Download Chemistry In Your Life

Chapter 9
Nucleic Acids and Proteins
The Molecules That Make You What
You Are
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Chemistry Applied
•DNA and RNA: carrying genetic
information
•RNA: translating genetic
information
•Proteins
•Human Genetics
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Nucleic Acids: DNA and RNA Structures
and Properties
1. The basic units of DNA and RNA are
nucleotides.
• DNA and RNA are
large polymer
molecules called
nucleic acids.
• The subunits in DNA
and RNA are called
nucleotides.
• A nucleotide is made
up of an acidic
phoshate unit, a
sugar, and a nitrogen
base.
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Nucleic Acids: DNA and RNA Structures
and Properties
• DNA and RNA differ
in the type of sugar
and in one type of
nitrogen base.
• DNA contains the
sugar deoxyribose
while RNA contains
the sugar ribose.
• Each sugar is
condensed with a
nitrogenase base to
form a nucleoside.
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Nucleic Acids: DNA and RNA Structures
and Properties
• Three different
nitrogenous bases occur
in both DNA and RNA.
The fourth possible base
is different in DNA and
RNA.
• The sequences of bases
do not form any regular
repeating pattern. Their
sequence represents a
code from which all
information about the
living system can be
obtained.
• The five bases are:
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Nucleic Acids: DNA and RNA Structures
and Properties
• Guanine and adenine are classified as purines. Cytosine,
thymine, and uracil are classified as pyrimidines.
• The bases are assigned the codes:
•A
adenine
•C
cytosine
•G
guanine
•T
thymine
•U
uracil
• A, G, and C are found in both DNA and RNA.
• T is found only in DNA and U is found only in RNA.
• DNA stands for the chemical name: deoxyribonucleic
acid, while RNA stands for the chemical name: ribonucleic
acid.
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Nucleic Acids: DNA and RNA Structures
and Properties
2. Nucleotides are joined together to
form biological polymers.
• Individual nucleotides are connected in DNA and RNA
through condensation reactions:
+ 2 H 2O
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Nucleic Acids: DNA and RNA Structures
and Properties
• A short section of DNA:
Copyright W. H. Freeman and Company ·
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Nucleic Acids: DNA and RNA Structures
and Properties
3. DNA is a double helix.
• Based on the work of
James Watson, Francis
Crick, and Rosalind
Franklin in the 1950’s, we
now know DNA is a double
helix of two separate DNA
chains running in opposite
directions.
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Nucleic Acids: DNA and RNA Structures
and Properties
• Hydrogen bonding
between the bases, which
form base pairs stacked
on top of each other at the
center of the helix, holds
the chains together.
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Nucleic Acids: DNA and RNA Structures
and Properties
• In the double helix, an
A base on one strand
is always hydrogen
bonded to a T base on
the other strand and
vise-versa. The same
is true for a G base
and a C base. This is
called the principle of
complementarity.
• The principle of
complementarity is
basis for replication,
the process where a
copy of the DNA
double helix is made.
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Nucleic Acids: DNA and RNA Structures
and Properties
• In replication, the DNA double helix unwinds and each
strand provides a template along which complementary
bases align and are polymerized.
• Replication is fast and almost always accurate. Occasional
inaccuracies, when the occur, represent mutations.
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DNA: The Genetic Message
4. The structure of DNA carries information
as a linear sequence of nucleotides.
• The language in DNA is carried by the sequence of four
bases: A, C, T, and G. Words of three letters represent
the basic vocabulary in DNA.
• There are 64 possible “words” contained in the 3 letter
DNA genetic code.
• Most of these words specify the identity of one of twenty
amino acids contained in protein molecules.
• A few words specify the position in the “text” where the
code for a particular protein starts and stops.
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DNA: The Genetic Message
5. Specific sequences of nucleotides are
genes.
• Long strands of DNA are stored within the nucleus of most
cells in the form of chromosomes.
• The number of chromosomes varies with species (Human =
26 or 23 pairs)
• The DNA within a chromosome is divided into many
segments, many of which carry specific information in the
form of genes.
• Genes are separated from each other by intergenic regions.
• Each gene is preceded by a regulatory region in the DNA
which allows the gene to be turned on and off.
• When a gene is turned on, its information is transferred to
RNA which is then “translated” into specific proteins.
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DNA: The Genetic Message
6. The Human Genome Project
• Since 1990, researchers have been determining the DNA
sequence of the entire human genome.
