Chapter 1 Ciencias Biológicas 2 Teresa Audesirk Gerald Audesirk Bruce E. Byres

Chapter 1 Ciencias Biológicas 2 Capítulo 4 Herencia

Biology: Life on Earth (Audesirk) Capítulo 4: Herencia Patrones de herencia Chapter 12

Biology: Life on Earth (Audesirk) Genética Campo fundado por Gregor Mendel. Trabajó con semillas de arvejas. No tenía conocimientos acerca de células, cromosomas, etc.; sino que le interesaban las matemáticas. Su trabajo fue redescubierto después de Darwin. By the late nineteenth century, natural selection suggested that a population could evolve if members show variation in heritable traits. Variations that improved survival chances would be more common in each generation—in time, the population would change or evolve. The theory of natural selection did not fit with the prevailing view of inheritance—blending. Blending would produce uniform populations; such populations could not evolve. Many observations did not fit blending—for example, a white horse and a black horse did not produce only gray ones. Gregor Mendel used experiments in plant breeding and a knowledge of mathematics to form his hypotheses. Chapter 12

Relaciones entre genes, alelos y cromosomas Biology: Life on Earth (Audesirk) Relaciones entre genes, alelos y cromosomas Cromosoma de un parental 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Loci: El locus D contiene el gen D, que influye en la altura de la planta. Ambos cromosomas tienen el mismo alelo del gen D. Esta planta de tomate es homocigota respecto de este gen. El locus M contiene el gen M, que influye en el color de las hojas. Esta planta de tomate es homocigota respecto de este gen. El locus Bk contiene el gen Bk, que influye en la forma del fruto. Cada cromosoma tiene un alelo diferente del gen Bk. Esta planta de tomate es heterocigota respecto de este gen. Each homologous chromosome carries the same set of genes. Each gene is located at the same relative position, or locus, on its chromosome. Differences in nucleotide sequences at the same gene locus produce different alleles of the gene. Diploid organisms have two alleles of each gene. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Loci: Cromosoma homólogo del otro parental Chapter 12

Semillas y flores del guisante (arveja) comestible Biology: Life on Earth (Audesirk) Semillas y flores del guisante (arveja) comestible Estambres (masculinos producen polen) Carpelo (femenino contiene óvulos) In the intact pea flower (left), the lower petals form a container enclosing the reproductive structures—the stamens (male) and carpel (female). Pollen normally cannot enter the flower from outside, so peas normally self-fertilize. Flor de chícharo intacta Flor disectada para mostrar las estructuras reproductoras Chapter 12

Biology: Life on Earth (Audesirk) Definiciones Rasgo — Una característica variable del organismo. Gen — Un segmento de ADN que tiene una función y está situado en un lugar específico del cromosoma. Locus — Ubicación específica de un gen en un cromosoma. Must know these!!! Trait—A variable characteristic of organism. It’s something about the organism’s appearance, behavior, etc., that you’re interested in. Gene—A segment of chromosomal DNA controlling a specific trait. This refers to the genetic material that produces a product that determines the trait. Locus—The chromosomal position where a specific gene lives. This is the gene’s address, in terms of which chromosome does it live on and where on that chromosome does it live? Genome—Refers to all standard loci for a species. We can speak of the “human genome.” It is the list of the genes that humans have. Chapter 12

Biology: Life on Earth (Audesirk) Definiciones Genoma — Juego completo de genes que posee un miembro de una especie determinada. Alelos — Una de varias formas alternativas de un gen específico. “Color de la flor” es un gen; “Púrpura” es un alelo del color de la flor. “Blanco” es otro alelo del color de la flor. Must know these!!! Trait—A variable characteristic of organism. It’s something about the organism’s appearance, behavior, etc., that you’re interested in. Gene—A segment of chromosomal DNA controlling a specific trait. This refers to the genetic material that produces a product that determines the trait. Locus—The chromosomal position where a specific gene lives. This is the gene’s address, in terms of which chromosome does it live on and where on that chromosome does it live? Genome—Refers to all standard loci for a species. We can speak of the “human genome.” It is the list of the genes that humans have. Chapter 12

Definiciones Genotipo— Composición genética de un organismo; los alelos de cada gen que el organismo tiene efectivamente. Homocigoto — Organismo que tiene dos copias del mismo alelo de un gen determinado. El padre dona el alelo para el color púrpura de la flor. La madre dona el alelo para el color púrpura de la flor.

