28.2 Base Pairing in DNA
3 min read•may 7, 2024
's structure is a marvel of nature. Its and unique features ensure genetic information is stored and passed on accurately. This intricate design allows for the stability and fidelity crucial in biological processes.
The of molecular genetics explains how genetic info flows in cells. It outlines three key processes: DNA , to , and translation to proteins. This fundamental concept ties together the roles of DNA, RNA, and proteins in life.
DNA Structure and Function
Base-pairing rule in DNA
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- DNA composed of two strands form a
- Each consists of a , a sugar, and a nitrogenous base () (, , , or )
- Complementary base pairing occurs between nitrogenous bases on opposite strands
- Adenine (A) pairs with thymine (T) via two hydrogen bonds (A=T)
- Guanine (G) pairs with cytosine (C) via three hydrogen bonds (G≡C)
- Specific base pairing ensures stability and fidelity of DNA double helix allows for accurate replication and transcription
Features of DNA double helix
- Right-handed spiral with diameter of ~2 nm
- Two polynucleotide strands run antiparallel with 5' end and 3' end
- Sugar-phosphate backbones on outside of helix, nitrogenous bases face inward
- and important for protein interactions (transcription factors)
- Complete turn every 10.5 base pairs, with rise of 3.4 Å per base pair
- Stacking of aromatic rings of nitrogenous bases contributes to stability via hydrophobic interactions and stacking ()
DNA Base Classification and Structure
- Nucleobases in DNA are classified into two categories:
- Purines: larger, double-ring structures (adenine and guanine)
- Pyrimidines: smaller, single-ring structures (thymine and cytosine)
- describes the specific base pairing between purines and pyrimidines in DNA
- Base stacking interactions between adjacent base pairs contribute to DNA stability
Central Dogma of Molecular Genetics
Central dogma of molecular genetics
- Describes flow of genetic information within biological system
- DNA transcribed into RNA, which is then translated into proteins
- Three fundamental processes:
- Replication
- Cell makes exact copy of genetic material before cell division
- Semiconservative, each daughter DNA molecule contains one original strand and one newly synthesized strand
- Ensures genetic information passed on to daughter cells (mitosis, meiosis)
- Transcription
- Synthesis of RNA from DNA template catalyzed by RNA polymerase
- Complementary RNA strand using one DNA strand as template
- Resulting RNA molecule called () carries genetic information from DNA to ribosomes
- Also produces other RNA types (, rRNA, miRNA)
- Translation
- Synthesis of proteins using genetic information carried by mRNA
- Ribosomes read mRNA sequence in triplets called codons, each coding for specific amino acid
- molecules carry specific amino acids, recognize codons, deliver amino acids to growing polypeptide chain
- Sequence of amino acids in polypeptide chain determines structure and function of resulting protein (enzymes, structural proteins, signaling molecules)
- Replication
Key Terms to Review (33)
Adenine: Adenine is a purine-based nitrogenous base that is one of the four fundamental building blocks of nucleic acids, including DNA and RNA. It plays a crucial role in various biochemical processes and is closely associated with the topics of polycyclic aromatic compounds, carbohydrates, and nucleic acids.
Antiparallel: Antiparallel refers to the orientation of the two strands of DNA, where the sugar-phosphate backbones run in opposite directions. This arrangement is crucial for the stability and function of the DNA molecule.
Base Stacking: Base stacking refers to the interactions between adjacent DNA or RNA base pairs that contribute to the stability and structure of the nucleic acid molecule. This non-covalent interaction occurs due to the overlap of the planar aromatic rings of the nitrogenous bases, creating a stacking effect that helps maintain the helical shape of the double helix.
Central Dogma: The Central Dogma is the fundamental principle in molecular biology that describes the flow of genetic information within a biological system. It states that the genetic information stored in DNA is transcribed into RNA, which is then translated into proteins, the functional molecules that carry out the majority of activities within cells.
Codon: A codon is a sequence of three consecutive nucleotides in a molecule of messenger RNA (mRNA) that specifies the amino acid to be inserted at that position during protein synthesis. Codons are the fundamental units that direct the translation of genetic information from mRNA into the primary structure of a polypeptide chain.
Complementary Base Pairing: Complementary base pairing is a fundamental principle in molecular biology, where specific nucleic acid bases form pairs with each other to maintain the structure and function of genetic material, such as DNA and RNA. This concept is central to understanding the storage, replication, and expression of genetic information across various biological topics.
Cytosine: Cytosine is a pyrimidine-based nitrogenous base that is one of the four main components of nucleic acids, including DNA and RNA. It plays a crucial role in the structure and function of these genetic materials across various topics in organic chemistry.
Deoxyribonucleic acid (DNA): DNA is a molecule that contains the instructions an organism needs to develop, live, and reproduce. It is composed of two long strands forming a double helix structure, where sequences of four types of nucleotides encode genetic information.
Deoxyribose: Deoxyribose is a monosaccharide, a type of simple sugar, that serves as the primary structural component of the backbone of deoxyribonucleic acid (DNA) molecules. It is an essential building block for the genetic material found in all living organisms.
DNA: DNA, or deoxyribonucleic acid, is the genetic material that carries the instructions for the development and functioning of living organisms. It is a complex molecule that stores and transmits genetic information, playing a crucial role in various aspects of organic chemistry, including chirality, carbohydrates, and nucleic acids.
Double helix: A double helix is the structure formed by two strands of DNA wound around each other, resembling a twisted ladder. This configuration allows for the efficient storage of genetic information and its accurate replication.