• They have produced a working draft which identifies
individual gene sequences and maps their locations on the
23 pairs of human chromosomes.
• More than 30,000 gene have been identified.
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RNA: The Genetic Message Translator
7. Genetic information goes from DNA
to RNA to protein.
• Genetic information in the form of DNA is contained in
the nucleus of most cells. The site of protein synthesis is
outside the nucleus in the cytoplasm of the cell, however.
• DNA cannot leave the nucleus, so a copy of the relevant
segment of the DNA called mRNA is made and exported
to the cytoplasm. The synthesis of this mRNA is called
transcription.
• The mRNA provides the instructions for ribosomes in the
along with transfer RNA’s (tRNA) in the cytoplasm to
construct the protein.
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RNA: The Genetic Message Translator
8. Information on DNA is transferred by
transcription of a complementary
sequence of nucleotides on mRNA.
• To build a complementary mRNA sequence from DNA, the
DNA must first unwind to expose the bases.
• A protein enzyme called RNA polymerase assists in
bringing unattached nucleotide bases and correctly paring
them to the exposed DNA bases. The RNA polymerase
then catalyzes the polymerization of the assembled
nucleotides.
• The RNA produced is a complementary copy of the
segment of DNA transcribed.
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RNA: The Genetic Message Translator
Copyright W. H. Freeman and Company ·
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RNA: The Genetic Message Translator
9. RNA codons dictate the sequence of
amino acids in a protein.
• A sequence
of three
successive
nucleotides
on a mRNA
molecule is
called a
codon.
• The
correlation
of codons to
amino acids
is:
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RNA: The Genetic Message Translator
• Note that for most
amino acids there is
more than one
codon assigned.
• In addition, several
codons specify start
and stop signals
specifying the
beginning and end
of the corresponding
protein.
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RNA: The Genetic Message Translator
10. Ribosomes build polypeptides.
• Translation is the process of converting the three letter
codes specified in the mRNA to the 20 amino acid
alphabet of proteins.
• This process is carried out by large structures called
ribosomes which are built from several segments of rRNA
and a group of ribosomal proteins.
• Ribosomes contain sites where mRNA and two tRNA’s can
bind.
• There is at least one tRNA for each of the 20 amino acids.
Each tRNA contains three bases in its sequence called the
anticodon, which is complementary to the codon for the
amino acid in question.
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RNA: The Genetic Message Translator
• At the other end of the tRNA is a site where the amino
acid itself is attached by an enzyme. The amino acid
corresponding to the anticodon of the tRNA is always
attached correctly.
• As the ribosome reads the codons on the mRNA, it assembles
tRNAs with matching anticodons in the correct sequence and
polymerizes the amino acids they carry.
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RNA: The Genetic Message Translator
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RNA: The Genetic Message Translator
11. Cells regulate gene activity by turning
genes on and off.
• The production of functioning proteins is call gene
expression.
• The genes that are functioning at a given time depend
upon the type of cell (liver, heart, skin, etc.), the
developmental stage of the cell, and sometimes upon
varying conditions outside the cell.
• Proteins and other molecules carry out the gene regulation
process.
• Housekeeping gene are “on” all the time and manage the
basic functions of the cell
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RNA: The Genetic Message Translator
• When genes need to be turned on, activator proteins which
recognize and bind to specific DNA sequences are often
involved.
• Once bound, they help the RNA polymerase bind to the
DNA.
• Repressor proteins bind to DNA sequences and prevent
RNA polymerase from binding, thus shutting off the gene.
• The signals to activator and repressor proteins that cause
them to bind or not bind to the DNA are often small signal
molecules. These molecules bind to the proteins and
change their shape.
• The signal molecules can be anything from nutrients
(glucose, lactose, maltose) to carcinogens, to drugs.
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RNA: The Genetic Message Translator
1. Information from genes on
DNA is transcribed to an
mRNA.
2. mRNA leaves the nucleus
through nuclear pores.
3. mRNA binds to a site on a
ribosome.
4. mRNA and the first tRNA
molecules are brought together
within the ribosome, initiating
construction of a polypeptide.
5. mRNA moves through the
ribosome. As each codon is
“read”, a new amino acid is
added to the growing
polypeptide chain.
6. A stop signal on the mRNA is
encountered and the peptide
chain is released.
