Replicacao

Genética\ue601 \ue601Relembrando:\ue601\ue601 - Genética\ue601é\ue601o\ue601estudo\ue601dos\ue601genes\ue601 - Genes:\ue601porção\ue601de\ue601uma\ue601molécula\ue601de\ue601DNA\ue601 que\ue601carrega\ue601uma\ue601informação\ue601especí\ufb01ca\ue601 para\ue601a\ue601formação\ue601de\ue601uma\ue601proteína\ue601\ue601 - DNA\ue601armazena\ue601a\ue601informação\ue601e\ue601RNA\ue601 transfere\ue601a\ue601informação\ue601\ue601 - A\ue601sequência\ue601em\ue601que\ue601os\ue601genes\ue601estão\ue601 organizados,\ue601essa\ue601sequência\ue601de\ufb01ne\ue601as\ue601 características\ue601que\ue601vão\ue601ser\ue601 manifestadas\ue601 - Genoma\ue601é\ue601a\ue601quantidade\ue601e\ue601sequência\ue601 total\ue601de\ue601genes\ue601que\ue601existem\ue601nos\ue601núcleos\ue601 das\ue601células\ue601humanas\ue601 Replicação\ue601\ue601 Ideia\ue601da\ue601necessidade\ue601de\ue601passar\ue601o\ue601material\ue601 genético\ue601adiante.\ue601Pode\ue601ser\ue601chamada\ue601de\ue601 duplicação\ue601do\ue601material\ue601genético\ue601\ue601 Antes\ue601de\ue601uma\ue601divisão\ue601células,\ue601o\ue601material\ue601 genético\ue601sempre\ue601sofre\ue601duplicação\ue601para\ue601 manter\ue601a\ue601quantidade\ue601certa\ue601de\ue601material.\ue601 Produz\ue601duas\ue601novas\ue601cadeias,\ue601utilizando\ue601 como\ue601molde\ue601duas\ue601cadeias\ue601antigas\ue601 Existem\ue601três\ue601modelos\ue601de\ue601replicação:\ue601\ue601 1. Semiconservativa:\ue601a\ue601\ufb01ta\ue601dupla\ue601da\ue601 molécula\ue601mãe\ue601é\ue601aberta,\ue601onde\ue601cada\ue601uma\ue601 das\ue601vidas\ue601será\ue601utilizada\ue601para\ue601 construção\ue601de\ue601uma\ue601nova\ue601\ufb01ta\ue601por\ue601 pareamento\ue601de\ue601bases.\ue601Cada\ue601uma\ue601das\ue601 \ufb01tas\ue601possuirá\ue601em\ue601sua\ue601composição\ue601uma\ue601 \ufb01ta\ue601da\ue601molécula\ue601mãe,\ue601por\ue601isso\ue601 semiconservativa.\ue601 2. Conservativa:\ue601a\ue601molécula\ue601mãe\ue601irá\ue601de\ue601 conservar\ue601após\ue601a\ue601produção\ue601e\ue601outra\ue601 molécula\ue601será\ue601produzida\ue601utilizando\ue601o\ue601 molde\ue601(duas\ue601moléculas\ue601de\ue601DNA\ue601 parentais\ue601formam\ue601uma\ue601molécula\ue601nova)\ue601\ue601 3. Dispersiva:\ue601parte\ue601da\ue601molécula\ue601irá\ue601se\ue601 mantes\ue601simples\ue601e\ue601outra\ue601\ufb01cará\ue601dupla,\ue601 como\ue601uma\ue601mistura\ue601entre\ue601molécula\ue601nova\ue601 e\ue601molécula\ue601antiga\ue601(\ue601a\ue601molécula\ue601nova\ue601é\ue601 formada\ue601a\ue601partir\ue601de\ue601fragmentos\ue601de\ue601 DNA)\ue601 O\ue601verdadeiro\ue601modelo\ue601de\ue601replicação\ue601é\ue601o\ue601 semiconservativo,\ue601por\ue601isso\ue601que\ue601as\ue601duas\ue601 estruturas\ue601moldadas\ue601precisam\ue601ser\ue601 