unwinding: DNA
helicase (an
enzyme unwinds
_________)
and unzips the
double helix and
begins to break
the H bonds
between the
nitrogen bases.
− The newly assembled strand is called a
leading strand of nucleotides and
________________
reforms the double helix.
− Each new strand is a _____________
complement of
parent strand.
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E. Replication Steps
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E. Replication Steps
DNA ligase
4) Joining: Another enzyme, _____________
then bonds these Okazaki fragments
lagging strand
together into the ________________.
3) Because DNA synthesis can only occur
5’ to 3’, a second type of
DNA polymerasebinds to the other
________________
template strand as the double helix
opens.
− DNA polymerase synthesizes discontinuous
segments of nucleotides (called
___________________).
Okazaki fragments
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E. Replication Steps
DNA Replication
Therefore, the result is the formation of ___
2
DNA molecules, each of which is identical to
the original DNA molecule.
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F. What makes up our characteristics?
What makes you tall or short?
• If you have brown hair, what makes it
brown, as opposed to blonde, or
red?
• A pigment called
melanin
_________,
• The lengths of your bones are made
up of a framework of _______________.
protein fibers
protein is
a _________,
what you see as
“brown” in the
hair.
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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?
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• This is exactly what _____
DNA does!!
• The order of
nitrogen bases
_________________
(A, T, C, G)
determines the
protein
type of _________
that is
assembled.
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• If the order of bases is accidentally
mutations
changed, then _______________
occur
which can change the proteins that
need to be made.
Radiation and Mutations
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• If a hair cell needs to
make melanin.
III. Link between DNA & Proteins
• In the cytoplasm of each cell, there
are tiny organelles where proteins are
assembled. What are they called?
• How do the
instructions to
synthesize
this protein
get from the
DNA to the
ribosome?
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• 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
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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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single stranded
• Structure: _________________
• Function: Carries the _____
DNA
message from the nucleus to
the ribosomes.
• _______
Codon = set of three
nitrogen bases representing
an amino acid
• Three kinds of RNA
mRNA
1. ________
messenger RNA
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tRNA
tRNA transfer RNA
2. _______
anticodon that is a
• Structure: has an ___________
mRNA codon at
complement to the ______________
amino acid at the
one end and an ______________
other end.
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tRNA
amino acids to
• Function: Carries the _____________
the ribosomes for protein production.
rRNA
3. ______
ribosomal RNA
Structure: a part of ribosome
Function: Creates the
peptide bonds
___________________
between
the amino acids during
protein production.
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The
molecule of
heredity
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DNA transfers this
_____
information to mRNA, which
carries the code to the
ribosome where tRNA
tRNA
decodes it. ______
anticodons base pair with
mRNA’s codons. Then
rRNA forms peptide bonds
______
amino acids to
between ____________
form a _________.
protein
IV. Protein Synthesis
Overview:
• The _________
protein created is
determined by the base
arrangement in DNA
(code sequence)
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• The process of protein
synthesis is broken down into
two sub-processes:
transcription and translation.
1. Transcription
____________ = the process
through which _____
DNA transfers
the code to ______.
mRNA
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2. ____________
Translation = the
process through which
mRNA is decoded and
forms a protein.
ribosome
•Takes places at a __________
Takes place in the _________.
nucleus
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Transcription: from DNA to mRNA
1. _________________
RNA polymerase (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
decoded
strands to be __________.
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3. mRNA nucleotides are floating
around in the nucleus to find
their complement on the DNA
strand and ______
bond together. This
is possible due to the basepairing rules.
4. Once the DNA segment has
been copied by the mRNA
bases, the mRNA strand
separates from the DNA.
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5. The mRNA (messenger RNA)
nucleus through
leaves the _________
a nuclear pore and enters
the ___________
cytoplasm → goes to
the ___________
ribosomes for protein
synthesis.
6. DNA zips up again to create
the original double helix.
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• Without transcription, the
ribosome would have no
idea what proteins the body
needed and would not
make any.
Why is Transcription Important?
• It is needed to get the
_______________
DNA message out of the
_________
nucleus so the ribosomes
know what _________
protein to
make!