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The Genetic Message Expressed I: Protein
Form
12. Proteins are polyamides.
• Proteins are non-branched condensation polymers of alpha
amino acids.
• Shorter proteins are often called polypeptides.
• There are twenty different alpha amino acids in human
proteins, formed by varying the –R group above.
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The Genetic Message Expressed I: Protein
Form
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The Genetic Message Expressed I:
Protein Form
13. Polypeptides are relatively short
chains of amino acids.
• Two amino acids are joined in a polypeptide or protein by
a peptide bond.
• Greek prefixes designate the number of amino acids for
the first few numbers and then the term polypeptide is
used (for instance, dipeptide, tripeptide, etc.)
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The Genetic Message Expressed I:
Protein Form
• The artificial sweetener, aspartame, is the di-peptide:
Asp-Phe.
• Note that this is a different chemical substance than
Phe-Asp.
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The Genetic Message Expressed I:
Protein Form
• Because some people with an inborn condition called
phenylketonuria (PKU) cannot metabolize phenylalanine,
those people must avoid using aspartame as a sweetener
and avoid foods cooked using aspartame.
• Endorphins are naturally occurring polypeptides in the body
in the chemical group called opioids. These molecules
naturally relieve pain and produce pleasant sensation.
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The Genetic Message Expressed I:
Protein Form
14. Protein shapes are determined by
interactions of backbones and side
chains.
• Proteins fold up to have specific shapes containing regions
that interact in a very specific way with various smaller
molecules, and sometimes other protein molecules.
• Protein structure is viewed at four levels of complexity:
•Primary structure
•Secondary structure
•Tertiary structure
•Quaternary structure
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The Genetic Message Expressed I:
Protein Form
• Primary structure is simply the sequence of amino acids
making up the polypeptide chain.
• The R groups of amino acids can be classified as polar,
non-polar. The polar amino acids are hydrophylic (water
loving) and the non-polar amino acids are hydrophobic
(water hating).
• The completed protein chain will fold up in such a way to
place the hydrophobic side chains at the center of the
protein, away from contact with the solvent, and the
hydrophylic side chains at the surface, where they can
interact with the solvent.
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The Genetic Message Expressed I:
Protein Form
• Secondary structure is ordered hydrogen bonding between
one part of the polypeptide chain to another part. Two of
the most important patterns of secondary structure are the
alpha helix and the beta pleated sheet.
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The Genetic Message Expressed I:
Protein Form
• In the alpha helix, the N-H unit of each amino acid hydrogen
bonds with the C=O in the fourth amino acid further along in
the sequence.
• The R groups all protrude outward from the alpha helix and
the center is hollow.
• The alpha helix predominates in alpha keratins (hair, skin,
nails)
• In the beta pleated sheet, the polypeptide chain zigs back
and forth within a plane. Hydrogen bonds between N-H and
C=O groups on adjacent strands hold the peptide in a more
or less planar structure.
• The beta pleated sheet predominates in silk.
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The Genetic Message Expressed I:
Protein Form
• Tertiary structure is the
overall folding of a protein,
including its secondary
structure into a globular three
dimensional shape.
• The folding is determined by:
•Salt bridge attractions
between –COO- and –NH3+
groups
•Hydrogen bonds
•Covalent S-S (disulfide)
bonds
•Weak attractions between
hydrophobic groups
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The Genetic Message Expressed I:
Protein Form
• Quaternary structure is the arrangement of subunits within a
protein which consists of more than one separate polypeptide
chain.
• An well studied example of a protein having a quaternary
structure is hemoglobin.
• This protein is found in red blood cells and is responsible for
carrying oxygen from the lungs to the tissues.
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The Genetic Message Expressed I:
Protein Form
15. Your hair curls or doesn’t curl due to
disulfide bridges and hydrogen bonds.
• In human hair, two alpha helical proteins coil around each
other, forming a supercoil. The supercoil structure is locked
in place by –S-S- bonds between adjacent proteins.
• Whether your hair is straight or curly, the shape is locked
into place by these –S-S- bonds.
• In permanent waving or straightening of hair, a chemical
treatment breaks the –S-S- bonds and the hair is placed in
the desired shape.
• A second chemical is then applied which remakes the –S-Sbonds, this time locking the hair into the new desired
shape.
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The Genetic Message Expressed I:
Protein Form
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The Genetic Message Expressed II:
Protein Function
16. You need protein in your diet.
• The human body requires about a gram of protein per
kilogram of body weight per day. This protein is digested
to provide a pool of alpha amino acid needed for human
protein synthesis.