idênticas\ue601a\ue601molécula\ue601inicial\ue601-\ue601mesma\ue601 informação\ue601genética,\ue601 A\ue601replicação\ue601sempre\ue601se\ue601inicia\ue601em\ue601uma\ue601 região\ue601chamada\ue601de\ue601Origem\ue601da\ue601Replicação,\ue601 que\ue601é\ue601uma\ue601região\ue601especí\ufb01ca\ue601do\ue601DNA,\ue601rica\ue601 em\ue601timina\ue601e\ue601adeninas\ue601(apenas\ue601duas\ue601 ligações\ue601de\ue601hidrogênio)\ue601que\ue601possuem\ue601 ligações\ue601mais\ue601fracas,\ue601facilitando\ue601a\ue601 abertura\ue601da\ue601dupla\ue601hélice\ue601é\ue601a\ue601formação\ue601da\ue601 forquilha\ue601de\ue601replicação.\ue601 Bolha\ue601de\ue601replicação:\ue601estrutura\ue601de\ue601enzimas\ue601 formada\ue601na\ue601forquilha\ue601de\ue601réplica,\ue601as\ue601 enzimas\ue601dessa\ue601estrutura\ue601são\ue601responsáveis\ue601 pela\ue601replicação.\ue601Cada\ue601forquilha\ue601apresenta\ue601 uma\ue601bolha\ue601diferente\ue601e\ue601cada\ue601bolha\ue601vai\ue601para\ue601 um\ue601lado\ue601diferente.\ue601 Raquel Roani T25/ T2 Genética\ue601 A\ue601replicação\ue601do\ue601DNA\ue601chega\ue601ao\ue601\ufb01m\ue601 quando\ue601duas\ue601forquilhas\ue601se\ue601encontram,\ue601 esse\ue601processo\ue601pode\ue601levar\ue601até\ue60110\ue601horas.\ue601 Processo:\ue601 - Em\ue601algum\ue601ponto\ue601do\ue601DNA\ue601ocorrerá\ue601a\ue601 formação\ue601de\ue601uma\ue601origem\ue601de\ue601replicação,\ue601 nesse\ue601momento\ue601um\ue601sinal\ue601bioquímico\ue601de\ue601 replicação\ue601ativa\ue601a\ue601proteína\ue601ORC\ue601 (proteína\ue601de\ue601origem),\ue601que\ue601se\ue601liga\ue601na\ue601 região\ue601da\ue601sequência\ue601consenso\ue601e\ue601se\ue601liga\ue601 a\ue601enzima\ue601helicase\ue601-\ue601responsável\ue601pela\ue601 abertura\ue601das\ue601\ufb01tas\ue601de\ue601DNA\ue601 - As\ue601enzimas\ue601helicases\ue601deslizam\ue601e\ue601fazem\ue601 a\ue601abertura\ue601da\ue601forquilha\ue601de\ue601replicação\ue601e\ue601 em\ue601cima\ue601delas\ue601ocorre\ue601a\ue601formação\ue601da\ue601 bolha\ue601de\ue601réplica,\ue601que\ue601anda\ue601lateralmente\ue601 do\ue601sentido\ue601da\ue601via,\ue601quebrando\ue601as\ue601pontes\ue601 de\ue601hidrogênio\ue601e\ue601replicando\ue601o\ue601DNA\ue601\ue601 - A\ue601replicação\ue601vai\ue601ocorrer\ue601com\ue601base\ue601na\ue601 abertura\ue601de\ue601\ufb01tas\ue601e\ue601no\ue601recrutamento\ue601das\ue601 origens\ue601de\ue601replicação\ue601por\ue601meio\ue601das\ue601 ORCs.\ue601 *A\ue601leitura\ue601da\ue601\ufb01ta\ue601molde\ue601é\ue601feita\ue601no\ue601sentido\ue601 3\u02bc\ue601>\ue6015\u02bc\ue601para\ue601que\ue601a\ue601formação\ue601da\ue601nova\ue601\ufb01ta\ue601 seja\ue601no\ue601sentido\ue6015\u02bc\ue601>\ue6013\u02bc\ue601 A\ue601replicação\ue601não\ue601é\ue601contínua\ue601de\ue601ambos\ue601os\ue601 lados,\ue601apenas\ue601um\ue601lado\ue601vai\ue601contínuo.