https://www.khanacademy.org/science/shs-biology-2/x2ea931c66bba6acd:3rd-quarter/x2ea931c66bba6acd:lesson-3-genetics-central-dogma/e/the-genetic-code-in 2025-03-15T08:00:32.570165204Z The Genetic Code This exercise tests knowledge on interpreting the genetic code, translation and mutations. Nivedhitha exercise https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/translation/a/the-genetic-code-discovery-and-properties 2021-04-29T07:51:49Z The genetic code The genetic code links groups of nucleotides in an mRNA to amino acids in a protein. Start codons, stop codons, reading frame. article https://www.khanacademy.org/science/hs-bio/x230b3ff252126bb6:gene-expression-and-regulation/x230b3ff252126bb6:untitled-348/a/the-genetic-code 2024-09-19T18:52:37.568743011Z The genetic code Learn about how the information in an mRNA sequence is decoded to make a polypeptide. article https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/dna-and-rna-structure/v/molecular-structure-of-rna 2023-06-22T09:32:02.370557018Z Molecular structure of RNA DNA and RNA have different sugar backbones: deoxyribose for DNA and ribose for RNA. Notably, RNA has uracil instead of thymine as a nitrogenous base. RNA plays various roles in cells, including messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA), and microRNA, and it is a vital part of processes such as transcription, translation, and cellular functions. Sal Khan video https://cdn.kastatic.org/googleusercontent/h1FObigLo5Ws6DQyI0rvscZJD8U2s8Ob78wh75lDvw2DSbV8myer4FbWdbzDvRKmeRTN7Wv_zWj0s6SYj0S4COM Molecular structure of RNA DNA and RNA have different sugar backbones: deoxyribose for DNA and ribose for RNA. Notably, RNA has uracil instead of thymine as a nitrogenous base. RNA plays various roles in cells, including messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA), and microRNA, and it is a vital part of processes such as transcription, translation, and cellular functions. https://cdn.kastatic.org/ka-youtube-converted/jUUJSOM1ihU.mp4/jUUJSOM1ihU.mp4 690 Protein synthesis and gene expression https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/transcription-and-rna-processing/a/overview-of-transcription 2021-04-29T07:53:54Z Overview of transcription In transcription, the DNA sequence of a gene is transcribed (copied out) to make an RNA molecule. article https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/transcription-and-rna-processing/v/transcription-and-mrna-processing 2025-07-21T19:27:31.703149266Z Transcription and mRNA processing Transcription involves rewriting genetic information from DNA to mRNA, with RNA polymerase playing a crucial role. In eukaryotic cells, DNA to mRNA transcription occurs within the nucleus, producing pre-mRNA. This pre-mRNA undergoes processing, including the addition of a 5' cap, a poly-A tail, and splicing out introns, resulting in mature mRNA, which then leaves the nucleus for protein translation. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/7478f5d7-806e-42fe-99a1-eaa2d48c4e72_1280_720_base.png Transcription and mRNA processing Transcription involves rewriting genetic information from DNA to mRNA, with RNA polymerase playing a crucial role. In eukaryotic cells, DNA to mRNA transcription occurs within the nucleus, producing pre-mRNA. This pre-mRNA undergoes processing, including the addition of a 5' cap, a poly-A tail, and splicing out introns, resulting in mature mRNA, which then leaves the nucleus for protein translation. https://cdn.kastatic.org/ka-youtube-converted/JQIwwJqF5D0.mp4/JQIwwJqF5D0.mp4 625 Protein synthesis and gene expression https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/transcription-and-rna-processing/v/post-translational-regulation 2023-06-22T09:32:02.370557018Z Post-transcriptional regulation Post-transcriptional regulation occurs in eukaryotes, stabilizing mRNA for translation. DNA transcribes into RNA, with exons coding for proteins and introns removed by spliceosomes. The mRNA acquires a 5' prime cap and 3' prime poly-A tail for protection and translation promotion. RNA editing, a rare process, alters RNA sequences through insertion, deletion, or