• Digestive enzymes speed up the reverse polymerization of
proteins by catalyzing the addition of water to the amide
bonds holding the amino acids together.
• Sources of protein include fish, meat, and beans.
• Out of the 20 amino acids needed, 10 are essential amino
acids. The human body cannot synthesize these amino
acids or produce them by rearranging amino acids of
another type contained in your diet.
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The Genetic Message Expressed II:
Protein Function
17. What is a complete protein?
• A dietary protein is a complete protein if it contains all of
the essential amino acids in the correct proportions required
for human proteins.
• Examples of complete proteins are meat, seafood, poultry,
milk, human milk, cheese, and eggs.
• Examples of incomplete proteins include wheat, corn, rice
and oats, all low in lysine and some in tryptophan, both
essential amino acids.
• Legumes, such as beans and peas are high in lysine and
tryptophan but low in other essential amino acids.
• Combining grains and legumes at a meal does provide
adequate amounts of all of the essential amino acids.
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The Genetic Message Expressed II:
Protein Function
• If only one essential amino acid is missing from the diet,
creation of dependant proteins will cease to some extent.
• Dietary protein transformation into human protein can be
summarized:
broken down
essential to make
dietary protein -- 20 amino acids -- protein required by body
• Excess amino acids in the diet are decomposed. The
nitrogen is excreted as urea, and the carbon skeletons are
converted to glucose or stored as fat.
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The Genetic Message Expressed II:
Protein Function
18. Proteins have a wide variety of roles
in the body.
• Structural Proteins
• Contractile Proteins
• Regulatory Proteins
• Protective (or defense) Proteins
• Transport Proteins
• Catalytic Proteins
• Storage Proteins
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The Genetic Message Expressed II:
Protein Function
19. Enzymes are catalysts for specific
chemical reactions that occur in living
mater.
• Enzymes are involved in almost every process occurring in
the body.
• Enzymes are the catalysts that speed up chemical
reactions. Without enzymes, most biological reactions
would proceed at an imperceptibly slow rate.
• In a chemical reaction, bonds in the reactants must first be
broken and then re-made as the products are formed.
• If one views this as one continuous process, somewhere in
the middle the energy of the system must be very high.
That is, an energy hill must be climbed in order to get to
the products.
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The Genetic Message Expressed II:
Protein Function
• If this were not the case, the reaction would be very fast
under all conditions.
• Without a catalyst (enzyme) the energy to climb this hill
comes from the kinetic energy of the colliding molecules.
The rate of the reaction can be increased by heating the
solution.
• In the human body, heating the reaction is not an option.
Instead, an enzyme effectively lowers the amount of
energy to climb the hill by changing the way the reaction
occurs in some way.
• The top of the energy hill is called the transition state in
chemical kinetics and an enzyme is said to lower the
energy of the transition state.
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The Genetic Message Expressed II:
Protein Function
• Enzymes are globular proteins with pockets or groves on
their surface called active sites, where the reactant
molecules bind.
• After the reaction is over, the product molecules will be
located in these same sites and are subsequently released.
• The active sites are very specific for which reactant
molecules can bind.
• The forces binding a reactant molecule to an enzyme can
include:
•Hydrogen bonding
•Hydrophobic interactions
•Ionic attractions between ions of unlike charge
•The binding process positions the reactants in exactly the
correct orientation to each other for the reaction to occur.
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The Genetic Message Expressed II:
Protein Function
Copyright W. H. Freeman and Company ·
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The Genetic Message Expressed II:
Protein Function
• All of the enzymes in the body are created in reactions
that themselves require enzymes.
• About 1/3 off all known enzymes require one or more
metal ions such as iron, copper, zinc, manganese,
magnesium, etc. in order to function.
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The Genetic Message Expressed II:
Protein Function
20. Proteins may require additional
molecules to function.
• Simple proteins contain only amino acids.
• Conjugated proteins possess other groups besides amino
acids. These other groups include metal ions, phosphate
groups, sugars, lipids, or other small molecules.
• Some proteins require small complex organic or
organometallic components called coenzymes which
cannot be synthesized by the organism itself.
• Many of the vitamins in our diet supply the coenzymes or
precursors to the coenzymes needed by enzymes in our
body.
