DNA function & structure (with diagram) (article) | Khan Academy
Nucleic acid structure refers to the structure of nucleic acids such as DNA and RNA. Chemically 5-carbon sugar which is called deoxyribose (found in DNA) and ribose Purines consist of a double ring structure, a six membered and a five The sugar pucker occurs at the C3'-endo and in RNA 2'-OH inhibits C2'- endo. Deoxyribonucleic acid is a molecule composed of two chains that coil around each other to . The sugar in DNA is 2-deoxyribose, which is a pentose (five- carbon) sugar. all the adenosine bases within its genome replaced by 2,6- diaminopurine. .. The relationship between the nucleotide sequences of genes and the. Phosphodiester bonds in DNA polymers connect the 5' carbon of one nucleotide to In a double helix structure, the strands of DNA run antiparallel, meaning the 5' end of one DNA strand is parallel . DNA repair 2 .. 21/35 + 9/35=30/35=6/7 Factoring the difference of perfect squares is just how you happen to solve it.
For example, UV light can damage DNA by producing thymine dimerswhich are cross-links between pyrimidine bases. Because of inherent limits in the DNA repair mechanisms, if humans lived long enough, they would all eventually develop cancer. Although most of these damages are repaired, in any cell some DNA damage may remain despite the action of repair processes.
These remaining DNA damages accumulate with age in mammalian postmitotic tissues. This accumulation appears to be an important underlying cause of aging. Most intercalators are aromatic and planar molecules; examples include ethidium bromideacridinesdaunomycinand doxorubicin. For an intercalator to fit between base pairs, the bases must separate, distorting the DNA strands by unwinding of the double helix.
This inhibits both transcription and DNA replication, causing toxicity and mutations.
The set of chromosomes in a cell makes up its genome ; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes. Transmission of genetic information in genes is achieved via complementary base pairing.
Usually, this RNA copy is then used to make a matching protein sequence in a process called translationwhich depends on the same interaction between RNA nucleotides. In alternative fashion, a cell may simply copy its genetic information in a process called DNA replication. The details of these functions are covered in other articles; here the focus is on the interactions between DNA and other molecules that mediate the function of the genome.
Genes and genomes Further information: In eukaryotes, DNA is located in the cell nucleuswith small amounts in mitochondria and chloroplasts.
In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the nucleoid. A gene is a unit of heredity and is a region of DNA that influences a particular characteristic in an organism.DNA, Chromosomes, Genes, and Traits: An Intro to Heredity
Although the two strands are aligned by hydrogen bonds in base pairs, the stronger forces holding the two strands together are stacking interactions between the bases. These stacking interactions are stabilized by Van der Waals forces and hydrophobic interactions, and show a large amount of local structural variability. The secondary structure of RNA consists of a single polynucleotide. Both single- and double-stranded regions are often found in RNA molecules.
The antiparallel strands form a helical shape. Stem-loop or hairpin loop is the most common element of RNA secondary structure. Bulges and internal loops are formed by separation of the double helical tract on either one strand bulge or on both strands internal loops by unpaired nucleotides. A tetraloop is a four-base pairs hairpin RNA structure.
There are three common families of tetraloop in ribosomal RNA: UNCG is the most stable tetraloop. H-type fold pseudoknots are best characterized. In H-type fold, nucleotides in the hairpin loop pairs with the bases outside the hairpin stem forming second stem and loop.
Diagram showing how the two strands of double stranded DNA runs anti-parallel to each other. One strand runs in a 3' to 5' direction while the other runs in a 5' to 3' direction. The nucleotides forming each DNA strand are connected by noncovalent bonds, called hydrogen bonds.
DNA - Wikipedia
Considered individually, hydrogen bonds are much weaker than a single covalent bond, such as a phosphodiester bond.
But, there are so many of them that the two DNA polymers are very strongly connected to each other. The hydrogen bonds that join DNA polymers happen between certain hydrogen atoms on one base called hydrogen bond donors and certain oxygen or nitrogen atoms on the base across from it called hydrogen bond acceptors.
The A nucleotides are always hydrogen bonded to T nucleotides, and C nucleotides are always hydrogen bonded to G nucleotides. This selective binding is called complementary base pairing, and creates consistency in the nucleotide sequences of the two DNA polymers that join together to make a chromosome.
This was first observed by Erwin Chargaff, who developed methods for counting nucleotides in DNA samples, and found that the percent of A nucleotides always equaled the percent of T nucleotides, and the percent of G nucleotides always equaled the percent of C nucleotides within a margin of error.
Nucleic acid structure
Now, we know that complementary base pairing can be explained by reference to hydrogen bonding between the donors and acceptors on the bases of each nucleotide: A nucleotides and T nucleotides have a match one donor and one acceptor eachand C nucleotides and G nucleotides have a match the former has one donor and two acceptors, while the latter has one acceptor and two donors.
Diagram showing how adenine and thymine base pair while guanine and cytosine base pair. Adenine and thymine are bound to one another via two hydrogen bonds while guanine and cytosine are bound to one another via three hydrogen bonds.
The Biological function of DNA DNA polymers direct the production of other polymers called proteins A protein is one or more polymers of monomers called amino acids. Proteins are the workhorse molecules in your cells. They act as enzymes, structural support, hormones, and a whole host of other functional molecules. All traits derive from the interactions of proteins with each other and the surrounding environments.
A chromosome consists of smaller segments called genes Chromosomes are very long structures consisting of two DNA polymers, joined together by hydrogen bonds connecting complementary base pairs.
A chromosome is divided into segments of double-stranded DNA called genes. Image showing how a chromosome is made up of DNA which contains genes. Each gene is further divided into three nucleotide subsegments called codons A codon is a segment or piece of double stranded DNA that is three nucleotides long. A gene can be thought of as many three-nucleotide codons strung together.
DNA vs. RNA – 5 Key Differences and Comparison | Technology Networks
Image showing how each gene is made up codons aka the A, T, G, and C bases. Understanding DNA structure and function Earlier, we compared a DNA polymer to a sentence, and the nucleotide monomers that make up a polymer to the letters of the alphabet that are used to write sentences down. Now that we know what genes are, and what codons are, we can extend this analogy a bit further, and begin to get an insight into how DNA stores biological information. If nucleotides are like letters, then codons are like words.
Just like in English, where each word is associated with a dictionary definition, the codons of the DNA language are each associated with specific amino acids.