Biology: Life on Earth (Audesirk) Definiciones Heterocigoto — Los alelos materno y paterno diferentes. El padre dona el alelo para el color púrpura de la flor. La madre dona el alelo para el color blanco de la flor. Fenotipo — Características físicas de un organismo. Es la apariencia externa del individuo. 1. Alleles are various molecular forms of a gene for the same trait. 2. If homozygous, both alleles are the same. 3. If heterozygous, the alleles differ. 4. When heterozygous, one allele is dominant (A), and the other is recessive (a). 5. Thus, homozygous dominant = AA, homozygous recessive = aa, and heterozygous = Aa. 6. Genotype is the sum of the genes, and phenotype is how the genes are expressed (what you observe). Example: Homozygous—Maternal & paternal alleles same Dad donates blue-eyed allele Mom donates blue-eyed allele Heterozygous—Maternal & paternal alleles differ Mom donates brown-eyed allele Chapter 12

Biology: Life on Earth (Audesirk) Definiciones Dominante — Alelo que expresa un 100% del fenotipo de los heterocigotos. Recesivo — Alelo que se expresa únicamente en homocigotos. Dominancia incompleta — El fenotipo heterocigótico es intermedio entre los dos fenotipos homocigotos. Phenotype—List of traits exhibited by individual Doesn’t always reveal genotype. Sometimes the presence of a dominant allele on the maternal chromosome will mask the presence of a recessive allele on the other chromosome. Dominant—Allele that is expressed 100% in heterozygote Recessive—Allele is not expressed at all in heterozygote but only in homozygote. Incomplete dominance—heterozygote displays intermediate version of the trait about half way between the full two homozygous phenotypes. Chapter 12

Simbología en genética Biology: Life on Earth (Audesirk) Simbología en genética Se utiliza la letra inicial para el alelo dominante. Letra mayúscula representa al dominante. Minúscula de la misma letra representa al recesivo. Si la flor púrpura es dominante sobre la flor blanca… “P” representa al alelo para púrpura. “p” representa al alelo para blanca. Often use initial letter of dominant allele Capital letter represents dominant Lower case of same letter represents recessive If black fur dominant to white… B represents allele for black b represents allele for white Chapter 12

Biology: Life on Earth (Audesirk) Polinización cruzada Polen polinización cruzada Polen P P Planta de flor púrpura de raza pura Mendel pea experiments, flower color: cross fertilization of parental generation. Planta de flor blanca de raza pura F1 Todas las plantas de flor púrpura Chapter 12

Auto-polinización de F2 Biology: Life on Earth (Audesirk) Auto-polinización de F2 F1 75% Púrpura 25% Blanca Auto-polinización Mendel pea experiments, flower color: self-fertilization of F2. F2 F2 F2 F2 Chapter 12

Biology: Life on Earth (Audesirk) Genotipo vs fenotipo El fenotipo es cómo nosotros nos vemos, la apariencia. Flores púrpura. Flores blancas. El genotipo es lo que dicen nuestros genes. Flores blancas / Flores blancas. Flores blancas / Flores púrpura. Flores púrpura / Flores púrpura. Phenotype is how we look/behave Brown eyes Blue eyes Genotype is what our genes say BlueEyes/BlueEyes BlueEyes/BrownEyes BrownEyes/BrownEyes Chapter 12

Biology: Life on Earth (Audesirk) Genotipo vs fenotipo Genotipos PP = homocigoto para flor púrpura. pp = homocigoto para Flor blanca. Pp = heterocigoto para el color de la flor. Fenotipos del genotipo: PP = Flor púrpura. Pp = Flor púrpura. pP = Flor púrpura. pp = Flor blanca. BB = homozygous for black fur bb = homozygous for white fur Bb = heterozygous for fur color Phenotypes: BB = Black Bb = Black bB = Black bb = White Chapter 12

