User:Am2314/Dihybrid cross

Lead
Dihybrid cross is a cross between two individuals with two observed traits that are controlled by two distinct genes. If one of the parents is homozygous dominant for both genes and the other parent is homozygous recessive for both genes, then the offspring will be uniformly heterozygous for both genes and will display the dominant phenotype for both traits. Self-pollination or crossing of these individuals will result in predictable ratios of both genotype and phenotype in the F2 generation. The expected phenotypic ratio of crossing heterozygous parents would be 9:3:3:1. Deviations from these expected ratios may indicate that the two traits are linked or that one or both traits has a non-Mendelian mode of inheritance.

Mendelian History
Gregor Mendel was an Austrian monk who bred peas plants in his monastery garden and compared the offspring to figure out inheritance of traits. He first started looking at individual traits, but began to look at two distinct traits in the same plant. His first experiment looking at two distinct traits was found by looking at pea color (yellow or green) and pea shape (round or wrinkled). He applied the same rules of a monohybrid cross to create the dihybrid cross. From these experiments, he determined the phenotypic ratio (9:3:3:1) seen in dihybrid cross for a heterozygous cross.

Through these experiments, he was able to determine the basic law of independent assortment. This law states that traits controlled by different genes are going to be inherited independently of each other. Mendel was able to figure this law out because in his crosses he was able to get all four possible phenotypes.

Expected genotype and phenotype ratios[edit]
The phenotypic ratio of the F2 offspring of the cross is 9:3:3:1, where 9/16 of the F2 individuals possess the dominant phenotype for both traits, and 1/16 are recessive for both traits. This phenotypic ratio only applies to angiosperms or similar sexually reproducing organisms.

According to Mendel's statement, the relationship between alleles of both these loci is complete dominance, meaning if one dominant allele is inherited, the resulting phenotype for that gene will be the dominant phenotype. In the example pictured to the right, the cross of RRYY/rryy parents results in F1 offspring that are heterozygous for both R and Y (RrYy). The following F2 generation results in the expected 9:3:3:1 phenotypic ratio. Another example is listed in the table below and illustrates the process of dihybrid crosses between pea plants with multiple traits and their phenotypic ratio patterns. Dihybrid crosses are easily visualized using a Punnett square of dimensions 16. In these squares, the dominant traits are uppercase, and the recessive traits of the same characteristic are lowercase.


 * In the following case the example of pea plant seed is chosen. The two characteristics being compared are


 * 1) Shape: round or wrinkled
 * 2) colour: yellow or green


 * R (roundness) is dominant and Y (yellow colour of seed) is dominant. This implies that Rr will be a round seed and Yy will be a yellow seed. Only rr will be wrinkled seed and yy will be green seed. This exhibits the idea of complete dominance.

The rules of meiosis, as they apply to the dihybrid, are stated in Mendel's first and second law, which are also known as the Law of Segregation and the Law of Independent Assortment, respectively.

For genes on separate chromosomes, each allele pair showed independent segregation. If the F1 generation produces four identical offspring, the F2 generation, which occurs by crossing the members of the F1 generation, shows a phenotypic (appearance) ratio of 9:3:3:1, where:


 * the 9 represents the proportion of individuals displaying both dominant traits: 1 x RRYY + 2 x RRYy + 2 x RrYY + 4 x RrYy
 * the first 3 represents the individuals displaying the first dominant trait and the second recessive trait: 1 x RRyy + 2 x Rryy
 * the second 3 represents those displaying the first recessive trait and second dominant trait: 1 x rrYY + 2 x rrYy
 * the 1 represents the homozygous, displaying both recessive traits: 1 x rryy
 * The Dihybrid phenotypic ratio= 9:3:3:1
 * The genotypic ratio are: RRYY 1: RRYy 2: RRyy 1: RrYY 2: RrYy 4: Rryy 2: rrYY 1: rrYy 2: rryy 1.

Lead
Dihybrid cross is a cross between two individuals with two observed traits that are controlled by two distinct genes.

The idea of a dihybrid cross came from Gregor Mendel when he observed pea plants that were either yellow or green and either round or wrinkled.

