Three components comprise each nucleotide: a nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group ( Figure 3.31). The nucleotides combine with each other to form a polynucleotide, DNA or RNA. Other types of RNA-like rRNA, tRNA, and microRNA-are involved in protein synthesis and its regulation.ĭNA and RNA are comprised of monomers that scientists call nucleotides. This intermediary is the messenger RNA (mRNA). The DNA molecules never leave the nucleus but instead use an intermediary to communicate with the rest of the cell. The other type of nucleic acid, RNA, is mostly involved in protein synthesis. DNA controls all of the cellular activities by turning the genes “on” or “off.” Many genes contain the information to make protein products. A chromosome may contain tens of thousands of genes. In eukaryotic cells but not in prokaryotes, DNA forms a complex with histone proteins to form chromatin, the substance of eukaryotic chromosomes. The cell's entire genetic content is its genome, and the study of genomes is genomics. In prokaryotes, the DNA is not enclosed in a membranous envelope. It is in the nucleus of eukaryotes and in the organelles, chloroplasts, and mitochondria. DNA is the genetic material in all living organisms, ranging from single-celled bacteria to multicellular mammals. The two main types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). They carry the cell's genetic blueprint and carry instructions for its functioning. Nucleic acids are the most important macromolecules for the continuity of life. Describe nucleic acids' structure and define the two types of nucleic acids.This is critical when cells divide because each new cell needs to have an exact copy of the DNA present in the old cell.By the end of this section, you will be able to do the following: Each strand of DNA in the double helix can serve as a pattern for duplicating the sequence of bases. The structure of the double helix is somewhat like a ladder, with the base pairs forming the ladder’s rungs and the sugar and phosphate molecules forming the vertical sidepieces of the ladder.Īn important property of DNA is that it can replicate, or make copies of itself. Nucleotides are arranged in two long strands that form a spiral called a double helix. ![]() ![]() Together, a base, sugar, and phosphate are called a nucleotide. Each base is also attached to a sugar molecule and a phosphate molecule. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.ĭNA bases pair up with each other, A with T and C with G, to form units called base pairs. Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Mitochondria are structures within cells that convert the energy from food into a form that cells can use. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA). Nearly every cell in a person’s body has the same DNA. DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms.
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