\ue601 A\ue601\ufb01ta\ue601nova\ue601que\ue601estiver\ue601no\ue601mesmo\ue601sentido\ue601 da\ue601abertura\ue601vai\ue601ser\ue601construída\ue601 continuamente,\ue601a\ue601outra\ue601vai\ue601sendo\ue601 adicionada\ue601aos\ue601poucos,\ue601com\ue601as\ue601enzimas\ue601 indo\ue601e\ue601voltando,\ue601pois\ue601ela\ue601está\ue601em\ue601sentido\ue601 contrário\ue601a\ue601abertura,\ue601então\ue601o\ue601espaço\ue601vai\ue601 se\ue601abrindo\ue601para\ue601atrás\ue601de\ue601onde\ue601ela\ue601está.\ue601 Por\ue601ela\ue601ser\ue601antiparalela.\ue601 \ue601 Enzimas\ue601de\ue601replicação\ue601\ue601 \u2022 Girase/topoisomerase:\ue601responsável\ue601por\ue601 rotacional\ue601o\ue601DNA\ue601enquanto\ue601ele\ue601é\ue601 replicado,\ue601para\ue601que\ue601a\ue601\ufb01ta\ue601não\ue601se\ue601 tensione\ue601e\ue601impedindo\ue601a\ue601quebra\ue601da\ue601\ufb01ta\ue601 \u2022 Helicase:\ue601abre\ue601a\ue601\ufb01ta\ue601dupla\ue601a\ue601partir\ue601do\ue601 rompimento\ue601das\ue601pontes\ue601de\ue601hidrogênio.\ue601 Ocorre\ue601o\ue601gasto\ue601de\ue601A TP\ue601 Raquel Roani T25/ T2 Genética\ue601 \u2022 DNA\ue601polimerase\ue601III:\ue601constrói\ue601material\ue601 genético\ue601a\ue601partir\ue601da\ue601polimerização\ue601dos\ue601 nucleotídeos,\ue601revisa\ue601e\ue601quebra\ue601 fragmentos\ue601com\ue601erros.\ue601Na\ue601\ufb01ta\ue601continua\ue601 a\ue601enzima\ue601também\ue601estará\ue601continua,\ue601já\ue601na\ue601 \ufb01ta\ue601descontínua\ue601ela\ue601precisa\ue601se\ue601mover\ue601 constantemente\ue601\ue601 \u2022 DNA\ue601polimerase\ue601I:\ue601corrige\ue601e\ue601retira\ue601os\ue601 primers\ue601,\ue601porém\ue601deixa\ue601uma\ue601ligação\ue601 fosfodiester\ue601aberta.\ue601T ransforma\ue601a\ue601parte\ue601 de\ue601RNA\ue601em\ue601DNA.\ue601 \u2022 DNA\ue601polimerase\ue601II:\ue601atua\ue601em\ue601casos\ue601 especí\ufb01cos\ue601de\ue601reparo.\ue601\ue601 \u2022 Ligase:\ue601responsável\ue601por\ue601fechar\ue601a\ue601 ligação\ue601fosfordiester\ue601que\ue601foi\ue601deixada\ue601 aberta\ue601pela\ue601polimerase\ue601I\ue601e\ue601une\ue601os\ue601 fragmentos\ue601de\ue601okasaki\ue601à\ue601\ufb01ta\ue601de\ue601DNA\ue601 recém\ue601sintetizada\ue601 \u2022 SSB:\ue601na\ue601separação\ue601das\ue601\ufb01tas\ue601ela\ue601se\ue601liga\ue601 as\ue601\ufb01tas\ue601simples\ue601para\ue601que\ue601elas\ue601não\ue601 voltem\ue601a\ue601se\ue601ligar ,\ue601mantendo\ue601a\ue601forquilha\ue601 de\ue601replicação\ue601 \u2022 Carregador\ue601de\ue601grampo:\ue601adiciona\ue601um\ue601 grandão\ue601responsável\ue601por\ue601manter\ue601a\ue601\ufb01ta\ue601 molde\ue601presa\ue601a\ue601\ufb01ta\ue601que\ue601está\ue601se\ue601 formando.