https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/dna-and-rna-structure/v/dna-deoxyribonucleic-acid 2023-06-06T10:35:22.92767095Z DNA DNA, or deoxyribonucleic acid, is the molecular basis for inheritance, discovered in the mid-1800s and understood in 1953 with the double helix structure. Composed of a sugar-phosphate backbone and base pairs (adenine-thymine, guanine-cytosine), DNA stores genetic information, replicates, and expresses traits. The human genome contains 6 billion base pairs across 46 chromosomes, making it a compact and efficient information storage system. Sal Khan video https://cdn.kastatic.org/googleusercontent/N-FD1seHs-vdXACc6Ug4MuC44TkW3_s9SQcxTbnTpvAsX9wVNZXctud872V8KvhGq_fRRDQjDIVNX55fJrm1WiMGGw DNA DNA, or deoxyribonucleic acid, is the molecular basis for inheritance, discovered in the mid-1800s and understood in 1953 with the double helix structure. Composed of a sugar-phosphate backbone and base pairs (adenine-thymine, guanine-cytosine), DNA stores genetic information, replicates, and expresses traits. The human genome contains 6 billion base pairs across 46 chromosomes, making it a compact and efficient information storage system. https://cdn.kastatic.org/ka-youtube-converted/AmOO4j0E408.mp4/AmOO4j0E408.mp4 782 DNA https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/dna-and-rna-structure/v/molecular-structure-of-dna 2023-12-04T19:02:25.924542584Z Molecular structure of DNA DNA, short for deoxyribonucleic acid, consists of nucleotides forming a double helix structure. Nucleotides contain a phosphate group, deoxyribose sugar, and a nitrogenous base. The bases, adenine, thymine, cytosine, and guanine, pair up through hydrogen bonds, creating the rungs of the DNA ladder. Sal Khan video https://cdn.kastatic.org/googleusercontent/8CAJsW9lm5PD2iqAOUcaBs0SdH5kHWd9vp0hQQZSfvR0266sVqQL_LcDa7DaTO9bZfE8uC8NPZkcrCvMSBiwdedR Molecular structure of DNA DNA, short for deoxyribonucleic acid, consists of nucleotides forming a double helix structure. Nucleotides contain a phosphate group, deoxyribose sugar, and a nitrogenous base. The bases, adenine, thymine, cytosine, and guanine, pair up through hydrogen bonds, creating the rungs of the DNA ladder. https://cdn.kastatic.org/ka-youtube-converted/L677-Fl0joY.mp4/L677-Fl0joY.mp4 781 DNA https://www.khanacademy.org/science/ap-biology/chemistry-of-life/nucleic-acids-ap/v/antiparallel-structure-of-dna-strands 2023-12-04T19:02:25.924542584Z Antiparallel structure of DNA strands DNA structure consists of two strands, each with a backbone of alternating phosphate and sugar groups. These strands are linked by complementary nitrogenous bases, forming a ladder-like structure. The strands are antiparallel, meaning they run in opposite directions, which is crucial for DNA replication. Sal Khan video https://cdn.kastatic.org/googleusercontent/jlVOYhrBGzFF4uavk6HLPEFezcJ4JuLlY5qyQV1xEBLQZkR_bUVOk-7iIDFFKzmKmfe1iWYRUsI8ZF4LX2aIjL_r Antiparallel structure of DNA strands DNA structure consists of two strands, each with a backbone of alternating phosphate and sugar groups. These strands are linked by complementary nitrogenous bases, forming a ladder-like structure. The strands are antiparallel, meaning they run in opposite directions, which is crucial for DNA replication. https://cdn.kastatic.org/ka-youtube-converted/0CQ5ls3Uc2Q.mp4/0CQ5ls3Uc2Q.mp4 597 DNA https://www.khanacademy.org/science/ms-biology/x0c5bb03129646fd6:inheritance-and-variation/x0c5bb03129646fd6:genes-proteins-and-traits/v/genes-proteins-and-traits 2024-05-09T17:42:08.599818576Z Genes, proteins, and traits Genes are specific stretches of nucleotides on a DNA molecule. Genes encode proteins, which are made up of amino acids. The order of