Gametos de homocigotos Progenitor homocigoto Gametos A A A A Todos los gametos tienen el mismo alelo de ese gen

Gametos de heterocigotos Progenitor heterocigoto Gametos A a A a Igual número de gametos con cada uno de los dos alelos

Homocigoto dominate Homocigoto recesivo Biology: Life on Earth (Audesirk) Homocigoto dominate Homocigoto recesivo PP homocigoto dominante P P Progenitor púrpura espermatozoides y óvulos todos P Mendel pea experiments, flower color: gametes of a homozygous parent pp homocigoto recesivo p p Progenitor blanco espermatozoides y óvulos todos p Chapter 12

Biology: Life on Earth (Audesirk) Espermatozoides P + óvulos p producen la misma F1 que espermatozoides p + óvulos P Biology: Life on Earth (Audesirk) espermatozoides P + p F1 Púrpura óvulos Pp espermatozoides Mendel pea experiments, flower color: F1 generation from homozygous parents p + P F1 Púrpura óvulos Pp Chapter 12

Biology: Life on Earth (Audesirk) Cruzamiento Pp X Pp descendencia F2 espermatozoides y óvulos de plantas F1 P Homocigoto dominante púrpura (PP) + P P Heterocigoto púrpura (Pp) + p p Heterocigoto púrpura (Pp) Mendel pea experiments, flower color: F2 from heterozygous F1 + P p Homocigoto recesivo blanco (pp) + p Chapter 12

Usando el cuadro de Punnett para cruzamientos en genética Biology: Life on Earth (Audesirk) Usando el cuadro de Punnett para cruzamientos en genética El cuadro de Punnett, denominado así en honor al famoso genetista Reginald Punnett. Es un procedimiento intuitivo para predecir los genotipos y fenotipos de la progenie. Considera únicamente los genes de interés. Genotipo del espermatozoide en la columna. Genotipo del óvulo en la fila. Se llena el cuadro con el genotipo del cigoto. Named after geneticist Reginald Punnett Figured using Punnett squares Considers only genes of interest List all possible sperm genotypes across top List all possible egg genotypes down side Fill in boxes with zygote genotypes Chapter 12

Biology: Life on Earth (Audesirk) Considerando el color de la flor Supongamos que el color de la flor es afectado por un único gen (cruzamiento monohíbrido). Asumamos que todos los alelos son púrpura o blanco. Púrpura (P) es dominante sobre blanco (p). El heterocigoto tendrá tantas flores púrpura como el homocigoto dominante. Other genes also affect eye color, but we will pretend there is only one gene and that it has only two alles Eye color affected mainly by one gene (monohybrid cross) Most common alleles are brown and blue Blue is recessive to brown Heterozygotes have eyes as brown as homozygous dominants Chapter 12

Haciendo un cuadro de Punnett: heterocigoto X heterocigoto Biology: Life on Earth (Audesirk) Haciendo un cuadro de Punnett: heterocigoto X heterocigoto P p Óvulos de planta heterocigota P P P P p Polen de planta heterocigota Note: You should be very familiar with how to work these. In a cross between two heterozygotes involving dominant and recessive alleles: 1/4 of the offspring will typically show the recessive phenotype because they are homozygous for the recessive allele. 3/4 will have the dominant phenotype, even though 2/3 of these (1/2 total) are heterozygous. The Punnett square method allows you to predict both genotypes and phenotypes of specific crosses; here we use it for a cross between plants that are heterozygous for a single trait, flower color. (1) Assign letters to the different alleles; use uppercase for dominant and lowercase for recessive. (2) Determine all the types of genetically different gametes that can be produced by the male and female parents. (3) Draw the Punnett square, with each row and column labeled with one of the possible genotypes of sperm and eggs, respectively. (We have included the fractions of these genotypes with each label.) (4) Fill in the genotype of the offspring in each box by combining the genotype of sperm in its row with the genotype of the egg in its column. (We have placed the fractions in each box.) (5) Count the number of offspring with each genotype. (Note that Pp is the same as pP.) (6) Convert the number of offspring of each genotype to a fraction of the total number of offspring. In this example, out of four fertilizations, only one is predicted to produce the pp genotype, so 1/4 of the total number of offspring produced by this cross is predicted to be white. To determine phenotypic fractions, add the fractions of genotypes that would produce a given phenotype. For example, purple flowers are produced by 1/4 PP + 1/4 Pp + 1/4 pP, for a total of 3/4 of the offspring. p P p p p Frecuencias Fenotipos Genotipos PP p P P p p 2 1 1 Púrpura Blanca 3 (75%) 1(25%) Chapter 12