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The Genetic Message Expressed II:
Protein Function
• Conjugated proteins containing a sugar unit are called
glycoproteins.
• Glycoproteins are important parts of cell membranes and
are responsible for cell surface properties such as blood
group specificity (ABO).
• Conjugated proteins containing a lipid molecule are called
lipoproteins.
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The Genetic Message Expressed II:
Protein Function
21. Proteins combined with lipids can
contribute to heart disease risk.
• Cholesterol and other lipids are
synthesized in the liver or absorbed
in the intestines and must then be
transported to the places in the body
where they are needed.
• Lipids themselves are not very
soluble in water, so they are bound to
lipoproteins in the blood in order to
be transported.
• Two classes of lipoproteins are
involved: low-density lipoproteins,
LDL’s, and high-density lipoproteins,
HDL’s.
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The Genetic Message Expressed II:
Protein Function
• LDL particles are very cholesterol rich and carry cholesterol
from the liver where it is synthesized to various membranes.
• Too much cholesterol in the body can accumulate in the blood
vessels causing atherosclerosis, which may eventually lead to
a heart attack.
• HDL particles are initially rich in protein and low in
cholesterol. They can bind cholesterol and transport it back
to the liver where it can be broken down. A lack of HDL is
correlated to a higher incidence of heart disease.
• HDL is often called “good cholesterol” and LDL “bad
cholesterol”. A ratio of LDL to HDL of 5 in men indicates an
increased risk for heart disease. The corresponding ratio in
women is 4.5.
• People with high cholesterol levels may be prescribed a class
of drugs called statins which block cholesterol synthesis.
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The Genetic Message Expressed II:
Protein Function
22. If a protein’s shape is altered, its
ability to function is affected.
• When a protein loses its functional shape it is said to be
denatured.
• An example of denaturation occurs in the stomach where
the strong acidic conditions denature the proteins in the
food allowing rapid hydrolysis by digestive enzymes.
• Both heat and extremes in pH will denature most
proteins.
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The Genetic Message in Action
23. Mutations: When things go wrong
• A mutation is a permanent change in the sequence of bases
in a DNA molecule.
• Mutations are passed on to offspring.
• Mutations can occur naturally (at a very low rate) or be
induced by environmental effects such as radiation or toxic
chemicals.
• Chemical agents that cause mutations are called mutagens.
• Teratogens are mutagens that cause birth defects. The
most infamous of these was thalidomide in the late 1950’s.
Thalidomide occurs in left handed and right handed forms.
Unknown at the time, one form prevents miscarriages, but
the other produces birth defects.
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The Genetic Message in Action
• Mutations can change DNA in several ways:
•Substitution mutation - When a single base changes
in the DNA sequence, a single amino acid may change in
the protein sequence.
•Insertion mutation – Three bases are inserted into the
DNA, an additional amino acid is inserted in the protein
sequence.
•Multiple Insertion - A multiple of three bases are
inserted into the DNA; multiple amino acids are inserted
into the protein sequence.
•Single Deletion – Three bases are deleted from the
DNA, a amino acid is deleted from the protein.
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The Genetic Message in Action
•Multiple Deletion – A multiple of three bases is deleted
from the DNA, multiple amino acids are deleted from the
protein.
•Small Inversion – A few groups of three bases reverse
their order, a few amino acids in the protein in reversed
order.
•Large Inversion – Many groups of three bases reverse
their order, large number of amino acids in the protein are
in reversed order.
•Not all mutations produce an observable effect. Silent
mutations replace one amino acid with another of similar
properties so the protein is not affected much.
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The Genetic Message in Action
•Humans have two sets of chromosomes, one set from each
parent. Except for sex linked traits (XY chromosomes) there
are two copies of every gene.
•Usually at least one unmutated copy of each gene is
inherited from one of the parents which “masks” any mutated
copy. In cases such as this the mutation is said to be
recessive.
•In certain cases, mutations provide an advantage to an
organism. The recessive gene for sickle cell anemia confers
an advantage to people infected with malaria.
•When a mutated gene is inherited from both parents,
disease usually results. This often occurs in children from
close relatives and in certain ethnic group.
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The Genetic Message in Action
24. Cloning
• Clones are individuals having exactly the same DNA.
Natural clones are represented by identical twins.
• Many animals have now been cloned, however laboratory
production of cloned humans is not yet possible.
