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Similar questions Q. Choose the correct answer from the alternatives given. In four o clock plants, the gene for red flower colour (R) is incompletely dominant over the gene for white flower colour (r), hence the plants heterozygous for flower colour (Rr) have pink flowers. What will be the ratio of offsprings in a cross between red flowers and pink flowers? Q. In Antirrhinum, two plants with pink flowers were hybridized. The
F1 plants produced red, pink and white flowers in the proportion of 1 red, 2 pink and 1 white. What could be the genotype of the two plants used for hybridization. Red flower colour is determined by RR, and white by rr genes? Q. In Mirabilis, a hybrid for red (RR) and white (rr) flower produces pink (Rr) flower. A plant with pink flower is crossed with white flower, the expected phenotypic ratio is Q. In Mirabilis jalapa, a red-flowered plant was crossed with a white-flowered plant, which resulted in all pink-flowered plants. What are the chances of the appearance of red-flowered plants in a cross between pink-flowered and white-flowered plants? Q. In a cross between a red flowered plant and a white flowered plant, all offsprings produced bear pink flowers. This is because View More Animal GeneticsDeviation from simple dominanceMendel, during his life, made a lot of experiments and in all of them all traits had clear dominant- recessive patterns. However, in nature, lack o strict dominance is widespread. The absence of dominance of one member, of a pair of alleles over the other is quite common in most organisms. If dominance were universal, the heterozygote would always have the same phenotype as the dominant homozygote.  Incomplete dominanceWe refer to incomplete dominance (partial dominance) as these cases in which the phenotype of the heterozygote falls on some scale between the two homozygotes. To understand this, we will see it with one example: In four o’clock plants (Mirabilis jalapa) we can Gross a plant with red flower petales with another with white petales, the offspring have pink flower petales. If these pink flowered F1 plants are crossed, the F2 plants appear in a ratio of 1:2:1, having red, pink or white petals, respectively. The pink flowered plants are heterozygotes in which a colour is intermediate between the red and white colours of the homozygotes. In this case, there is an Allele for red pigment colour (R1) and another Allele that results in no colour (R2, the flower petals have a white background colour). Flowers in heterozygotes (R1R2) have about half the red pigment of the flowers in red homozygotes (R1R1) because the heterozygotes have only one copy of the Allele producing colour whereas homozygotes have two copies of it. CodominanceAnother exception to simple dominance is the full expression of two alternative alleles in a heterozygote, resulting in a phenotype in which the presence of both alleles can be detected. This is called codominance (the situation in which a heterozygote shows the phenotype effects of both alleles fully and equally). The best example of the codominance, and the most universal example, is the effect of the gene that determine the A, B, AB or 0 human blood groups, which are an example of multiple alleles too. Multiple alleles result from different mutations of the same gene. Blood type is determined by the type of polysaccharides (polymer of sugars) present on the surface of red blood cells. Two different polysaccharides, A and B, can be formed. The A type is synthesized by an enzyme coded by the IAallele, and the B type by an enzyme coded by the IBallele.
A third Allele I0codes for a defective enzyme that produces neither the A nor the B type of polysaccharide.
Example – Coat color in the short horn breed of cattle or in horses. In a cross of red coat cattle with white coat cattle, progeny of roan coat is obtained. In roan coat, the red and white hairs occur in definite patches but no hair has intermediate color of red and white. PleiotropyPleiotropy is the effect of a single gene on more than one characteristic. An example is the "frizzle-trait" in chickens. The primary result of this gene is the production of defective feathers. Secondary results are both good and bad; good include increased adaptation to warm temperatures, bad include increased metabolic rate, decreased egg-laying, changes in heart, kidney and spleen. Cats that are white with blue eyes are often deaf, white cats with a blue and an yellow-orange eye are deaf on the side with the blue eye. Sickle-cell anemia is a human disease originating in warm lowland tropical areas where malaria is common. Sickle-celled individuals suffer from a number of problems, all of which are pleiotropic effects of the sickle-cell allele. Gene interactions and modified Mendelian ratiosThe collaboration of several different genes in the production of one phenotypic character (or related group of characters). Epistasis is the interaction between two or more genes to control a single phenotype. Interaction involves one gene masking or modifying the phenotypic expression of another gene. No new phenotypes are produced by this type of gene interaction. A gene that masks another gene’s expression is said to be epistatic, and a gene whose expression is masked is said to be hypostatic The ratio of phenotype 9:3:3:1 observed in the F2 offspring of parents dihybrid, from epistasis changes in relationship that are different combination of group 9:3:3:1. When epistasis take place between two gene loci, the number of phenotypes appearing in the offspring of parents dihybrid be less than four. There are six types of reports commonly recognized, three of whom have three phenotypes and the other three only two. 1. Epistasis dominant (12:3:1)When the dominant allele at a locus, for example the A allele, produces a phenotype without taking into account the condition of allelic locus, it is said that the locus A is the epistasis locus B. Moreover, since the A dominant allele is able to express all the same, in the presence of B as b, this is a case of epistasis dominant. Only when the genotype of homozygous recessive individuals is at the epistasis locus (aa), the hypostasis locus alleles (B or b) can express themselves. So genotypes A-B- and A-bb produce the same phenotype, while aaB- and aabb produce two other phenotypes. The classic 9:3:3:1 is changed to 12:3:1. 