Cruzamiento de prueba: heterocigoto X homocigoto Biology: Life on Earth (Audesirk) Cruzamiento de prueba: heterocigoto X homocigoto Óvulos de un homocigoto recesivo p p P P P P p Polen de una planta desconocida con fenotipo dominate (heterocigoto) p p p p p Frecuencias Fenotipos Genotipos Pp p P p p 2 2 Púrpura Blanca (50%) (50%) Chapter 12

Cruzamiento de prueba: homocigoto X homocigoto recesivo Biology: Life on Earth (Audesirk) Cruzamiento de prueba: homocigoto X homocigoto recesivo Óvulos de un homocigoto recesivo p p P P p P p Polen de una planta desconocida con fenotipo dominate (homocigoto) P P p P p Frecuencias Fenotipos Genotipos Pp P p P p P p 4 Púrpura (100%) Chapter 12

Rasgos de las plantas de arvejas estudiadas por Mendel Biology: Life on Earth (Audesirk) Rasgos de las plantas de arvejas estudiadas por Mendel Forma de la semilla Color de la semilla Forma de la vaina Color de la vaina Color de la flor Traits of pea plants that Mendel studied Ubicación de la flor Tamaño de la planta Chapter 12

Cruzamiento dihíbrido: SsYy X SsYy Biology: Life on Earth (Audesirk) Cruzamiento dihíbrido: SsYy X SsYy Óvulos 1 4 SY 1 4 Sy 1 4 sY 1 4 sy Autopolinización de SsYy SY 1 4 1 16 1 16 1 16 1 16 SSYY SSYy SsYY SsYy Sy 1 4 1 16 1 16 1 16 1 16 SSyY SSyy SsyY Ssyy Espermatozoides Figure: FIGURE 12.6 Title: Predicting genotypes and phenotypes for a cross between gametes that are heterozygous for two traits Caption: Here we are working with both seed color and shape, with yellow (Y) dominant to green (y), and smooth (S) dominant to wrinkled (s). (a) Punnett square analysis. In this cross, both parents are heterozygous for each trait (or a single individual heterozygous for both traits self-fertilize). There are now 16 boxes in the Punnett square. In addition to predicting all the genotypic combinations, the Punnett square predicts 3/4 yellow seeds, 1/4 green seeds, 3/4 smooth seeds, and 1/4 wrinkled seeds, just as we would expect from crosses made of each trait separately. (b) Probability theory can be used to predict phenotypes that result from a cross between gametes that are heterozygous for two traits. The fraction of genotypes from each sperm and egg combination is illustrated within each box of the Punnett square. Adding the fractions for the same genotypes will give the genotypic ratios. Converting each genotype to a phenotype and then adding their numbers reveals that 3/4 of the offspring will be smooth and 1/4 will be wrinkled and that 3/4 will be yellow and 1/4 will be green. Multiplying these independent probabilities produces predictions for the phenotype of offspring. These ratios are identical to those generated by the Punnett square. sY 1 4 1 16 1 16 1 16 1 16 sSYY sSYy ssYY ssYy sy 1 4 1 16 1 16 1 16 1 16 sSyY sSyy ssyY ssyy Chapter 12

Distribución independiente Biology: Life on Earth (Audesirk) Distribución independiente Y S S Y s y S s Y y y s Chromosome movements during meiosis produce independent assortment of alleles of two different genes. Because meiosis occurs in many reproductive cells in a plant, each combination is equally likely to occur. Therefore, an F1 plant would produce gametes in the predicted proportions 1/4 SY, 1/4 sy, 1/4 sY, and 1/4 Sy. S s Y y Aleatoriamente uno o el otro y S S y Y s Y s Duplicación del cromosoma Meiosis I Meiosis II Chapter 12