base substitution, impacting viral enzymes and functions. Tracy Kim Kovach video https://cdn.kastatic.org/googleusercontent/KuRP_XvqqIhCysA4ilj4EXReqtZcRCPwG07CaSCcBngg89xAV1MuBvIW6rhI_a14APuZI_Qr6dMkAymDBwbdzwxy Post-transcriptional regulation Post-transcriptional regulation occurs in eukaryotes, stabilizing mRNA for translation. DNA transcribes into RNA, with exons coding for proteins and introns removed by spliceosomes. The mRNA acquires a 5' prime cap and 3' prime poly-A tail for protection and translation promotion. RNA editing, a rare process, alters RNA sequences through insertion, deletion, or base substitution, impacting viral enzymes and functions. https://cdn.kastatic.org/ka-youtube-converted/nz5rbvt64kE.mp4/nz5rbvt64kE.mp4 368 Protein synthesis and gene expression https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/transcription-and-rna-processing/e/transcription-and-rna-processing 2025-11-24T22:40:49.011599776Z Transcription and RNA processing Test your knowledge of transcription and RNA processing! Megan Cohn exercise https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/transcription-and-rna-processing/a/eukaryotic-gene-transcription-going-from-dna-to-mrna 2026-01-28T06:40:40.514834287Z Eukaryotic gene transcription: Going from DNA to mRNA article https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/transcription-and-rna-processing/a/eukaryotic-pre-mrna-processing 2023-08-07T17:09:37.131449861Z Eukaryotic pre-mRNA processing 5' cap and poly-A tail. Splicing, introns, and exons. article https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/translation/v/translation-mrna-to-protein 2023-06-22T09:32:02.370557018Z Translation (mRNA to protein) Translation is the process whereby mRNA is converted into proteins by ribosomes. Translation occurs in ribosomes, which are cellular structures made of proteins and ribosomal RNA (rRNA). Here, mRNA is converted into amino acid sequences, forming polypeptides. Transfer RNA (tRNA) carries amino acids and matches them with mRNA codons, allowing ribosomes to synthesize proteins. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/52ee4b49-59a9-4d1f-810a-73cbf759856c_1280_720_base.png Translation (mRNA to protein) Translation is the process whereby mRNA is converted into proteins by ribosomes. Translation occurs in ribosomes, which are cellular structures made of proteins and ribosomal RNA (rRNA). Here, mRNA is converted into amino acid sequences, forming polypeptides. Transfer RNA (tRNA) carries amino acids and matches them with mRNA codons, allowing ribosomes to synthesize proteins. https://cdn.kastatic.org/ka-youtube-converted/ocAAkB32Hqs.mp4/ocAAkB32Hqs.mp4 850 Protein synthesis and gene expression https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/translation/e/translation-exercise 2025-11-24T22:40:49.011599776Z Translation Test your knowledge of translation! Haider Ali Bhatti exercise 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/translation/a/translation-overview 2021-04-29T08:03:37Z Overview of translation How the nucleotide sequence of an mRNA is translated into the amino acid sequence of a polypeptide (protein). article https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/translation/v/differences-in-translation-between-prokaryotes-and-eukaryotes 2023-06-22T15:57:36.106541556Z Differences in translation between prokaryotes and eukaryotes The process of mRNA translation differs between prokaryotes and eukaryotes. Prokaryotic mRNA has a Shine-Dalgarno sequence for ribosome binding, while eukaryotic mRNA has a 5' cap and poly-A tail for protection and ribosome binding. The first amino acid also differs: formylmethionine in prokaryotes and methionine in eukaryotes. Efrat Bruck video https://cdn.kastatic.org/googleusercontent/AxCUMyF5nZrUBy3AFXZ779jd5bmgg9P1CPpDkRGu08po9nrfFNyLkAObaJasqEKMThAlkOn9NnbdfrYgu4r1okVv Differences in translation between prokaryotes and eukaryotes The process of mRNA translation differs between prokaryotes and eukaryotes. Prokaryotic mRNA has a Shine-Dalgarno sequence for ribosome binding, while eukaryotic mRNA has a 5' cap and poly-A