\ue601T oda\ue601vez\ue601que\ue601a\ue601\ufb01ta\ue601 descontínua\ue601precisa\ue601ser\ue601trocada\ue601o\ue601 grampo\ue601se\ue601desprende\ue601e\ue601volta\ue601a\ue601se\ue601unir\ue601 quando\ue601a\ue601outra\ue601\ufb01ta\ue601é\ue601adicionada\ue601 \u2022 Primase:\ue601adiciona\ue601o\ue601primer\ue601(molécula\ue601de\ue601 RNA)\ue601na\ue601\ufb01ta\ue601que\ue601está\ue601se\ue601formando\ue601 \u2022 T elomerase:\ue601leva\ue601uma\ue601curta\ue601molécula\ue601de\ue601 RNA\ue601para\ue601a\ue601\ufb01ta\ue601\ufb01lha,\ue601para\ue601ser\ue601usada\ue601 como\ue601molde,\ue601evitando,\ue601assim,\ue601perdas\ue601 cromossômicas\ue601\ue601 \u2022 Fatores\ue601de\ue601montagem\ue601da\ue601cromatina:\ue601 retira\ue601o\ue601nucleosídeo\ue601da\ue601frente\ue601da\ue601 forquilha\ue601de\ue601replicação\ue601e\ue601reposiciona\ue601 após\ue601a\ue601forquilha\ue601 Processo:\ue601 - A\ue601helicase\ue601vai\ue601quebrar\ue601as\ue601pontes\ue601de\ue601 hidrogênio\ue601(\ue601aqui\ue601ocorre\ue601gasto\ue601de\ue601A TP)\ue601 e,\ue601em\ue601conjunto\ue601com\ue601a\ue601girase,\ue601vão\ue601 rotacional\ue601o\ue601DNA\ue601para\ue601reduzir\ue601a\ue601sua\ue601 tensão.\ue601Após\ue601isso\ue601a\ue601proteína\ue601SSBP\ue601se\ue601 liga\ue601as\ue601\ufb01tas\ue601simples\ue601para\ue601protegê-las,\ue601a\ue601 primase\ue601vai\ue601sintetizar\ue601um\ue601primer\ue601no\ue601 carbono\ue6013\u02bc\ue601da\ue601\ufb01ta\ue601que\ue601está\ue601se\ue601formando\ue601\ue601 - A\ue601polimerase\ue601III\ue601se\ue601liga\ue601ao\ue601primer\ue601e\ue601inicia\ue601 a\ue601polimerização\ue601dos\ue601nucleotídeos\ue601 (formação\ue601do\ue601fragmento\ue601de\ue601Okazaki).\ue601A\ue601 polimerase\ue601I\ue601retira\ue601os\ue601primers\ue601e\ue601a\ue601liga-se\ue601 une\ue601o\ue601fragmento\ue601de\ue601Okazaki\ue601a\ue601\ufb01ta\ue601 recém\ue601sintetizada,\ue601a\ue601telomerase\ue601se\ue601liga\ue601 na\ue601ponta\ue601dessa\ue601\ufb01ta\ue601\ufb01lha\ue601e\ue601deposita\ue601uma\ue601 curta\ue601\ufb01ta\ue601de\ue601RNA,\ue601que\ue601vai\ue601servir\ue601como\ue601 molde\ue601depois.\ue601 No\ue601processo\ue601descontínuo\ue601são\ue601formados\ue601 vários\ue601fragmentos\ue601de\ue601Okazaki,\ue601de\ue601dentro\ue601 para\ue601fora\ue601da\ue601forquilha\ue601de\ue601replicação.\ue601A\ue601 enzima\ue601ligase\ue601é\ue601responsável\ue601por\ue601unir\ue601 esses\ue601fragmentos,\ue601ligando\ue601o\ue601recém\ue601 sintetizado\ue601ao\ue601sinterizado\ue601anteriormente\ue601a\ue601 ele.\ue601Para\ue601a\ue601progressão\ue601dessa\ue601síntese\ue601é\ue601 necessária\ue601a\ue601adição\ue601de\ue601mais\ue601primers.\ue601 Raquel Roani T25/ T2

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Genética Humana

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Genética Humana

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