Biology: Life on Earth (Audesirk) Ligamiento genético Gen del color de la flor Gen de la forma del polen Alelo púrpura, P Alelo largo, L A pea has this pair of homologous chromosomes. Alelo Rojo, p Alelo redondo, l Chapter 12

Cromosomas duplicados Cromosomas duplicados Entrecruzamiento Color de la flor Forma del polen púrpura Largo Cromosomas homólogos L l P p Cromátidas hermanas Cromosomas duplicados púrpura Largo rojo redondo Cromátidas hermanas Cromosomas duplicados rojo redondo combinación antigua P p L l P p L l L l P p P p L l P L p l P L p l L P combinación nueva p L combinación nueva P l combinación antigua l p

Determinación del sexo en mamíferos Biology: Life on Earth (Audesirk) X1 X2 Progenitor hembra Determinación del sexo en mamíferos ÓVULOS X1 X2 Xm X1 Xm X2 Xm ES P E R MATOZOIDE Figure: FIGURE 12.9 Title: Sex determination in mammals Caption: Male offspring receive their Y chromosome from the father; female offspring receive the father’s X chromosome (labeled Xm). Both male and female offspring receive an X chromosome (either X1 or X2) from the mother. Progenitor macho Y Xm Descencientes hembras Y X1 X2 Y Y Descendientes machos Chapter 12

Herencia ligada al sexo: color de los ojos en la mosca de la fruta Biology: Life on Earth (Audesirk) Herencia ligada al sexo: color de los ojos en la mosca de la fruta R r Progenitor hembra XR Xr R XR XR XR Xr Progenitor macho XRY Note: You should be very familiar with how to work these. In a cross between two heterozygotes involving dominant and recessive alleles: 1/4 of the offspring will typically show the recessive phenotype because they are homozygous for the recessive allele. 3/4 will have the dominant phenotype, even though 2/3 of these (1/2 total) are heterozygous. The Punnett square method allows you to predict both genotypes and phenotypes of specific crosses; here we use it for a cross between plants that are heterozygous for a single trait, flower color. (1) Assign letters to the different alleles; use uppercase for dominant and lowercase for recessive. (2) Determine all the types of genetically different gametes that can be produced by the male and female parents. (3) Draw the Punnett square, with each row and column labeled with one of the possible genotypes of sperm and eggs, respectively. (We have included the fractions of these genotypes with each label.) (4) Fill in the genotype of the offspring in each box by combining the genotype of sperm in its row with the genotype of the egg in its column. (We have placed the fractions in each box.) (5) Count the number of offspring with each genotype. (Note that Pp is the same as pP.) (6) Convert the number of offspring of each genotype to a fraction of the total number of offspring. In this example, out of four fertilizations, only one is predicted to produce the pp genotype, so 1/4 of the total number of offspring produced by this cross is predicted to be white. To determine phenotypic fractions, add the fractions of genotypes that would produce a given phenotype. For example, purple flowers are produced by 1/4 PP + 1/4 Pp + 1/4 pP, for a total of 3/4 of the offspring. Hembra Hembra Y XR Y Xr Macho Macho Frecuencias Fenotipos Genotipos XRXR XRXr XRY XrY 1 1 1 1 Normal Portador Normal Ojos blancos 25% 25% 25% 25% Chapter 12

Dominancia incompleta: homocigoto-X homocigoto recesivo Biology: Life on Earth (Audesirk) Óvulo de progenitor rojo Homocigoto RR R R R' R' R R' R Polen de progenitor blanco Homocigoto R'R' The inheritance of flower color in snapdragons is an example of incomplete dominance. (In such cases, we will use capital letters for both alleles, here R and R’.) Hybrids (RR’) have pink flowers, whereas the homozygotes are red (RR) or white (R’R’). Rosa Rosa R' R R' R' R Rosa Rosa Frecuencias Fenotipos Genotipos R'R R'R R'R R'R 1 Rosa (intermeda) (100%) Chapter 12