tail for protection and ribosome binding. The first amino acid also differs: formylmethionine in prokaryotes and methionine in eukaryotes. https://cdn.kastatic.org/ka-youtube-converted/WNZf4ip_R9s.mp4/WNZf4ip_R9s.mp4 396 Protein synthesis and gene expression https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/regulation-of-gene-expression-and-cell-specialization/e/regulation-of-gene-expression-and-cell-specialization 2023-08-16T05:06:02.353911136Z Regulation of gene expression and cell specialization Test your knowledge of regulation of gene expression and cell specialization! Megan Cohn exercise 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/ap-biology/gene-expression-and-regulation/regulation-of-gene-expression-and-cell-specialization/a/overview-gene-regulation-in-bacteria 2021-04-29T07:51:29Z Overview: Gene regulation in bacteria Overview of operons, regulatory DNA sequences, & regulatory genes. Repressor & activator proteins. article https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/regulation-of-gene-expression-and-cell-specialization/a/eukaryotic-transcription-factors 2023-08-07T17:09:37.131449861Z Transcription factors General and specific transcription factors. Transcription initiation complex & looping. Combinatorial regulation. article https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/regulation-of-gene-expression-and-cell-specialization/v/regulation-of-transcription 2023-06-22T15:57:36.106541556Z Regulation of transcription Gene regulation controls cell functions by determining which genes are transcribed. This process involves transcription factors, activators, enhancers, repressors, and silencers. Prokaryotes rely on gene regulation for environmental adaptation, while eukaryotes have more complex interactions and a nuclear envelope for added control. Understanding gene expression is crucial for studying cellular processes and responses. Tracy Kim Kovach video https://cdn.kastatic.org/googleusercontent/f3CU1AVUdwrg_9oHES4LZXev-LNEG8bb84JUIAAgeYFEwRJzIMdgj2rhcZ5xlqU4vz3sJHECOu3o8-srvpXonXQ Regulation of transcription Gene regulation controls cell functions by determining which genes are transcribed. This process involves transcription factors, activators, enhancers, repressors, and silencers. Prokaryotes rely on gene regulation for environmental adaptation, while eukaryotes have more complex interactions and a nuclear envelope for added control. Understanding gene expression is crucial for studying cellular processes and responses. https://cdn.kastatic.org/ka-youtube-converted/ypH-hDKpCY0.mp4/ypH-hDKpCY0.mp4 407 Protein synthesis and gene expression https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/regulation-of-gene-expression-and-cell-specialization/v/non-coding-rna-ncrna 2023-06-22T15:57:36.106541556Z Non-coding RNA (ncRNA) Non-coding RNAs (ncRNAs) are functional RNA molecules that don't translate into proteins. They play vital roles in cellular processes, including transcription and translation. Key examples include micro RNAs (miRNAs), ribosomal RNAs, transfer RNAs, small nucleolar RNAs (snow RNAs), and small nuclear RNAs (snRNAs). These ncRNAs help regulate gene expression, protein synthesis, and maintain cellular structures. Tracy Kim Kovach video https://cdn.kastatic.org/googleusercontent/hoAlXP7WMtzrQHMLSSp4hoPUiL1IryhDrfLobJZ-JGk82Q_DP0gyAzjXjqBFKoNf-20vwT0mUGhP9G3WUUPxSe-v Non-coding RNA (ncRNA) Non-coding RNAs (ncRNAs) are functional RNA molecules that don't translate into proteins. They play vital roles in cellular processes, including transcription and translation. Key examples include micro RNAs (miRNAs), ribosomal RNAs, transfer RNAs, small nucleolar RNAs (snow RNAs), and small nuclear RNAs (snRNAs). These ncRNAs help regulate gene expression, protein synthesis, and maintain cellular structures. https://cdn.kastatic.org/ka-youtube-converted/9YrS35wxE7o.mp4/9YrS35wxE7o.mp4 280 Protein synthesis and gene expression https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/regulation-of-gene-expression-and-cell-specialization/v/operons-and-gene-regulation-in-bacteria 2023-06-22T09:32:02.370557018Z Operons and gene regulation in bacteria DNA regulation controls gene expression in cells, allowing different cell types to perform unique functions despite having the same DNA. Prokaryotes, like bacteria, use operons, which consist of a promoter and multiple genes. Repressors, corepressors, activators, and inducers can influence transcription by binding to regulatory DNA sequences, enabling cells to adapt to their environment. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/b400e24c-a0b6-4eb8-afdb-0a66f1a7cb8a_1280_720_base.png Operons and gene regulation in bacteria DNA regulation controls gene expression in cells, allowing different cell types to perform unique functions despite having the same DNA. Prokaryotes, like bacteria, use operons, which consist of a promoter and multiple genes. Repressors, corepressors, activators, and inducers can influence transcription by binding to regulatory DNA sequences, enabling cells to adapt to their environment. https://cdn.kastatic.org/ka-youtube-converted/N7_K0yl0Egk.mp4/N7_K0yl0Egk.mp4 610 Protein synthesis and gene expression https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/regulation-of-gene-expression-and-cell-specialization/v/trp-operon 2023-08-07T17:09:37.131449861Z Trp operon The Trp operon plays a crucial role in tryptophan production, an essential amino acid. In E. Coli, the operon consists of genes and regulatory DNA sequences, including the promoter and operator. Tryptophan acts as a co-repressor, binding to the Trp repressor and inhibiting transcription when abundant. Additionally, feedback inhibition occurs, where tryptophan directly inhibits enzyme activity. This regulation ensures efficient resource use and tryptophan biosynthesis. Sal Khan video https://cdn.kastatic.org/googleusercontent/cKDhNPbg9NwEQ7BrZohPiRZrtMBng84NsP5NfM08vY5NVmWEzHj4gR9l1fJMg-PLkEosYyOEaDab_R1THXsKD_yj Trp operon The Trp operon plays a crucial role in tryptophan production, an essential amino acid. In E. Coli, the operon consists of genes and regulatory DNA sequences, including the promoter and operator. Tryptophan acts as a co-repressor, binding to the Trp repressor and inhibiting transcription when abundant. Additionally, feedback inhibition occurs, where tryptophan directly inhibits enzyme activity. This regulation ensures efficient resource use and tryptophan biosynthesis. https://cdn.kastatic.org/ka-youtube-converted/EvLy_1_Y3tk.mp4/EvLy_1_Y3tk.mp4 396 Protein synthesis and gene expression https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/regulation-of-gene-expression-and-cell-specialization/a/the-trp-operon 2021-04-29T07:54:44Z The trp operon How the trp repressor controls expression gene expression. Feedback inhibition & attenuation. article https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/regulation-of-gene-expression-and-cell-specialization/v/lac-operon 2023-06-22T09:32:02.370557018Z Lac operon The lac operon in E. coli regulates lactose metabolism. It consists of three genes (lacZ, lacY, and lacA) and is controlled by a promoter, operator, and CAP site. Lactose presence triggers allolactose production, which inhibits the lac repressor, allowing transcription. Glucose levels impact transcription through cyclic AMP and the catabolite activator protein. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/636235f8-42bd-4ecf-b2f9-31e8afc08d5e_1280_720_base.png Lac operon The lac operon in E. coli regulates lactose metabolism. It consists of three genes (lacZ, lacY, and lacA) and is controlled by a promoter, operator, and CAP site. Lactose presence triggers allolactose production, which inhibits the lac repressor, allowing transcription. Glucose levels impact transcription through cyclic AMP and the catabolite activator protein. https://cdn.kastatic.org/ka-youtube-converted/LuOaEe89_HE.mp4/LuOaEe89_HE.mp4 665 Protein synthesis and gene expression https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/regulation-of-gene-expression-and-cell-specialization/a/the-lac-operon 2021-04-29T07:53:47Z The lac operon Regulation of genes for lactose utilization. lac repressor, catabolite activator protein, and cAMP. article