Double Helix: The double helix is the characteristic structure of DNA (deoxyribonucleic acid), which is the genetic material found in the nucleus of cells. It consists of two complementary strands of nucleotides that wind around each other in a spiral formation, resembling a twisted ladder.
Guanine: Guanine is a purine-based nitrogenous base that is one of the four primary components of nucleic acids, including DNA and RNA. It is a crucial element in the genetic makeup of all living organisms, playing a vital role in various biological processes.
Hydrogen Bond: A hydrogen bond is a special type of dipole-dipole attraction that occurs when a hydrogen atom covalently bonded to a highly electronegative element, such as nitrogen, oxygen, or fluorine, is attracted to another nearby highly electronegative element. This intermolecular force plays a crucial role in the base pairing of DNA molecules.
Major Groove: The major groove is a structural feature of the DNA double helix, referring to the wider and deeper channel that runs along the length of the DNA molecule. This groove is an important aspect of the DNA structure and plays a crucial role in the binding and recognition of DNA by various proteins and enzymes.
Messenger RNA: Messenger RNA (mRNA) is a single-stranded molecule that carries the genetic instructions from the nucleus to the ribosomes in the cytoplasm, where proteins are synthesized. It acts as a template for the translation of genetic information into functional proteins, playing a crucial role in the central dogma of molecular biology.
Minor Groove: The minor groove is a structural feature of DNA, referring to the narrower and more compressed side of the double helix. It is one of the two grooves formed by the twisting of the DNA molecule, the other being the major groove.
MRNA: mRNA, or messenger RNA, is a single-stranded molecule that carries the genetic instructions from the nucleus to the ribosomes in the cytoplasm, where protein synthesis occurs. It serves as a template for the production of specific proteins within the cell.
Nucleobase: A nucleobase, also known as a nitrogenous base, is a fundamental component of nucleic acids, such as DNA and RNA. Nucleobases are the building blocks that store and transmit genetic information within living organisms.
Nucleotide: A nucleotide is the basic structural unit of nucleic acids, such as DNA and RNA. It consists of a nitrogenous base, a five-carbon sugar, and a phosphate group. Nucleotides are essential in various biological processes, including DNA replication, transcription, and translation.
Phosphate Group: A phosphate group is a chemical structure consisting of one phosphorus atom covalently bonded to four oxygen atoms. It is a fundamental component in various biomolecules, playing crucial roles in energy storage, cell signaling, and the structural integrity of biological macromolecules.
Polynucleotide: A polynucleotide is a large biomolecule composed of multiple nucleotides linked together in a long, continuous chain. Polynucleotides are the fundamental building blocks of nucleic acids, such as DNA and RNA, which store and transmit genetic information within living organisms.
Purine: Purines are a class of heterocyclic aromatic organic compounds that consist of a pyrimidine ring fused to an imidazole ring. They are essential components of nucleic acids, such as DNA and RNA, and play crucial roles in various biological processes.
Pyrimidine: Pyrimidine is a heterocyclic aromatic organic compound containing two nitrogen atoms in the six-membered ring structure. It is a fundamental component of important biomolecules such as nucleic acids and certain vitamins, and is also found in various heterocyclic compounds.
Replication: Replication is the process by which a DNA molecule is copied, producing two identical DNA molecules from a single parent molecule. This process is essential for cell division, growth, and the transmission of genetic information from one generation to the next.
Ribosome: A ribosome is a complex molecular machine found within all living cells that is responsible for the synthesis of proteins, which are essential for the structure, function, and regulation of the body\'s tissues and organs. Ribosomes are central to the process of translation, where the genetic information encoded in messenger RNA (mRNA) is used as a template to direct the assembly of amino acids into polypeptide chains, ultimately forming functional proteins.
RNA: RNA, or ribonucleic acid, is a crucial biomolecule that plays a central role in the storage and expression of genetic information within cells. It is closely related to DNA, but with some key structural and functional differences that make it an essential component in various biological processes.
Sugar-Phosphate Backbone: The sugar-phosphate backbone is the structural foundation of nucleic acids, such as DNA and RNA. It consists of a repeating pattern of sugar (deoxyribose or ribose) molecules linked together by phosphate groups, forming the backbone upon which the nitrogenous bases are attached.
Thymine: Thymine is a pyrimidine-based nitrogenous base that is one of the four essential components of DNA, along with adenine, cytosine, and guanine. It plays a crucial role in the structure and function of nucleic acids, particularly in the context of aromatic heterocycles, carbohydrates, and nucleotides and nucleic acids.
Transcription: Transcription is the process by which the genetic information encoded in a DNA sequence is copied into a complementary RNA molecule. This RNA molecule, known as messenger RNA (mRNA), serves as a template for the synthesis of proteins, which are the functional molecules that carry out the majority of the cell's activities.
Transfer RNA (tRNA): Transfer RNA, or tRNA, is a type of RNA molecule that plays a crucial role in the process of protein synthesis by facilitating the translation of genetic information from messenger RNA (mRNA) into the corresponding amino acid sequence of a polypeptide chain. tRNA acts as an adapter, linking the genetic code to the amino acids that will be assembled into proteins.
TRNA: Transfer RNA (tRNA) is a type of RNA molecule that plays a crucial role in the process of protein synthesis within cells. tRNA acts as an adapter molecule, translating the genetic code stored in messenger RNA (mRNA) into the specific sequence of amino acids that make up a protein.
Watson-Crick Model: The Watson-Crick model is a structural model that describes the double-helix configuration of DNA molecules. It was proposed by James Watson and Francis Crick in 1953 and is a fundamental concept in understanding the structure and function of nucleic acids.