2. Recessive epistasis (9:3:4)If the recessive genotype at a locus (for example aa) suppresses the expression of alleles in the B- locus, is said that the A- loci presents a recessive epistasis on locus B-.The alleles of the hypostasis B- locus can tell only if the dominant allele is present in the locus A-. The genotypes A-B- and A-bb produce two other phenotypes. The relationship 9:3:3:1 becomes 9:3:4. 3. Gene with double cumulative effect (9:6:1)If the dominant condition (homozygous or heterozygous) at each of the two locus (but not both) has the same phenotype, the ratio of F2 becomes 9:6:1. For example, when epistasis genes are involved in the production of various quantities of a substance can be as a pigment, it can be considered that the dominant genotypes of each locus, independently produce one unit of pigment. So genotypes A-Bb and aaB- produce one unit of each pigment and then have the same phenotype. The genotype aabb not produce pigment, but in A-B- genotype effect is cumulative and is produced two units of pigment. 4. Duplicate gene action (15:1)The relationship 9:3:3:1 is changed to 15:1, if the dominant alleles of both loci each produce the same phenotype without cumulative effect. 5. Complementary gene action (9:7)Where are identical phenotypes produced by both genotypes homozygous recessive, the ratio of F2 becomes 9:7. The genotypes aaB-, A-bb and aabb produce a single phenotype: both dominant alleles if they are present together complement each other and produce a different phenotype. 6. Dominant suppression (13:3)There are only two phenotypes in the F2 when a dominant genotype on a locus (for example A-) and the recessive genotype on locus (bb) produce the same phenotype effect. So A-B-, A-bb and aabb produce a single phenotype and aaB- producing another in report 13:3. Example: Coat Color in Horses Yet another type of epistasis occurs when one gene interacts with another to modify - but not mask - a phenotype. For example, in horses, the extension gene determines whether an animal's coat color will be red or black; here, the dominant allele E produces black pigment in the coat, while the recessive allele e produces red pigment. All horses with genotype ee are therefore red, yet there are many different types of red horses. These differences exist because of the action of epistatic modifier genes. One such modifier gene is called cream dilution. The cream dilution gene has two alleles: CCr and C. The CCrallele is semidominant; it dilutes red to yellow in the heterozygous state and red to pale cream in the heterozygous state. On the other hand, the C allele has no diluting effect on coat color. Thus, horses with genotype eeCC are chestnut colored, and they have reddish-brown coats, tails, and manes. In contrast, horses with one copy of the CCR allele (genotype eeCCCR) are palomino (i.e., they have a gold coat with a white mane and tail), while horses with two copies of the CCR allele (genotype ee CCRCCR) are cremello (i.e., basically white or cream colored). Polygenic Inheritance of complex traitsPolygenic inheritance is a pattern responsible for many features that seem simple on the surface. Many traits such as height, shape, weight, color, and metabolic rate are governed by the cumulative effects of many genes. Polygenic traits are not expressed as absolute or discrete characters, as was the case with Mendel's pea plant traits. Instead, polygenic traits are recognizable by their expression as a gradation of small differences (a continuous variation). The results form a bell shaped curve, with a mean value and extremes in either direction. Conclusion
The document was created: 11. 10. 2022 09:56:32 Prepared under project CZ.1.07/2.2.00/28.0020 Innovation of study programs FA MENDELU towards internationalization of study What will be the ratio of offsprings in a cross between the red flowered and pink flowered Mirabilis jalapa plants red pink 1 1 red pink 3 1 red pink 1/3 red pink 2 3?Complete Answer:
- According to the experiment, when the plant (Rr) made in F1 generation is crossed with dominant plant i.e red coloured Mirabilis plant (RR), the offspring will be pink (Rr) and red (RR). Their genotypic ratio will be 2:2 i.e. 1:1.
What will be the ratio of offspring in a cross between the red Coloured and white Coloured flowers of Mirabilis jalapa in F1 generation?So, the correct option is '1:2:1'. Was this answer helpful?
Which Cross would give you the most pink flowered plants in Mirabilis jalapa?This can be seen in the plant snapdragon, where the cross between red and white flowered snapdragon plants results in an offspring having pink-colored flowers. So, the right answer is option B.
When pink and white flowered Mirabilis plants are crossed the genotypic and phenotypic ratio of the progeny will be :So, the correct option is '1 pink: 1 white'.
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