The structure of ψ DNA

THE STRUCTURE OF DNA Our Genetic Makeup DNA is essential to life. It carries the genetic material of living organisms and provides cells with the necessary instructions for making the proteins they need to function. WHAT IS DNA? DNA, short for “deoxyribonucleic acid,” is a double-stranded macromolecule. Nucleic acids are complex organic materials found in cells. DNA contains the genetic instructions for development, function, growth, and reproduction of all living organisms and many viruses. Fun fact: DNA’s genetic instructions are passed down from parents to their offspring. HOW IS DNA REPRESENTED? Double helix Untwisted ladder DNA can be represented in two ways—either as a double helix (twisted ladder) or as an untwisted ladder. The rungs of the ladder are composed of pairs of nitrogenous bases (base pairs), and the sides of the ladder consist of alternating sugar molecules and phosphates. Nitrogenous bases Sugar molecule Phosphate WHAT MAKES UP YOUR DNA? DNA is composed of nucleotides; each consists of a nitrogenous base, a sugar molecule, and a phosphate. These nucleotide components are made up of carbon, oxygen, nitrogen, phosphorus, and hydrogen atoms. Fun fact: The phosphate makes strong bonds with the sugar, giving DNA a stable “backbone” that is referred to as the sugar-phosphate backbone. Fun fact: It takes about 10 nucleotides to make a complete twist. Phosphorus atoms Sugar Oxygen atoms Carbon atoms Nitrogen atoms Hydrogen atoms DNA PAIRINGS There are four potential nitrogenous bases: adenine, thymine, cytosine, and guanine. Two DNA strands are joined together by hydrogen bonds that bind these bases: adenine to thymine, and cytosine to guanine. This process is called base pairing. Adenine Thymine Cytosine Guanine Hydrogen bonds HOW DOES DNA FIT INTO A CELL? Histone In order for DNA to fit inside a cell’s nucleus, it must condense and compact. It does this by wrapping around a cluster of eight histone proteins two and a half times, forming a nucleosome. Consecutive nucleosomes are connected to one another by linker DNA, and they look like beads on a string. Nucleosome HOW DOES DNA FIT INTO A CELL? Chromosome The nucleosomes are then coiled and compacted into chromatin, which is a complex of DNA and protein. The chromatin continues to coil and supercoil until it forms a chromosome. Chromatin Steps of mRNA Gene Expression DNA Transcription Translation Proteins HOW DOES THE BODY BENEFIT FROM DNA? Gene expression is the process when DNA directs the production of functional products that are beneficial to the body. In transcription, DNA is used as a template to produce two different types of RNA (regulatory RNA or mRNA (messenger RNA)). Regulatory RNA stays in the nucleus but mRNA exits the nucleus to be translated for the production of protein (a chain of amino acids that are essential for the functioning of cells), in a process called translation. GENE EXPRESSION: TRANSCRIPTION Transcription is the process of transcribing DNA to produce RNA. It begins when a RNA polymerase opens the DNA, like the slider on a zipper. As the RNA polymerase continues down the length of the DNA it reads one strand of the DNA and transcribes the DNA information, creating an RNA transcript. The transcript is a complimentary copy of the DNA sequence. When the RNA transcript is complete, it separates from the DNA template. A regulatory RNA transcript stays in the nucleus while mRNA transcript exits the nucleus through a nuclear pore, where it enters the cytoplasm for part two of gene expression. RNA Transcript RNA polymerase GENE EXPRESSION: TRANSLATION Translation is the process of using the mRNA to produce proteins. It begins when a tRNA (transfer RNA) molecule binds itself to the mRNA start codon. Each tRNA molecule carries an amino acid. A ribosome is formed so the amino acids of tRNA are joined to build a protein. The amino acid of the tRNA in the first position is attached to the tRNA in the second position and then is released to allow room for a new tRNA. This pattern continues until the ribosome gets to a stop codon. The ribosome releases the protein from the tRNA, and the protein can be further modified in other cellular structures or directly used by the body. Amino acid mRNA Ribosome tRNA 1st position 2nd position WHICH CELLS HAVE DNA? Cells in animals, including humans, are responsible for carrying out the functions of each body system. These cells are eukaryotic, meaning they have a membrane-bound nucleus that contains most of their DNA, compacted into several chromosomes. WHICH CELLS HAVE DNA? Plant cells are responsible for carrying out the essential functions of plants, including photosynthesis and cellular respiration. Like animal cells, plant cells are considered eukaryotic. WHICH CELLS HAVE DNA? Unlike eukaryotic cells, prokaryotic cells do not have a membrane-bound nucleus. In prokaryotic cells, like bacterial cells, DNA is stored in the nucleoid region of the cytoplasm. Prokaryotic cells Bacterial cells View a 3D Tour of all the images featured in this eBook! To launch the Tour in Visible Biology: 1. Copy this link: https://apps.visiblebody.com/share/?p=&t=4_63950_637679985924940000_324691 2. Use the share link button in the app. 3. Paste the link to view the tour. A universe of biological visuals and reference texts at your fingertips! www.visiblebody.com