nucleotides in a gene determines the order of amino acids in a protein. A protein’s amino acids determine its 3D shape and its functions in the cell, which, in turn, affect an organism’s traits. Khan Academy video https://cdn.kastatic.org/ka_thumbnails_cache/13c2afcc-cd5f-45ff-90f2-08e3c4600c8f_1280_720_base.png Genes, proteins, and traits Genes are specific stretches of nucleotides on a DNA molecule. Genes encode proteins, which are made up of amino acids. The order of nucleotides in a gene determines the order of amino acids in a protein. A protein’s amino acids determine its 3D shape and its functions in the cell, which, in turn, affect an organism’s traits. https://cdn.kastatic.org/ka-youtube-converted/tfZfLDRu39c.mp4/tfZfLDRu39c.mp4 293 DNA https://www.khanacademy.org/science/ap-biology/chemistry-of-life/properties-structure-and-function-of-biological-macromolecules/v/overview-of-protein-structure 2021-03-18T10:33:22Z Overview of protein structure Primary, secondary, tertiary and quaternary protein structure. Beta pleated sheets and alpha helices. video https://cdn.kastatic.org/googleusercontent/UbkThjoOiDiecZh69T1rBXQPNKHCs6-M6Ypbkwo3sGFGT56yYDBRb3ATwL9MIYIDZF7em5M91F7kd0IG6e_Pc8SQDg Overview of protein structure Primary, secondary, tertiary and quaternary protein structure. Beta pleated sheets and alpha helices. https://cdn.kastatic.org/ka-youtube-converted/MODnIkQvyz0.mp4/MODnIkQvyz0.mp4 598 DNA https://www.khanacademy.org/science/cambridge-o-level-biology-cie/x2a084a90105205d2:inheritance/x2a084a90105205d2:dna/a/levels-of-dna-organization 2024-12-19T15:28:16.523849485Z Levels of DNA organization This article reviews the different levels of DNA organization, from DNA strands to chromosomes. article https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/dna-and-rna-structure/a/nucleic-acids 2026-03-17T04:40:31.334379942Z Nucleic acids DNA and RNA structure and function. Nucleotides and polynucleotides. mRNA, rRNA, tRNA, miRNA, and siRNA. article https://www.khanacademy.org/science/ms-biology/x0c5bb03129646fd6:inheritance-and-variation/x0c5bb03129646fd6:genes-proteins-and-traits/a/genes-proteins-and-traits-ms 2026-02-27T17:50:36.702607024Z Genes, proteins, and traits Learn about how genes encode proteins, which in turn affect an organism's traits. article https://www.khanacademy.org/science/cambridge-o-level-biology-cie/x2a084a90105205d2:inheritance/x2a084a90105205d2:dna/a/dna-structure-and-function 2021-05-25T21:59:58Z DNA structure and function article https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/translation/a/intro-to-gene-expression-central-dogma 2021-04-29T08:00:32Z Intro to gene expression (central dogma) How genes in DNA can provide instructions for proteins. The central dogma of molecular biology: DNA → RNA → protein. article https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/regulation-of-gene-expression-and-cell-specialization/a/overview-of-eukaryotic-gene-regulation 2021-04-29T07:54:00Z Overview: Eukaryotic gene regulation How different genes are expressed in different cell types. The big picture of eukaryotic gene regulation. article https://www.khanacademy.org/science/ms-biology/x0c5bb03129646fd6:inheritance-and-variation/x0c5bb03129646fd6:genes-proteins-and-traits/e/understand-genes-proteins-and-traits 2025-07-01T21:05:20.470958635Z Understand: genes, proteins, and traits Check your understanding of genes, proteins, and traits in this set of free, standards-aligned practice questions. Khan Academy exercise https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/dna-and-rna-structure/e/dna-and-rna-structure 2025-11-24T21:00:40.80360556Z DNA and RNA structure Test your knowledge of DNA and RNA structure! Megan Cohn exercise