If one of the parents is homozygous dominant for both genes and the other parent is homozygous recessive for both genes, then the offspring will be uniformly heterozygous for both genes and will display the dominant phenotype for both traits.

Self-pollination or crossing of these individuals Crossing of two heterozygous individuals will result in predictable ratios of both genotype and phenotype in the F2 generation offspring. The expected phenotypic ratio of crossing heterozygous parents would be 9:3:3:1[1]. Deviations from these expected ratios may indicate that the two traits are linked or that one or both traits has a non-Mendelian mode of inheritance.

Mendelian History
Gregor Mendel was an Austrian monk who bred peas plants in his monastery garden and compared the offspring to figure out inheritance of traits from 1856-1863 (need to add a source for this found in anther wiki article)[1]. He first started looking at individual traits, but began to look at two distinct traits in the same plant. His first experiment looking at two distinct traits was found by looking at pea color (yellow or green) and pea shape (round or wrinkled)(Still need to rearrange this sentence). He applied the same rules of a monohybrid cross to create the dihybrid cross[1]. From these experiments, he determined the phenotypic ratio (9:3:3:1) seen in dihybrid cross for a heterozygous cross[2].

Through these experiments, he was able to determine the basic law of independent assortment. This law states that traits controlled by different genes are going to be inherited independently of each other[2]. Mendel was able to figure this law out because with his crosses he was able to get all four possible phenotypes.

Expected genotype and phenotype ratios[edit]
The phenotypic ratio of the F2 offspring of the cross is 9:3:3:1, where 9/16 of the F2 individuals possess the dominant phenotype for both traits, and 1/16 are recessive for both traits[1]. This phenotypic ratio only applies to angiosperms or similar sexually reproducing organisms.

According to Mendel's statement, the relationship between alleles of both these loci is complete dominance, meaning if one dominant allele is inherited, the resulting phenotype for that gene will be the dominant phenotype (This is saying the law of dominance. Shorten and say law of dominance. Possibly add this law to the section above)[3]. In the example pictured to the right, the cross of RRYY/rryy parents results in F1 offspring that are heterozygous for both R and Y (RrYy). The following F2 generation results in the expected 9:3:3:1 phenotypic ratio.

Another example is listed in the table below and illustrates the process of dihybrid crosses between pea plants with multiple traits and their phenotypic ratio patterns. Dihybrid crosses are easily visualized using a 4X4 Punnett square of dimensions 16 that results in 16 total possible outcomes. In these squares, the dominant traits are uppercase, and the recessive traits of the same characteristic are lowercase.


 * In the following case the example of pea plant seed is chosen. The two characteristics being compared are


 * 1) Shape: round or wrinkled
 * 2) Colour (Change to color, the american spelling): yellow or green


 * R (roundness) is dominant and Y (yellow colour of seed) is dominant. This implies that Rr will be a round seed and Yy will be a yellow seed. Only rr will be wrinkled seed and yy will be green seed. This exhibits the idea of complete dominance. This section can be taken out and added to the two bullet points listed above.

The rules of meiosis, as they apply to the dihybrid, are stated in Mendel's first and second law, which are also known as the Law of Segregation and the Law of Independent Assortment, respectively[2]. (I do not think that this section needs to be there at all)

For genes on separate chromosomes, each allele pair showed independent segregation. If the F1 generation produces four identical offspring, the F2 generation, which occurs by crossing the members of the F1 generation, shows a phenotypic(appearance) ratio of 9:3:3:1, where: (This section is just a repeat of the section above. I do not think that it is needed, but it helps to separate out the exact ratios and why. I propose deleting the short paragraph above and then moving the bullet points to below the paragraph “According to Mendel's statement…”)


 * the 9 represents the proportion of individuals displaying both dominant traits: 1 x RRYY + 2 x RRYy + 2 x RrYY + 4 x RrYy
 * the first 3 represents the individuals displaying the first dominant trait and the second recessive trait: 1 x RRyy + 2 x Rryy
 * the second 3 represents those displaying the first recessive trait and second dominant trait: 1 x rrYY + 2 x rrYy
 * the 1 represents the homozygous, displaying both recessive traits: 1 x rryy
 * The Dihybrid phenotypic ratio= 9:3:3:1
 * The genotypic ratio are: RRYY 1: RRYy 2: RRyy 1: RrYY 2: RrYy 4: Rryy 2: rrYY 1: rrYy 2: rryy 1.

