4. genetica
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Genética
Psy. Víctor Becerril
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Descubrimiento del ADN n Darwin > Mendel n Watson y Crick (1953)
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Mapa cromosómico
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Gen n Equivale a la información químico-
estructural contenida en el núcleo de las células y que al ser descifrada se traduce en una proteína o enzima.
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ADN n Lo constituyen una serie de moléculas
químicas que son: – Las bases púricas y pirimídicas – Adenina, Guanina, Timina, Citosina – Un azúcar (desoxiribosa) – Un grupo fosfato
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Composición de los Nucleótidos n Cada nucleótido contiene una base
nitrogenada. n Estas bases se clasifican en:
– Purinas: Con dos anillos, uno de cinco y otro de seis átomos.
– Pirimidinas: Con un solo anillo de seis átomos.
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Composición de los Nucleótidos n Bases púricas:
– Están formadas por la condensación de dos ciclos de carbono y nitrógeno. Para el DNA y el RNA nos interesa saber que hay dos bases púricas, la adenina y la guanina, que se encuentran en ambos.
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Composición de los Nucleótidos n La pirimidina:
– Es un compuesto orgánico, similar al benceno, pero con un anillo heterocíclico: dos átomos de nitrógeno sustituyen al carbono en las posiciones 1 y 3.
– Se degrada en sustancias muy solubles como alanina beta y aminoisobutirato beta, precursores de acetil-CoA y succinil-CoA.
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Composición de los Nucleótidos n En el ARN, la complementaria de la
adenina (A) es el uracilo (U), en vez de la timina (T)
n A=U (doble enlace) n G≡C (triple enlace)
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Composición de los Nucleótidos n Tres bases de los ácidos nucleicos
(citosina, timina y uracilo) son derivados pirimidínicos. En el ADN, estas bases forman puentes de hidrógeno con sus purinas complementarias.
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Composición de los Nucleótidos n En el ARN, la complementaria de la
adenina (A) es el uracilo (U), en vez de la timina (T)
n A=U (doble enlace) n G≡C (triple enlace)
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Nucléotido
n Es la unidad genética n Al unirse forman ADN n Una secuencia de ADN forma un Gen n Miles de genes forman Cromosomas
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n Los nucleótidos dan el código guía y pone los límites a la manera en que las células del cerebro maduran y establecen sinapsis en respuesta a todo tipo de estímulos, tanto internos como externos (epigénesis)
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Adenina Guanina Timina Citosina Uracilo
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Proyecto Genoma Humano
n Es la ordenación y localización precisa de las bases en el genoma, conjunto de genes del humano y otras especies.
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Código genético n El Genoma es como un
libro que puede fotocopiarse (replicarse) y leerse a sí mismo (traducción).
n Una proteína no es más que una forma en que un gen tiene para hacer otro gen.
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Código genético n Genotipo:
– Es la configuración genética de un individuo.
n Fenotipo: – Es la expresión del
genotipo.
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Métodos de investigación genética n Estudios en Familias. n Estudios en Gemelos. n Estudios en sujetos dados en
adopción. n Estudios del modo de transmisión
Genética. n Estudios de mapeo genético.
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7q31
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Functions of RNA Molecules n mRNA n Messenger RNA (mRNA) encodes the sequence of amino acids within a
polypeptide. In bacteria, some mRNAs encode a single polypeptide. Other mRNAs are polycistronic—a single mRNA encodes two or more polypeptides. In most species of eukaryotes, each mRNA usually encodes a single polypeptide. However, in some species, such as Caenorhabditis elegans (a nematode worm), polycistronic mRNAs are relatively common.
n tRNA n Transfer RNA (tRNA) is necessary for the translation of mRNA.
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Functions of RNA Molecules n rRNA n Ribosomal RNA (rRNA) is necessary for the translation of mRNA. Ribosomes
are composed of both rRNAs and protein subunits. n MicroRNA MicroRNAs (miRNAs) are short RNA molecules that are involved
in gene regulation in eukaryotes. n scRNA n Small cytoplasmic RNA (scRNA) is found in the cytoplasm of bacteria and
eukaryotes. In bacteria, scRNA is needed for protein secretion. An example in eukaryotes is 7S RNA, which is necessary in the targeting of proteins to the endoplasmic reticulum. It is a component of a complex known as signal recognition particle (SRP), which is composed of 7S RNA and six different protein subunits.
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Functions of RNA Molecules n RNA of RNaseP n RNaseP is a catalyst necessary in the processing of tRNA molecules.
The RNA is the catalytic component. RNaseP is composed of a 350- to 410-nucleotide RNA and one protein subunit.
n snRNA n Small nuclear RNA (snRNA) is necessary in the splicing of eukaryotic
pre-mRNA. snRNAs are components of a spliceosome, which is composed of both snRNAs and protein subunits. The structure and function of spliceosomes are examined later in this chapter.
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Functions of RNA Molecules n Telomerase RNA n The enzyme telomerase, which is involved in the replication of eukaryotic
telomeres, is composed of an RNA molecule and protein subunits. n snoRNA n Small nucleolar RNA (snoRNA) is necessary in the processing of eukaryotic
rRNA transcripts. snoRNAs are also associated with protein subunits. In eukaryotes, snoRNAs are found in the nucleolus, where rRNA processing and ribosome assembly occur.
n Viral RNAs n Some types of viruses use RNA as their genome, which is packaged within
the viral capsid.