Table of Contents
- The genetic code in cells is made up of DNA.
- DNA specifies the construction of proteins and the generation of RNA.
- DNA and RNA are nucleotide polymers.
Structure of nucleic acids
- Nucleic acids are information molecules in cells.
- Deoxyribonucleic acid is the most famous nucleic acid.
- Ribonucleic acid is less known and very important in cells.
- Nucleic acid polymers are made up of repeating nucleotide monomers.
- The structure of nucleic acid is complex because of the following reasons:
- The nucleic acid monomers are nucleotides. Nucleotides contain 3 components which makes them complicated before the formation of chains.
- Nucleic acids can be double-stranded or single-stranded. Joining nucleotides together leads to the formation of polynucleotide chains.
- RNA has a single polynucleotide chain while DNA has two double -helix polynucleotide chains.
- Nucleotides are built from 3 components;
- Pentose sugar (5 carbon) – DNA has deoxyribose sugar while RNA has a ribose sugar
- Nitrogenous base – It is a double ring structure or a single ring structure containing many nitrogen atoms
- Phosphate group – Contains a phosphorus atom that is surrounded by atoms of oxygen. They have a negative charge which makes nucleic acids negative in charge.
- Carbon atoms on nucleotides are numbered using the following system:
- The sugar carbon atoms are numbered in a sequence from one to five.
- The numbered carbon atoms are awarded a prime designation resulting in 1′, 2′, 3′,4′ and 5′.
- Oneprime carbon is the first carbon.
- All other carbon atoms are numbered consecutively.
The naming of nucleotide bases
- There are five nitrogenous bases found on nucleotides. This includes the following:
- Adenine (A)
- Guanine (G)
- Cytosine (C)
- Thymine (T)
- Nucleotides vary depending on the nitrogenous base attached to it.
- Nitrogenous bases fall into two categories:
- Pyrimidine- Contain a single ring structure and two nitrogen atoms.
- Purines- contain 2 fused rings with each ring containing two nitrogen atoms.
DNA and RNA synthesis
- Nucleotides are joined together by a condensation reaction.
- Repeating the process leads to the formation of a polynucleotide.
- A primary structure is formed by the type and number of nucleotides.
Differences between RNA and DNA
- DNA has thymine nitrogenous base while RNA has uracil base.
- DNA nucleotides have a deoxyribose sugar while RNA nucleotides have a ribose sugar.
- RNA is single-stranded while DNA is double-stranded.
The DNA double helix
- The DNA secondary structure is a double helix.
- Two chains of polynucleotides join to form a molecule with a twisted ladder-like shape.
- The sides of the ladder represent the Sugar phosphate backbones.
- Nitrogenous bases project from the sugar backbone.
- The two double helix chains are antiparallel.
- The antiparallel strands are joined by hydrogen bonds between bases.
- Adenine (A) joins to Thymine (T) by hydrogen bonds.
- Cytosine (C) joins Guanine (G) by hydrogen bonds.
The function of DNA and RNA
- Protein structure; the structure of proteins is determined by the DNA nucleotide sequence. Protein is generated from the process of transcription and translation.
- RNA structure; the structure of RNA id determined by the DNA nucleotide sequence. The process of transcription generates nucleotides required to build RNA.
- DNA regulation; it happens through the interaction of DNA binding proteins with special DNA regulatory sequences.
Types of RNA and their function
- Messenger RNA (mRNA) carries a protein structure code from DNA to ribosomes where proteins are generated.
- Transfer RNA (tRNA) decodes the mRNA message by allocating an amino acid that matches to the mRNA code.
- Ribosomal RNA (rRNA) is part of the structure of the ribosome.
