SC BIOL 1000
Section 1: DNA structure
Our focus: the structure of DNA, and on the process that enables every organism to develop, function,
and reproduce: DNA replication (from one to two DNA).
o DNA (store the information, very precise) -> zygote (could become the identical twins)
o DNA replication is a key aspect of cell division resulting in containing the DNA information in every
single cell.
Why is DNA found in every cell?
o DNA contains the instructions for every single thing from how and when to make protein, and other
molecules each cell needs in order to do its job.
o Our body is composed of protein and instruction about protein is basically everything.
o Thus, having DNA’s instruction in every single cell means each cell can make th precise proteins in
needs, when it needs them.
o Transcription and translation = a complex process that the cell reads and acts on the information in
DNA
o The information stored in DNA differs among organisms.
o The difference between eukaryotic and prokarotic DNA
o The specific infromation contained within DNA
o The location of the DNA within each cell
DNA in cells
Eukaryotes Prokaryotes
Nucleus Yes No
Membrane-bound organelles Yes No
Location of DNA Mitochondria and chloroplasts Cytoplasm
inside the nucleus
The basic structure of DNA
o Two strands, wrap around
o Each of them consist of nucleotides: A, G, C, T (A-T, C-G) : each – bases, A-T: C-G – base pair
o DNA : dioxyribose, a phosphate group, and nitrogenous base (also called a base)
§ Dioxyribose: 5 carbon atoms, 5’ has phosphate group attached, 1’ has attached to nitrogenous
base, and 3’ with OH group
§ Four bases: A, T, C, G
§ A and G (purines) contain two carbon rings
§ T and C (pyrimidines) contain one ring
§ Purine always pair with pyrimidines and vice versa.
o Chemical bonds in DNA
o One end 5’ has phosphate at the top, the other strand 3’ has additional nucleotide attached.
o When building incomplete strand, polymerase (enzyme) comes and deoxynucleotide triphosphate
(DNTP) attaches to the ones that is complementary for the opposite side of DNA. - the energy is
used to build new base each.
o Phosphodiester bonds in same line of the DNA.
o Direction: 5’ to 3’
, § Means, DNA polymerase always adds nucleotides onto the 3’ end of the DNA strand.
DNA is a polymer
o Monomer of DNA: nucleotides
o dNTPs supply energy to polymerase DNA, and they become nucleotides in the DNA.
Hydrogen bonds and base pairing
o DNA construction has two bonding: one with covalent bonds on the same line of DNA; hydrogen bonds
for the across each other. Hydrogen bonds hold the two strands of DNA together.
o Complementary base: A-T, C-G; A-T has 2 hydrogen bonds, and C-G has 3 hydrogen bonds
o Base pair : A, C, G, T
o Covalent bonds are stronger than hydrogen bonds
o Base Pair Bond Strength
o Between AT and CG, CG is stronger than AT bonds.
o DNA sequence
o The bonds that hold DNA together make DNA a stable molecule.
o And the stability is important in DNA functioning.
o The sequence of bases in a strand of DNA encodes inforation for the cell.
o The sequence of bases provides instructions for how and when to make the proteins that are
needed for the organism to live, reproduce, interact with environment, and so on.
o Changing the sequence bases in DNA can change the meaning of the instructions.
o DNA sequences goes from 5’ end to 3’ end
Protein interact with DNA
o Most of the DNA in the cell is wound around proteins called histones
o DNA is a more flexible string.
o The wounded-up package by histone allows DNA to be more compacted.
o Packaging DNA like this allows it to be moved around during cell division.
o Adjectives to describe DNA: Packaged, compacted, flexible, stable, double-stranded
o Many proteins besides histones attach to DNA.
o Some proteins can attach to specific nucleotide sequences to initiate DNA replication or to
regulate transcription.
o To attach to DNA, proteins have complementary surface shapes and chemistry to particular DNA
locations.
o Linear vs. Circular DNA
o Linear – 5’ and 3’ end with each strand, eukaryotic cells
* o Circular – DNA in prokaryotic cells, bacterial cell, mitochondria and chloroplasts
§ No 5’ and 3’ end but 5’ and 3’ directions.
§ Reminder: phosphodiester bonds form between 3’ hydroxyl (OH) end of one nucleotide and 5’
phosphate group next.
§ Directionality of these bonds dictate the 5’ and 3’ directions in DNA’s strand.
§ Basic polymer structure is the same as linear DNA: antiparellel with 5’ and 3’ direction.
§ Interaction with other cellular proteins and is replicated in the same basic manner as linear DNA.
o DNA vs. RNA
o DNA – stable
o RNA – closely related to DNA, similar structure as DNA
§ A-U : pyrimidine (U replace T from DNA);
§ 2’ carbon is attached to the hydroxyl group instead of hydrogen atom.