• Cloning of an animal basically involves replacing the
nucleus of an egg cell from a donor with the nucleus of a
body cell from a second donor.
• The science is imperfect and most cloned cells do not
survive. Many of those that do are not healthy.
• Cloning raises ethical and religious questions for many
people.
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The Genetic Message in Action
25. Proteins and DNA can be used as
evidence in legal proceedings.
• Except for the case of identical twins, DNA is unique to a
single person.
• It can theoretically be used to identify an individual with
a very high degree of certainty.
• DNA is very long lasting and older samples from almost
any biological specimen can be successfully analyzed.
• Very small samples can be “amplified” using the PCR or
polymerase chain reaction to obtain a sample large
enough to be analyzed.
• The actual sequences in the DNA that are used to identify
an individual are the repetitive sequence segments
between the segments coding for proteins.
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The Genetic Message in Action
• Long strands of DNA are
first chopped into shorter
pieces using restriction
nucleases.
• These fragments are then
sorted by size and
electrical charge using a
special gel and a strong
electric field.
• Further treatment an
transfer to a nylon
membrane results in a DNA
fingerprint which can be
compared to similar
fingerprints from known
individuals.
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Summarizing the Main Ideas
• The basic units of DNA and RNA are nucleotides.
• Each nucleotide consists of a sugar unit connected to a
phosphate group and a nitrogenous base.
• In DNA the sugar is deoxyribose and the bases are
A,T,C,and G.
• In RNA the sugar is ribose and the bases are A,U,C, and G.
• Alternating phosphate and sugar groups form the backbone
structure of DNA with the bases extending from the
backbone.
• The 3D structure of DNA is a double helix of two chains
running in opposite directions, held together by hydrogen
bonds between the base pairs.
• The principle of complementarity requires that A always
hydrogen bonds to T and C to G. This is the basis for
replication and information transfer.
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Summarizing the Main Ideas
• The linear sequence of bases in DNA carries information in
the form of genes.
• Genes encode the sequences of proteins, which are involve
in all life functions.
• Information in DNA is transcribed into a single
complementary mRNA molecule.
• Triplets of bases on the mRNA called codons specify amino
acids.
• Translation of mRNA base sequence information into protein
amino acid sequences requires ribosomes and tRNA’s.
• Each tRNA has an anticodon which is complementary to a
codon on the mRNA at one end and an amino acid at the
other end.
• The ribosome matches codons on the mRNA to anticodons
on tRNA molecules one codon at a time and extends the
growing polypeptide chain.
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Summarizing the Main Ideas
• Proteins are polyamides produced via condensation
reactions of amino acids.
• Alpha amino acids have a –COOH and a –NH2 group bonded
to a central –CHR- group.
• Short polymers of amino acids are called peptides; longer
ones are called proteins.
• Some conjugated proteins contain groups other than amino
acids.
• The primary structure of a protein is its sequence of amino
acids.
• The secondary structure of a protein is the shape adopted
the polymer’s backbone. Examples are the alpha helix and
the beta pleated sheet.
• The tertiary structure of a protein is it overall folding.
• The quaternary structure of a protein is its arrangement of
subunits relative to each other.
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Summarizing the Main Ideas
• The unfolding of a protein from its native form is called
denaturation.
• Different proteins have different functions in the body.
• Enzymes are proteins that catalyze chemical reactions.
• A reactant molecule, the substrate, fits into the active site
of an enzyme.
• During the reaction, partial bonds form between the
substrate and the enzyme which lowers the amount of
energy required before the substrate can react.
• Lipoproteins are a collection of protein molecules
surrounding a lipid particle. They provide a mechanism for
the transport of insoluble hydrophobic molecules in the
bloodstream.
• Mutations are changes in the DNA sequence coding for
particular proteins.
Copyright W. H. Freeman and Company ·
New York
Summarizing the Main Ideas
• Mutations can alter the shape and function of protein
molecules.
• Silent mutations do not alter overall protein function.
• Insertions or deletions may affect protein function minimally
or may render it inactive.
• An mutation rendering a protein inactive is lethal if the
protein is required for life.
• Mutations are the basis for many diseases.
• Understanding of the genetic code has made cloning and
DNA analysis possible.
• Cloning uses genetic material to make exact copies of
organisms.
• DNA analysis allows forensic investigators o use DNA from
biological samples to identify, convict, or exonerate
individuals.
Copyright W. H. Freeman and Company ·
New York