Polymeric molecules in which the repeating units are nucleotides
Types of nucleic acids
Deoxyribonucleic acids (DNA)
Ribonucleic acids (RNA)
Functions of DNA and RNA
DNA - transfer of genetic information
RNA - synthesis of proteins
Nucleic acid building blocks
Pentose sugar (ribose or deoxyribose)
Nitrogen-containing base (purine or pyrimidine derivative)
Phosphate group
Nitrogen-containing bases
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
Uracil (U)
Nucleoside
Compound formed from a pentose sugar and a purine or pyrimidine base derivative
Nucleotide
Nucleoside to which a phosphate group has been added
Nucleotide
Monomers for nucleic acid polymers
Primary nucleic acid structure
Backbone is a constant alternating sequence of sugar and phosphate groups, with a nitrogen-containing base attached to each sugar unit
Complementary bases
Specific pairs of bases in nucleic acid structures that hydrogen-bond to each other
Secondary DNA structure
Two polynucleotide chains coiled around each other in a double-helix arrangement, held together by hydrogen bonding between complementary pairs of bases (A with T, C with G)
DNA replication
Two strands of a parent DNA double helix separate and act as templates for the synthesis of new chains using the principle of complementary base pairing
Chromosome
Structure consisting of an individual DNA molecule bound to a group of proteins
Types of RNA molecules
Ribosomal RNA (rRNA)
Messenger RNA (mRNA)
Heterogeneous nuclear RNA (hnRNA)
Transfer RNA (tRNA)
Small nuclear RNA (snRNA)
Transcription
Genetic information encoded in the base sequence of DNA is copied into hnRNA/mRNA molecules
Gene
Portion of a DNA molecule that contains the base sequences needed for the production of a specific hnRNA/mRNA molecule, with exons containing genetic information and introns not conveying genetic information
Codon
Three-nucleotide sequence in mRNA that codes for a specific amino acid needed during protein synthesis
Genetic code
All the mRNA codons that specify either a particular amino acid or the termination of protein synthesis
Anticodon
Three-nucleotide sequence in tRNA that binds to a complementary sequence (a codon) in mRNA
Translation
Codons in mRNA are translated into amino acid sequences of new proteins, involving interactions between the codons of mRNA and the anticodons of tRNA
Types of mutations
Point mutation - one base in a DNA sequence is replaced with another base
Frameshift mutation - insertion or replacement of a base in a DNA sequence
Recombinant DNA
Synthesized by splicing a segment of DNA, usually a gene, from one organism into the DNA of another organism
Polymerase chain reaction
Method for rapidly producing many copies of a DNA sequence
Nucleoside
A two-subunit molecule in which a pentose sugar is bonded to a nitrogen containing heterocyclic base
Nucleoside formation
1. Base
2. Sugar
3. Water
Nucleoside formation
The base is always attached to C1' of the sugar (the anomeric carbon atom) in a β-configuration
For purines, attachment is through N9; for pyrimidines, N1 is involved
A molecule of water is formed as the two molecules bond together
RNA nucleosides
ribose-adenine
ribose-cytosine
ribose-guanine
ribose-uracil
DNA nucleosides
deoxyribose-adenine
deoxyribose-cytosine
deoxyribose-guanine
deoxyribose-thymine
Nucleoside naming
Pyrimidine bases use the suffix -idine
Purine bases use the suffix -osine
The prefix deoxy- indicates deoxyribose sugar
Nucleotide
A nucleoside with a phosphate group bonded to the pentose sugar
Nucleotide formation
1. Nucleoside
2. Phosphate group
3. Water
Nucleotide formation
The phosphate group is attached to the sugar at the C5' position through a phosphoesterlinkage
A molecule of water is produced in the process
Nucleotides
Adenosine 5'-monophosphate (AMP)
Guanosine 5'-monophosphate (GMP)
Cytidine 5'-monophosphate (CMP)
Uridine 5'-monophosphate (UMP)
Deoxyadenosine 5'-monophosphate (dAMP)
Deoxycytidine 5'-monophosphate (dCMP)
Deoxyguanosine 5'-monophosphate (dGMP)
Deoxythymidine 5'-monophosphate (dTMP)
Ribonucleic Acid (RNA)
A nucleotide polymer in which each of the monomers contains ribose, phosphate group, and one the heterocyclic bases: adenine, guanine, cytosine, or uracil
Deoxyribonucleic Acid (DNA)
A nucleotide polymer in which some of the monomers contain deoxyribose, phosphate group and one of the heterocyclic bases: adenine, guanine, cytosine and thymine
Nucleic Acid Backbone
The alternating sugar-phosphate chain in nucleic acid structure
Constant through the entire nucleic acid structure
For DNA molecules, it consist of alternating phosphate and deoxyribose sugar units
For RNA molecules, it consists of alternating phosphate and ribose sugar units
Primary Nucleic Acid Structure
The sequence in which nucleotides are linked together in a nucleic acid
Depends only on the sequence of bases present
Important Points about Nucleic Acid Structure
Each nonterminal phosphate group of the sugar-phosphate backbone is bonded to sugar molecules through a 3',5'-phosphodiester linkage
A nucleotide chain has directionality. The 5'end normally carries a free phosphate group attached to the 5' carbon atom. The 3' end normally has a free hydroxyl group attached to the 3' carbon atom
Each nonterminal phosphate group in the backbone of a nucleic acid carries a 1- charge
DNA Double Helix
Involves two polynucleotide strands coiled around each other in a manner similar to a spiral staircase
The sugar-phosphate backbone as the outside banisters of the spiral staircase
The bases (side chains) extend inward toward the bases of the other strand
The two strands are connected by hydrogen bonds between their bases
The two strands is antiparallel–as they run in opposite direction: one runs in the 5' to 3' direction, the other runs in 3' to 5' direction
Two strands of DNA in a double helix are not identical —they are complementary
Base Pairing
One small base (a pyrimidine) and one large base (a purine)
Most favorable combinations that normally occur in DNA are the A–T and G—C pairing