A1.2 Nucleic Acids
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Structure of Nucleotides
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Today, we will talk about nucleotides, which are the building blocks of nucleic acids. Can someone tell me the three components of a nucleotide?
Is it the nitrogenous base, the sugar, and the phosphate?
Exactly! Nucleotides consist of a nitrogenous base, a pentose sugar, and a phosphate group. Let's break them down into more detail. What are the two types of nitrogenous bases?
Purines and pyrimidines?
Correct! Purines include adenine and guanine, while pyrimidines include cytosine, thymine, and uracil. Remember, 'Cut The Py' for pyrimidinesβCytosine, Thymine, and Uracil. Now, how does the structure of deoxyribose differ from ribose?
Deoxyribose doesn't have an oxygen atom at the 2' carbon, right?
Exactly! This difference in sugar makes DNA more stable. Great job! Let's summarize: Nucleotides are made up of a nitrogenous base, a sugar, and a phosphate group. Purines and pyrimidines are types of bases, and the difference between deoxyribose and ribose is important for DNA stability.
Polynucleotide Structure
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Now that we understand nucleotides, let's discuss how they link together to form polynucleotides. Who can explain what a phosphodiester bond is?
It's the bond formed between the phosphate group of one nucleotide and the hydroxyl group of another nucleotide's sugar?
Correct! This bond forms the sugar-phosphate backbone. Can anyone explain what we mean by the directionality of the DNA strands?
One end is the 5' end, and the other is the 3' end. They run antiparallel to each other in the double helix.
Exactly! Remember the phrase '5 to 3 in DNA,' which helps us remember how DNA is structured. This distinct directionality is important for processes like replication and transcription. What are the key features of the double helix?
It has base pairing with A-T and C-G, and there are major and minor grooves for protein binding.
Fantastic! The base pairing stabilizes the structure, and the grooves are critical for DNA-protein interactions. In summary, polynucleotides are formed through phosphodiester bonds creating a sugar-phosphate backbone with directionality.
Functions of Nucleic Acids
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So we know what nucleic acids are made of and how they are structured. Now letβs discuss their functions. What is the main role of DNA in cells?
DNA stores genetic information.
Right! And how is this information passed on to make proteins?
Through transcription into RNA and then translation into proteins.
Perfect! Remember 'TRAP' for the flow of information: Transcription, RNA, Assembly, Protein. Can anyone name the different types of RNA and their functions?
We have mRNA, tRNA, and rRNA. mRNA carries the code, tRNA brings the amino acids, and rRNA is part of the ribosome.
Well done! And letβs not forget about regulatory types of RNA, like miRNA and siRNA. They play a role in gene regulation. To wrap up, nucleic acids are vital for storing, transmitting, and regulating genetic information in cells.
Inheritance and Evolutionary Significance
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We are nearing the end of our discussion. Now, how do nucleic acids relate to inheritance?
They carry the genetic codes that parents pass down to their offspring.
Exactly! And how about the evolutionary perspective?
The universal genetic code shows we share a common ancestor, right? Mutations and variations drive evolution.
Correct again! The code is nearly universal among organisms, highlighting our evolutionary relationships. Can anyone summarize how mutations contribute to diversity?
Mutations create genetic variations, which can lead to adaptations, enabling evolution by natural selection.
Great summary! In closing, nucleic acids are not only essential for cellular functions but also play a crucial role in heredity and the evolution of life on Earth.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The section covers the composition and structure of nucleotides, detailing the differences between DNA and RNA, their respective functions in genetic information storage and transmission, and the significance of nucleic acids in cellular processes and evolution.
Detailed
Nucleic Acids Overview
Nucleic acids are essential biomolecules that store and transmit genetic information in all living organisms. The main types of nucleic acids are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). This section elaborates on the fundamental unit of nucleic acids, the nucleotide, which consists of a nitrogenous base, a pentose sugar, and a phosphate group.
1. Monomer Structure: Nucleotides
- Nitrogenous Bases: The nitrogenous bases are divided into purines (adenine and guanine) and pyrimidines (cytosine, thymine in DNA, and uracil in RNA). The base pairing is crucial, where adenine pairs with thymine (or uracil in RNA) and cytosine pairs with guanine.
- Pentose Sugar: DNA contains deoxyribose, lacking an oxygen atom on the 2' carbon, making it more stable than RNA, which contains ribose with a hydroxyl group.
- Phosphate Group: Nucleotides contain one to three phosphate groups that connect the sugars via phosphodiester bonds, forming the sugar-phosphate backbone of nucleic acids with defined 5' and 3' ends.
2. Polynucleotide Structure
Polynucleotides are chains of nucleotides linked together. In DNA, two antiparallel strands form a double helix stabilized by hydrogen bonds between complementary bases. In RNA, the structure is typically single-stranded, but it can fold into complex shapes due to internal base pairing.
3. Functions of Nucleic Acids
- Genetic Information Storage: DNA encodes the genetic instructions necessary for the synthesis of proteins, regulating cellular processes.
- Genetic Information Transfer: Through transcription, DNA is converted into RNA, which is then translated into proteins, fundamental to the flow of genetic information within a cell.
- Types of RNA: Different forms of RNA play unique roles, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).
- Regulation and Catalysis: Some RNA molecules, such as ribozymes, perform catalytic functions, and others like miRNA and siRNA regulate gene expression.
Conclusion
Understanding the structure and function of nucleic acids is critical for comprehending genetic material's role in heredity, evolution, and biotechnology.
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Key Concepts
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Nucleotide: The individual unit making up nucleic acids, consisting of a base, sugar, and phosphate.
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DNA vs. RNA: DNA is double-stranded and stable, while RNA is single-stranded and more reactive.
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Phosphodiester Bonds: Connections between nucleotides forming the backbone of nucleic acids.
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Functions of Nucleic Acids: DNA stores genetic information; RNA plays roles in coding, decoding, regulation, and expression of genes.
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Mutations: Changes in DNA that contribute to genetic variation and evolution.
Examples & Applications
DNA consists of four nucleotide bases: adenine, thymine, cytosine, and guanine, where A pairs with T and C pairs with G.
RNA contains uracil instead of thymine, leading to different base pairing (A with U) in RNA molecules.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
Adenine pairs with T, in DNA that's how it be.
Stories
A cell's factory produces proteins, it needs workers: mRNA delivers the message, tRNA brings the right items, while rRNA builds with care.
Memory Tools
To remember nucleotide parts: 'B-S-P' for Base, Sugar, Phosphate.
Acronyms
TRAP for the flow of information
Transcription
RNA
Assembly
Protein.
Flash Cards
Glossary
- Nucleotide
The basic building block of nucleic acids, composed of a nitrogenous base, a sugar, and a phosphate group.
- DNA
Deoxyribonucleic acid, the molecule that carries genetic information in living organisms.
- RNA
Ribonucleic acid, a molecule that plays several roles in the expression of genes and can carry genetic information.
- Phosphodiester Bond
The covalent bond formed between the phosphate group of one nucleotide and the sugar of another.
- Base Pairing
The specific hydrogen bonding between nitrogenous bases of DNA (A-T and C-G) or RNA (A-U and C-G).
- mRNA
Messenger RNA, the form of RNA that carries genetic information from DNA to ribosomes for protein synthesis.
- tRNA
Transfer RNA, a type of RNA that transports amino acids to the ribosome during protein synthesis.
- rRNA
Ribosomal RNA, the RNA component of ribosomes essential for protein synthesis.
- Ribozyme
An RNA molecule that has the ability to catalyze biochemical reactions.
Reference links
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