DNA deoxyribonucleic acid is one of the most important molecules in your body, and though around Visible Biology is a visual guide to important biological concepts and processes, including DNA and chromosomes , prokaryotic vs. Visible Biology is now available for instructor demos and trials.
Did you know that in the average human cell, there is about 2m 6ft of DNA? How is all that genetic material packed into a space way smaller than the head of a pin? The short answer is a whole lot of twisting and winding.
DNA wraps around protein clusters called histones to form units called nucleosomes. These nucleosomes fold into a zig-zag patterned fiber, which then forms loops.
DNA structure and storage. Image from Visible Biology. There are 46 separate strings of DNA in each somatic cell of the human body. Each one of these is called a chromosome. Scientists group them into 23 homologous pairs, which means that the chromosomes in each pair are similar in structure and function.
The only exception to this is the 23rd pair—the sex chromosomes—in biologically male individuals. X and Y sex chromosomes only have certain regions autosomal regions that are homologous. Screenshot from animation in Visible Biology. The sides of this twisted ladder are composed of alternating molecules of sugar deoxyribose, to be precise and a phosphate group.
Molecular structure of DNA. Four nitrogenous bases—cytosine, thymine, adenine, and guanine—can be found on strands of DNA. In terms of their chemical structure, cytosine and thymine are pyrimidines and adenine and guanine are purines.
Adenine and thymine A and T always pair together, and guanine and cytosine G and C always pair together. They pair this way because A and T form two hydrogen bonds with each other and G and C form three. At the most basic level, different sections of DNA strands sequences of nitrogenous bases provide instructions for the synthesis of proteins.
A single section of DNA can even code for multiple proteins! Want to know something neat? Before we discuss transcription and translation, the two processes key to protein synthesis, we need to talk about another kind of molecule: RNA. They remove segments called introns and then splice the remaining segments, called exons, together. You can think of introns like padding between the exons. Also, remember how I mentioned that a single sequence of DNA can code for multiple proteins? Alternative splicing is the reason why: before the m RNA leaves the nucleus, its exons can be spliced together in different ways.
If you have any other comments or suggestions, please let us know at comment yourgenome. Can you spare minutes to tell us what you think of this website?
Open survey. In: Facts In the Cell. This is carried out by an enzyme called helicase which breaks the hydrogen bonds holding the complementary bases of DNA together A with T, C with G.
The two separated strands will act as templates for making the new strands of DNA. As a result of their different orientations, the two strands are replicated differently: An illustration to show replication of the leading and lagging strands of DNA.
Related Content:. What is a genome? What is DNA? What is a cell? How helpful was this page? What's the main reason for your rating?
0コメント