Dominancia incompleta: F1 X F1 Biology: Life on Earth (Audesirk) Dominancia incompleta: F1 X F1 Óvulos del progenitor F1 rosa heterocigoto RR' R R' R R R R R' Polen de progenitor F1 Rosa heterocigoto RR' Because heterozygotes can be distinguished from homozygous dominants, the distribution of phenotypes in the F2 generation (1/4 red: 1/2 pink: 1/4 white) is the same as the distribution of genotypes (1/4 RR: 1/2 RR’: 1/4 R’R’). (b) Graphical representation of the differences between flower color inheritance in snapdragons (incomplete dominance) and edible peas (dominance). Rojo Rosa R' R R' R' R' Rosa Blanca Frecuencias Fenotipos Genotipos Frequencias RR RR' R'R R'R' 2 1 1 Rojo Rosa Blanca (25%) (50%) (25%) Chapter 12

Biology: Life on Earth (Audesirk) madre óvulos AB Ab aB ab AaBb negro castaño obscuro castaño obscuro castaño claro AB AABB AABb AaBB AaBb castaño obscuro AAbB castaño claro AAbb castaño claro AabB Aabb azul Ab padre Color de los ojos en humanos espermatozoide castaño obscuro aABB aABb aaBB aaBb azul castaño claro castaño claro AaBb aB Figure: FIGURE 12.12 Title: Human eye color Caption: At least two separate genes, each with two incompletely dominant alleles, determine human eye color. A brown-eyed man and a brown-eyed woman, each heterozygous for both genes, could have children with five different eye colors, ranging from light blue (no dominant alleles) through light brown (two dominant alleles) to almost black (all four dominant alleles). castaño claro aABb aaBb azul azul claro ab Chapter 12

Grupo sanguíneo ABO en humanos Biology: Life on Earth (Audesirk) Grupo sanguíneo ABO en humanos Tipo de sangre Genotipo Eritrocitos Anticuerpos Puede recibir sangre Puede donar sangre Frecu-encia A AA or AO B A or O A o AB 40% B BB or BO A B or O B o AB 10% AB AB Ninguno AB, A, B, O (universal) AB (universal) 4% Figure: TABLE 12.1 Title: Human blood group characteristics Caption: O OO Ambos O O,AB, A,B (universal) 46% Chapter 12

Como leer árboles genealógios Biology: Life on Earth (Audesirk) Como leer árboles genealógios = hombre = mujer = progenitores o = individuo que manifiesta el rasgo = portador heterocigótico de un rasgo autosómico o Figure: FIGURE 12.14 Title: A family pedigree Caption: This pedigree is for a recessive trait, such as albinism. Both of the original parents are carriers. Because the allele for albinism is rare, pairing between carriers is an unlikely event. However, the chance that each of two related people will carry a rare recessive allele (inherited from a common ancestor) is much higher than normal. As a result, pairings between cousins or even closer relations are the cause of a disproportionate number of recessive diseases. In this family, pairings between cousins occurred three times—between III 3 and III 5, III 4 and IV 3, and IV 1 and IV 2. = descendientes 1 2 3 I, II, III, IV, or V = generación Chapter 12

Un pedigrí recesivo

Glóbulos rojos normales Biology: Life on Earth (Audesirk) Glóbulos rojos normales Normal red blood cells are disc-shaped with indented centers. Chapter 12

Biology: Life on Earth (Audesirk) Células en forma de hoz Figure: FIGURE 12.16b Title: Sickle-cell anemia Caption: Sickled red blood cells in a person with sickle-cell anemia occur when blood oxygen is low. In this shape they are fragile and tend to clump together, clogging capillaries. Chapter 12

Variaciones sobre el tema mendeliano A. Dominancia incompleta. B. Alelos múltiples. C. Codominancia. D. Herencia poligénica. E. Interacciones en los genes.

Variaciones sobre el tema mendeliano Efectos múltiples de un único gen. 1. Pleiotropía — Uno de los genes tiene varios efectos fenotípicos.

Investigando las anomalías genéticas humanas A. Anális del árbol genealógico. La mayoria de las anomalías genéticas humanas se deben a alelos recesivos. 1. Anemia falciforme. 2. Albinismo.

Investigando las anomalías genéticas humanas Muchas anomalías genéticas humanas se deben a alelos dominantes. 1. Para que una enfermedad dominante se transmita a los descendientes, es necesario que al menos uno de los progenitores padezca la enfemedad. La enfermedad de Huntington provoca un deterioro lento y gradual de ciertas partes del cerebro.