Section 1: DNA structure
Our focus: the structure of DNA, and on the process that enables every organism to develop, function,
and reproduce: DNA replication (from one to two DNA).
o DNA (store the information, very precise) -> zygote (could become the identical twins)
o DNA replication is a key aspect of cell division resulting in containing the DNA information in every
single cell.
Why is DNA found in every cell?
o DNA contains the instructions for every single thing from how and when to make protein, and other
molecules each cell needs in order to do its job.
o Our body is composed of protein and instruction about protein is basically everything.
o Thus, having DNA’s instruction in every single cell means each cell can make th precise proteins in
needs, when it needs them.
o Transcription and translation = a complex process that the cell reads and acts on the information in
DNA
o The information stored in DNA differs among organisms.
o The difference between eukaryotic and prokarotic DNA
o The specific infromation contained within DNA
o The location of the DNA within each cell
DNA in cells
Eukaryotes Prokaryotes
Nucleus Yes No
Membrane-bound organelles Yes No
Location of DNA Mitochondria and chloroplasts Cytoplasm
inside the nucleus
The basic structure of DNA
o Two strands, wrap around
o Each of them consist of nucleotides: A, G, C, T (A-T, C-G) : each – bases, A-T: C-G – base pair
o DNA : dioxyribose, a phosphate group, and nitrogenous base (also called a base)
§ Dioxyribose: 5 carbon atoms, 5’ has phosphate group attached, 1’ has attached to nitrogenous
base, and 3’ with OH group
§ Four bases: A, T, C, G
§ A and G (purines) contain two carbon rings
§ T and C (pyrimidines) contain one ring
§ Purine always pair with pyrimidines and vice versa.
o Chemical bonds in DNA
o One end 5’ has phosphate at the top, the other strand 3’ has additional nucleotide attached.
o When building incomplete strand, polymerase (enzyme) comes and deoxynucleotide triphosphate
(DNTP) attaches to the ones that is complementary for the opposite side of DNA. - the energy is
used to build new base each.
o Phosphodiester bonds in same line of the DNA.
o Direction: 5’ to 3’
, § Means, DNA polymerase always adds nucleotides onto the 3’ end of the DNA strand.
DNA is a polymer
o Monomer of DNA: nucleotides
o dNTPs supply energy to polymerase DNA, and they become nucleotides in the DNA.
Hydrogen bonds and base pairing
o DNA construction has two bonding: one with covalent bonds on the same line of DNA; hydrogen bonds
for the across each other. Hydrogen bonds hold the two strands of DNA together.
o Complementary base: A-T, C-G; A-T has 2 hydrogen bonds, and C-G has 3 hydrogen bonds
o Base pair : A, C, G, T
o Covalent bonds are stronger than hydrogen bonds
o Base Pair Bond Strength
o Between AT and CG, CG is stronger than AT bonds.
o DNA sequence
o The bonds that hold DNA together make DNA a stable molecule.
o And the stability is important in DNA functioning.
o The sequence of bases in a strand of DNA encodes inforation for the cell.
o The sequence of bases provides instructions for how and when to make the proteins that are
needed for the organism to live, reproduce, interact with environment, and so on.
o Changing the sequence bases in DNA can change the meaning of the instructions.
o DNA sequences goes from 5’ end to 3’ end
Protein interact with DNA
o Most of the DNA in the cell is wound around proteins called histones
o DNA is a more flexible string.
o The wounded-up package by histone allows DNA to be more compacted.
o Packaging DNA like this allows it to be moved around during cell division.
o Adjectives to describe DNA: Packaged, compacted, flexible, stable, double-stranded
o Many proteins besides histones attach to DNA.
o Some proteins can attach to specific nucleotide sequences to initiate DNA replication or to
regulate transcription.
o To attach to DNA, proteins have complementary surface shapes and chemistry to particular DNA
locations.
o Linear vs. Circular DNA
o Linear – 5’ and 3’ end with each strand, eukaryotic cells
* o Circular – DNA in prokaryotic cells, bacterial cell, mitochondria and chloroplasts
§ No 5’ and 3’ end but 5’ and 3’ directions.
§ Reminder: phosphodiester bonds form between 3’ hydroxyl (OH) end of one nucleotide and 5’
phosphate group next.
§ Directionality of these bonds dictate the 5’ and 3’ directions in DNA’s strand.
§ Basic polymer structure is the same as linear DNA: antiparellel with 5’ and 3’ direction.
§ Interaction with other cellular proteins and is replicated in the same basic manner as linear DNA.
o DNA vs. RNA
o DNA – stable
o RNA – closely related to DNA, similar structure as DNA
§ A-U : pyrimidine (U replace T from DNA);
§ 2’ carbon is attached to the hydroxyl group instead of hydrogen atom.