|Structure of RNA||Single strand of nucleotides, ribose sugar, uracil (instead of thymine)|
|Adenine pairs with…||Uracil|
|Uracil pairs with…||Adenine|
|Guanine pairs with…||Cytosine|
|Cytosine pairs with…||Guanine|
|Function of mRNA||Carries genetic information from DNA in the nucleus to the cytosol in eukaryotic cells|
|Structure of mRNA||Single uncoiled chain|
|Function of tRNA||Amino acids bind to it and it carries the amino acid to the ribosome for protein synthesis|
|Shape of tRNA||Single chain (about 80 nucleotides) in hairpin shape|
|Number of tRNA varieties||45|
|Most abundant form of RNA||rRNA|
|Function of rRNA||Site of protein synthesis|
|Structure of rRNA||Globular shape composed of rRNA and proteins|
|Transcription||Transfer of genetic information from DNA to RNA|
|Location of transcription||In the nucleus|
|DNA separation||At the beginning of the gene|
|Enzyme used in transcription||RNA Polymerase|
|Role of RNA Polymerase in transcription||Binds to promoter region and causes DNA to separate|
|Promoter Region||Nucleotide sequence at the beginning of a gene, shows RNA Polymerase where to bind|
|TATA Box||Series of Thymine and Adenine on the DNA template|
|Template strands used in transcription||One strand of DNA|
|Termination Signal||Specific sequence of nucleotides on the DNA template that signals the end of transcription|
|Transcription stop||When RNA Polymerase hits the termination signal|
|RNA Polymerase action at termination signal||Breaks off from the DNA template and the mRNA|
|Reusability of DNA template||Yes, it can be reused to make more mRNA|
|Product of transcription||mRNA (called transcript)|
|Destination of mRNA after transcription||Out of the nucleus (through nuclear pores) and into the cytosol where it binds to a ribosome|
|Codon||Every 3 mRNA nucleotides|
|Codon’s function||Codes for a particular amino acid|
|Determinant of amino acid sequence in the protein||mRNA|
|Number of codons||64|
|AUG||Codon that signals the ribosome to start translation of mRNA|
|AUG codes for||Methionine|
|Stop codons||UAA, UAG, and UGA|
|Translation||Process of assembling polypeptides from the coded message of mRNA|
|Requirements for translation||Ribosome and tRNA|
|Ribosome’s role in translation||Holds mRNA in place|
|tRNA’s role in translation||Transports amino acids to mRNA|
|Composition of a ribosome||rRNA and proteins|
|Number of binding sites on a ribosome||Three|
|Function of the first binding site||Holds mRNA transcript in place|
|Function of the second and third binding sites||Allow tRNA to bind to them|
|tRNA composition||A region where the amino acid binds and the opposite side contains an anticodon|
|Anticodon||The complement of a codon triplet on mRNA|
|Start of polypeptide assembly||Ribosome attaches to the start codon (AUG)|
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|What are nucleic acids made up of?||Nucleotides|
|What is the function of nucleic acids?||Carry genetic information and instructions for cell functioning|
|What are the two main types of nucleic acids?||DNA and RNA|
|Where is DNA found in eukaryotes?||Nucleus, chloroplasts, and mitochondria|
|Is DNA enclosed in a nucleus in prokaryotes?||No|
|What is the entire genetic content of a cell called?||Genome|
|What forms eukaryotic chromosomes?||DNA and histone proteins (chromatin)|
|What is the function of DNA?||Control cellular activities by turning genes “on” or “off”|
|What is the function of RNA?||Involved in protein synthesis and regulation|
|What are the nitrogenous bases in DNA?||Adenine (A), guanine (G), cytosine (C), and thymine (T)|
|What are the nitrogenous bases in RNA?||Adenine (A), guanine (G), cytosine (C), and uracil (U)|
|What is the sugar in RNA?||Ribose|
|What is the sugar in DNA?||Deoxyribose|
|What are the three components of a nucleotide?||Nitrogenous base, pentose sugar, and phosphate group|
|What type of bonds link nucleotides in a nucleic acid?||Phosphodiester linkages|
|What type of bonding holds the two strands of DNA together?||Hydrogen bonds|
|What is the rule for base pairing in DNA?||A can only pair with T, and G can only pair with C|
|How is DNA able to replicate?||Complementary strands allow for each strand to serve as a template for the synthesis of a new strand|
|How is DNA compacted in prokaryotes?||Supercoiling|
|How is DNA compacted in eukaryotes?||Wrapping around histones to form nucleosomes and further compaction into 30 nm fibers|
|What are the two regions of eukaryotic chromosomes in interphase?||Heterochromatin and euchromatin|
|What are the four major types of RNA?||mRNA, rRNA, tRNA, and miRNA|
|What is the function of mRNA?||Carries genetic code from DNA and serves as a template for protein synthesis|
|What is the function of rRNA?||Major component of ribosomes for protein synthesis|
|What is the function of tRNA?||Carries correct amino acids to the site of protein synthesis|
|What is the function of miRNA?||Regulates gene expression|
|What is the Central Dogma of Molecular Biology?||DNA transcribed into mRNA, which is then translated into protein|
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Editorial Team. (2023, May 29). DNA and RNA: Instructions for Life. Help Write An Essay. Retrieved from https://www.helpwriteanessay.com/blog/dna-and-rna-instructions-for-life/