Investigando las anomalías genéticas humanas Anomalías humanas ligadas al sexo. Daltonismo para el verde o el rojo. Hemofilia.

Investigando las anomalías genéticas humanas No disyunción durante la meiosis. 1. Número anormal de cromosomas sexuales. a. Síndrome de Turner (XO): mujeres estériles, de baja estatura; pliegues de la piel alrededor del cuello.

Investigando las anomalías genéticas humanas No disyunción durante la meiosis (continuación). 1. Número anormal de cromosomas sexuales. b. Trisomía X (XXX): mujer fértil; no presentan síntomas perceptibles; inteligencia bajo lo normal. c. Síndrome de Klinefelter (XXY): varón estéril; presenta características sexuales secundarias mixtas.

Investigando las anomalías genéticas humanas E. No disyunción durante la meiosis (continuación). 1. Número anormal de cromosomas sexuales. d. Varones XYY: Inteligencia bajo lo normal; estatura alta, genéticamente predispuestos a la violencia.

Investigando las anomalías genéticas humanas E. No disyunción durante la meiosis (continuación). 2. Número anormal de cromosomas autosómicos. a. Trisomía 21 (Síndrome de Down): retraso mental, párpados de forma peculiar, boca pequeña con lengua prominente, defectos cardíacos y escasa resistencia en enfermedades infecciosas.

Árbol genealógico: legado de la Reina Victoria Biology: Life on Earth (Audesirk) Árbol genealógico: legado de la Reina Victoria Eduardo Duque de Kent Victoria, Princesa de Saxe-Coburg Alberto, Príncipe de Saxe-Coburg-Gotha Alberto, Príncipe de Saxe-Coburg-Gotha Eduardo VII Rey de Inglaterra Leopoldo, Duque de Albania Elena, Princesa de Waldeck -Pyrmont Luis IV, Gran Duque de Hesse-Darmsteadt Alexandra de Dinamarca Alicia, Princesa de Hesse varios hijos normales Beatriz Enrique, Príncipe de Batterburg Figure: FIGURE 12.18 Title: Hemophilia among the royal families of Europe Caption: A famous genetic pedigree involves the transmission of sex-linked hemophilia from Queen Victoria of England (seated center front, with cane, 1885) to her offspring and eventually to virtually every royal house in Europe. Because Victoria’s ancestors were free of hemophilia, the hemophilia allele must have arisen as a mutation either in Victoria herself or in one of her parents (or as a result of marital infidelity). Extensive intermarriage among royalty spread Victoria’s hemophilia allele throughout Europe. Her most famous hemophiliac descendant was great-grandson Alexis, tsarevitch (crown prince) of Russia. The Tsarina Alexandra (Victoria’s granddaughter) believed that the monk Rasputin, and no one else, could control Alexis’s bleeding. Rasputin may actually have used hypnosis to cause Alexis to cut off circulation to bleeding areas by muscular contraction. The influence that Rasputin had over the imperial family may have contributed to the downfall of the tsar during the Russian Revolution. In any event, hemophilia was not the cause of Alexis’s death; he was killed with the rest of this family by the Bolsheviks (Communists) in 1918. familia real británica actual (normal) Victoria María Isabel Zarina Alexandra Nicolás II de Rusia Federico Ernesto María Victoria Irene Alejandro Alberto Alfonso XII Victoria, Reina de España Leopoldo Mauricio hija portadora y nieto hemofílico Olga Tatiana María Anastasia Zarevich Alexis Alfonso, Príncipe heredero Juan Beatriz muerto en la infancia María Jaime Gonzalo Chapter 12

Incidencia del Síndrome de Down Biology: Life on Earth (Audesirk) Incidencia del Síndrome de Down 100 200 300 400 10 20 30 40 50 Número por cada 1000 nacimientos Figure: FIGURE 12.20 Title: Down syndrome frequency increases with maternal age Caption: The increase in frequency of Down syndrome after maternal age 35 is quite dramatic. Edad de la madre (años) Chapter 12

Fin