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Translation (Protein Synthesis)
from RNA to Protein
You could _____
NOT 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 __________!!
replaced
codon of mRNA
1. First _______
attaches to __________.
ribosome
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2. _______
tRNA (transfer RNA) each
carries a specific amino acid;
the tRNA anticodon will pair up
with its complementary mRNA
codon.
4. The tRNA is __________
recycled
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.
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3. When the 1st and 2nd amino acid is
in place, the rRNA joins them by
peptide bond As
forming a ________________.
process continues, amino acid chain
is formed until a stop codon.
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Why is Translation Important?
proteins
• 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.
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Summary of Protein Synthesis
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• NOTE: mRNA and tRNA
never have ___
T’s in the
sequence! Always use the
mRNA strand to code for
_______
amino acids
the ________________.
• 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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DNA Code
DNA & mRNA
TACTTGCATGGAATGGTAACGGTAACTG
TAC TTGCATGGAATGGTAACGGTAACTG
AUGAACGUACCUUACCAUUGCCAUUGAC
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DNA & mRNA & tRNA
Amino Acids
TACTTGCATGGAATGGTAACGGTAACTG
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
• Use the mRNA strand!
• AUG – methoinine (start)
UACUUBCAUBBAAUBBUAACBBUAACUG
• 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
MUTATIONS
Chromosomal Mutations
____________________________
Gene Mutations
____________________________
Translocation
Inversion
Nondisjunction
Point
Frameshift
Base Insertion
Insertion/deletion
Base deletion
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VOCABULARY:
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VOCABULARY:
Mutation =
• ____________
a random error
or change in
DNA sequence
that may affect
whole
chromosomes
or just one
gene.
Mutagen =
• ____________
certain
substances or
conditions
that can
create a
greater rate
of mutation
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Chromosomal Mutations:
Mutagens:
• Changes in
chromosomes,
usually during
meiosis when
gametes are
being made.
• Examples:
–Some viruses
_________
–High temperatures
–______________
Chemicals
–Radiation
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Chromosomal Mutations:
1. ________________
Nondisjunction = failure of
homologous chromosomes to
separate during meiosis
resulting in gametes(egg or
sperm) with too few or too
many chromosomes.
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Chromosomal Mutations:
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Chromosomal Mutation:
REMEMBER: Humans are
diploid creatures; meaning
_________
for every chromosome in our
body, there is another one to
match it.
 ____________
Aneuploidy =
abnormal number
of chromosomes.
Ex. Trisomy,
monosomy
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ANEUPLOIDY:
ANEUPLOIDY:
• ________
Trisomy = zygote contains
three copies of the chromosome.
• ____________
Monosomy = zygote contains
only one chromosome of the pair
(it is missing one chromosome).
–Ex: Down
syndrome,
Klinefelter’s
(XXY)
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Chromosomal Mutation:
Chromosomal Mutation:
2. _________
Deletion = occurs when part
of a chromosome is missing.
3. ______________
Duplication = 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.
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Chromosomal Mutation:
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Chromosomal Mutation:
Inversion = Segment of chromosome
4. ___________
breaks off and is reinserted backwards (will
flip upside down)
5. ________________
Translocation = occurs when
part of one chromosome breaks off
and is added to a different
chromosome.
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Gene Mutations:
Gene Mutations:
Changes in DNA sequence that
will then change the amino
acid sequence. (Remember:
amino acids make up our
proteins!)
1. ________________
Point mutation = a change
in a single base pair in DNA.
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Gene Mutations:
Frameshift Mutation:
2. ______________
Frameshift
_____________
mutation =
error in the DNA
sequence that
adds or deletes a
single nitrogen
base, causing
nearly all amino
acids following
the mutation to
be changed.
• ______________
Base deletion =
One nitrogen
base (A, T, C or G)
is deleted from
the DNA
sequence.
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Frameshift Mutation:
• _______________
Base insertion =
Extra nitrogen
base is added
to the DNA
sequence.
Mutations
Mutations: Can be bad but . . .
• 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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• Cyclops shark:
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Mutations: Not necessarily a bad thing
Mutations: Not necessarily a bad thing
• The speckled moth:
• Sickle-Cell Anemia & Malaria:
During industrial
Had a mutation that
revolution trees weremade them black and
covered with soot. not speckled. They
“Mutated” black
were easily seen by
moths survived.
birds and eaten.
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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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