Polymerization and Sequence
Storage of information and function are
based on very large molecules
(macromolecules) built from sequentially
added subunits (each of which is a
moderately sized molecule).
Lecture 6 Exam 1
UIC BioS 101 Nyberg 1
►I I have assigned chapters 3 & 4 as the
reading for this lecture. There is a lot of info
in those chapters (most(
most is also covered in BioS 100).
►I I recommend concentrating your studying
on the understanding the significance of the
sequence order in nucleic acids and
Lecture 6 Exam 1 UIC BioS 101 Nyberg 2
►Reading and storing biological information is
done linearly and directionally.
►Linear means that there are no branches or
►There is a beginning and an end in
biological information expression.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 3
►Biologically important macromolecules are
polymers built through linking of subunits,
►In biological polymers the order of the
subunits (parts) is critical. Biological
‘information’ is read linearly and
directionally (like written language).
Lecture 6 Exam 1 UIC BioS 101 Nyberg 4
Major Biological Polymers
and RNA are nucleic acids that store
information in the sequence of bases
attached to the ‘backbone’ of a chain.
►A Protein is a specific sequence of amino
acids linked together linearly. The sequence
of amino acids is known as the primary
structure of the protein.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 5
nucleotide is the subunit of nucleic
►A A single nucleotide has 3 parts:
• one Nitrogenous base
• one 5 carbon sugar
• Phosphate (1 to 3)
►The subunits are linked together with a
Lecture 6 Exam 1 UIC BioS 101 Nyberg 6
►All nucleotides have a nitrogenous base
attached to the sugar and a phosphate
attached to the sugar at a different place.
►The sugar in DNA is different than RNA
• DNA sugar is deoxyribose
• RNA sugar is ribose
►The nitrogenous bases are of two types,
purines and pyrimidines.
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►DNA has only four different nitrogenous
bases: Cytosine (C)(
) and Thymine (T)(
pyrimidines, , Adenine (A)(
) and Guanine (G)(
►DNA is actually two very long molecules
held together by many hydrogen bonds
between a purine on one strand and a
pyrimidine on the other.
►A pairs with T; G pairs with C
Lecture 6 Exam 1 UIC BioS 101 Nyberg 8
A segment of DNA
a DNA double strand
Each line represents consecutive bases in a strand
(=molecule) of DNA. The two strands are held
together by hydrogen bonds.
The strands have a direction when one looks at the
chemical details. By convention the top strand is
5’ to 3’ 3 and the bottom strand is therefore 3’ 3 to 5’. 5
Lecture 6 Exam 1 UIC BioS 101 Nyberg 9
►Because of base pairing, knowing the
sequence of one strand tells one the
sequence of the other DNA strand, so often
the sequence of only one is given (5’ to left).
►When the strands match they are said to be
►The two strands of double stranded DNA will
separate (melt) when the temperature is
raised (75 to 80° C). They match up perfectly
when the temp is slowly cooled.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 10
►Question: How many different DNA
sequences are there that are 5 bases long?
►There are 4 ‘letters’ in the DNA ‘alphabet’.
►Like languages the letters are read in a
direction (AT is different than TA)
►Solution: 4 possible choices for 1 st position,
4 possible for 2 nd , etc., so 4x4x4x4x4=1024
= 4 5 = 2 10 .
Lecture 6 Exam 1 UIC BioS 101 Nyberg 11
won’t t match by chance
►If one has a sequence 20 bases long, there
are 4 20 different possible sequences, or
somewhat more than 10 12 , or a thousand
►Only one out of the 10 12 possible will be an
exact match to that sequence. Only 60
sequences (20 positions x 3 possible nonmatches
per position) will have one nonmatch.
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Comparing DNA sequences
► Species B GGGTACCTATGCGAATATTCAT
BC different ** * *
► Species C CAGTGCCTAAGCGAATATTCAT
AC different * * *
► Species A CGGTACCTATGCGAATATTCAT
AB different *
Among these 3 species, A & B are closest.
Their sequences differ only at position 1.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 13
Long Similar Sequences
►Long sequences in different organism that
are similar probability have a common
origin. The probabilities that two sequences
are similar through chance (independent
origins) are very low.
►Phylogeny is inferred by measuring
Lecture 6 Exam 1 UIC BioS 101 Nyberg 14
Probing for a match
►The ability to take a piece of known sequence
and mix it with diverse pieces and then
determine if any piece in the mix is an exact
match is the source of the power of DNA
►Ability to find exact complement out of
billions of combinations allows one to find ‘a
needle in a haystack’.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 15
Human Genetic Uniqueness
► Though we share most sequences with all other
humans, each individual can be uniquely identified
genetically (with the exception of identical twins).
► DNA survives outside of the body and usually
some long pieces can be recovered from bits of
tissue a 100 years old.
► DNA testing has resulted in the exoneration of
many individuals convicted of crimes based on
techniques available before it was possible to run
DNA tests (especially true in rape cases).
Lecture 6 Exam 1 UIC BioS 101 Nyberg 16
Separating DNA by size
►The phosphate groups in the DNA backbone
have a negative charge.
►Gel electrophoresis separates DNA pieces by
their length. Shorter lengths migrate more
quickly through the ‘maze’ of gel strands.
►The nucleic acid molecule migrate toward
the positive pole of an electrical gradient.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 17
RNA, another nucleic acid
►RNA has the ribose sugar instead of
►RNA has Uracil (U)) in place of Thymine as a
►The most important difference is that RNA
molecules are normally single stranded
rather than double stranded like DNA.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 18
Types of RNA
►Messenger RNA carries the information
necessary to build a protein.
►Transfer RNA is connected to amino acids
and assures the order of amino acids as the
message is translated.
►Ribosomal RNA is the major component of
the ribosome, the organelle on which
translation takes place.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 19
Folding single strands
►Single-stranded RNA often has regions (6-
12 bases long) in different places that would
be complementary if the molecule folded
back on itself.
►The folds create double-stranded regions
and allow a greater diversity of shape in
RNA (compared to DNA).
►RNA molecules are shorted than DNA and
take on diverse shapes and configurations.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 20
The Central Dogma
►DNA makes DNA = replication
►DNA makes RNA = transcription
►RNA makes protein = translation
►DNA stores information and allows it to be
►Proteins perform function.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 21
►As with DNA, proteins are made up as a
sequence of subunits. The order of the
amino acids determines the properties of
►Though the first molecules sequenced were
proteins, today it is much easier to
sequence nucleic acids. The amino acid
sequence can be determined from the DNA.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 22
►All amino acids have a central carbon that is
• A hydrogen
• An amino group –NH
• A carboxyl acid group –COOH
• A ‘side chain’ of which there are 20 different
Lecture 6 Exam 1 UIC BioS 101 Nyberg 23
►The 3D shape of the protein is what enables
the protein to perform specialized functions.
►The side chains of amino acids have
diversity in polarity, charge and elemental
composition. That diversity is what creates
the possibility of fine adjustments to shape.
Lecture 6 Exam 1 UIC BioS 101 Nyberg 24
►If there are 20 possible amino acids per
position, what is the minimum length of a
polypeptide (# of units) that would have
over 1 million possible different sequences?
Lecture 6 Exam 1 UIC BioS 101 Nyberg 25
► Base pairing
► Genetic uniqueness
► Primary structure
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