Lead

Dihybrid cross is a cross between two individuals with two observed traits that are controlled by two distinct genes. Self-pollination or crossing of these heterozygous individuals will result in predictable ratios of both genotype and phenotype in the F2 generation. Deviations from these expected ratios may indicate that the two traits are linked or that one or both traits has a non-Mendelian mode of inheritance. (Need to add sentence about Mendel)

Mendelian History
In 1856-1863, Gregor Mendel was an Austrian monk who bred peas plants in his monastery garden and compared the offspring to determine the inheritance of traits. He first started looking at individual traits, but began to look at two distinct traits in the same plant. The first two distinct traits he looked at was pea color (yellow or green) and pea shape (round or wrinkled). He applied the same rules of a monohybrid cross to create the dihybrid cross. From these experiments, he determined the phenotypic ratio (9:3:3:1) seen in dihybrid cross for a heterozygous cross.

Through these experiments, he was able to determine the basic law of independent assortment. This law states that traits controlled by different genes are going to be inherited independently of each other. Mendel was able to figure this law out because with his crosses he was able to get all four possible phenotypes. Include other laws?

Expected genotype and phenotype ratios[edit]
The phenotypic ratio of the F2 offspring of the cross is 9:3:3:1, where 9/16 of the F2 individuals possess the dominant phenotype for both traits, and 1/16 are recessive for both traits. This phenotypic ratio only applies to angiosperms or similar sexually reproducing organisms.

According to Mendel's statement, the relationship between alleles of both these loci is complete dominance, meaning if one dominant allele is inherited, the resulting phenotype for that gene will be the dominant phenotype. Add law of dominance above and shorten in this section. In the example pictured to the right, the cross of RRYY/rryy parents results in F1 offspring that are heterozygous for both R and Y (RrYy). The following F2 generation results in the expected 9:3:3:1 phenotypic ratio. Do we need this again

Another example is listed in the table below and illustrates the process of dihybrid crosses between pea plants with multiple traits and their phenotypic ratio patterns. Dihybrid crosses are easily visualized using an 4 by 4 Punnett square. In these squares, the dominant traits are uppercase, and the recessive traits of the same characteristic are lowercase.


 * In the following case the example of pea plant seed is chosen. The two characteristics being compared are


 * 1) Shape: round or wrinkled (Round (R) is dominant)
 * 2) color: yellow or green (Yellow (Y) is dominant)


 * This implies that Rr will be a round seed and Yy will be a yellow seed. Only rr will be wrinkled seed and yy will be green seed. This exhibits the idea of complete dominance.

The rules of meiosis, as they apply to the dihybrid, are stated in Mendel's first and second law, which are also known as the Law of Segregation and the Law of Independent Assortment, respectively. Discuss this concept in the history section and not here.

For genes on separate chromosomes, each allele pair showed independent assortment. If the F1 generation produces four identical heterozygous offspring, the F2 generation, which occurs by crossing the members of the F1 generation, shows a phenotypic (appearance) ratio of 9:3:3:1, where:

The expected phenotypic ratio of 9:3:3:1 can be broken down into:


 * the 9 represents the proportion of individuals displaying both dominant traits: 1 x RRYY + 2 x RRYy + 2 x RrYY + 4 x RrYy
 * the first 3 represents the individuals displaying the first dominant trait and the second recessive trait: 1 x RRyy + 2 x Rryy
 * the second 3 represents those displaying the first recessive trait and second dominant trait: 1 x rrYY + 2 x rrYy
 * the 1 represents the homozygous, displaying both recessive traits: 1 x rryy
 * The Dihybrid phenotypic ratio= 9:3:3:1
 * The genotypic ratio are: RRYY 1: RRYy 2: RRyy 1: RrYY 2: RrYy 4: Rryy 2: rrYY 1: rrYy 2: rryy 1.

Add citation for Mendel years and make sure citations are correct

Add picture and caption!