Abstract
The objective of the current experiment is to describe how plants function and pass on the traits. Dark is dominant to wrinkled and Green is dominant to pale green. A statistical approach is used for goodness of fit between observed data and data that are predicted from a hypothesis. Null Hypothesis: The results of the experiment are in agreement with the Mendel’s Laws. Dark is dominant to wrinkled and Green is dominant to pale green. The chi square values that are greater than 3.841 are expected to occur less than 5 percent of the time due to random sampling error. A chi square value of 6.5 in this experiment indicates a higher random sampling error. The null hypothesis is rejected and therefore alternate hypothesis is accepted. Alternate Hypothesis: The results of the experiment are not in agreement with the Mendel’s law of genetics.
Introduction
Mendel conducted his famous experiments of Genetics on garden pea plant Pisum sativum from the year 1856 to 1864 and his work was given title ‘Experiments on Plant Hybridization’ . It was Gregor Mendel who investigated the inheritance of seven different traits in the garden pea and proposed a set of principles to explain the seven characteristics. Mendel carefully selected the characteristics that could be easily differentiated.
Mendel started with the true breeding plants of pea and called them parental generation (P). It was found that when a true breeding plant for one characteristic (TT) was crossed with another true breeding plant for another characteristic (tt), the resultant plant displayed only one characteristic (Tt). When true breeding tall plant was crossed with true breeding dwarf plant, the resultant plants were tall. The first generation of plants obtained from parental generation was called F1 or First Filial generation. Mendel again allowed F1 generation to fertilize and form F2 or second filial generation.
According to Mendel, each trait was composed of two factors now known as genes and was found in two different forms-dominant and recessive. According to Mendel the offspring inherited one factor from each parent and also proposed that each parent had two different forms of a factor and the factors were inherited randomly.
It is now known that the different factors are called genes and the different forms of factors are called alleles. Therefore, the different forms of a gene are called alleles. In the case of pea plant, there are two different alleles for gene height-dwarfness and tallness. The physical description of an individual is called as phenotype and the description of the alleles present in the gene are called genotype. The genotype for tall plants can be TT or Tt, but for dwarf plants can be tt only. A cross that involves the consideration of only one characteristic is called a monohybrid cross.
F1 Tall (Tt) x Tall (Tt)
F2 ¾ Tall (Tt, Tt, TT) ¼ Dwarf (tt)
(Phenotypic Ratio 3:1)
The cross that involves two different traits at the same time was known as a dihybrid cross.
F1 Round Green X Wrinkled Yellow
F2 9/16 Round Yellow, 3/16 Round Green, 3/16 Wrinkled Yellow and 1/16 Wrinkled Green
(Phenotypic Ratio 9:3:3:1)
The objective of the current experiment is to describe how plants function and pass on the traits.
Methods
The materials and methods shall include mathematical calculations, chi-sequence test and sample calculations.
Results
Monohybrid Cross
The phenotypic ratio =2.5: 1 = 3:1
Dihybrid Cross (for stem color and leaf color)
Phenotypic ratio = 9: 3:3:1
Probability =Number of individuals of a given phenotype/Total number of individuals
A statistical approach is used for goodness of fit between observed data and data that are predicted from a hypothesis.
Null Hypothesis: The results of the experiment are in agreement with the Mendel’s Laws. Dark is dominant to wrinkled and Green is dominant to pale green.
Expected phenotypic ratio =9:3:3:1
Expected probability of Round Dark Green = 9/16
Expected probability of Wrinkled Dark Green =3/16
Expected probability of Round Pale Green =3/16
Expected probability of Wrinkled Pale Green =1/16
Expected number of Round Dark Green individuals= 9/16 X1675 = 942
Expected number of Wrinkled Dark Green individuals=3/16 X1675 = 314
Expected number of Round Pale Green individuals =3/16 X 1675 =314
Expected number of Wrinkled Pale Green individuals =1/16 X1675 =105
According to the chi square test = Chi Square = (916-942)2/942 + (332-314)2/314 +(301-314)2/314+(126-105)2/105 = 0.71+ 1.03+0.538+4.2 =6.478
The chi square values that are greater than 3.841 are expected to occur less than 5 percent of the time due to random sampling error. The higher value of chi square indicates an experimental error and the null hypothesis is rejected and therefore alternate hypothesis is accepted.
Alternate Hypothesis: The results of the experiment are not in agreement with the Mendel’s law of genetics.
Discussion
In cross pollinating plants that produce yellow or green pea seeds exclusively, the first generation (F1) always has yellow seeds.
Dihybrid Cross
According to Mendel’s law of dominance, out of a pair of alleles, one is dominant and other is recessive. When one heterozygous parent generation is crossed with another heterozygous parent generation, a ratio of 3:1 is obtained. The results of the current experiment also produce a similar ratio of 3:1 for a monohybrid cross.
According to the Mendel’s Law of Segregation, the alternate versions in the genes are responsible for variations in the inherited characters . For each characteristic, an organism inherits two genes, one from each parent. If the two alleles have contrasting characters one expresses itself and is called dominant and the other one is recessive.
When pure strains of a tall pea plant with round green seeds are crossed with short pea plant with the wrinkled yellow seeds, the first generation has all plants are tall with yellow round seeds. When F1 generation is self-pollinated to form F2 generations mix results are obtained.
The results are indicative of a high random error and therefore inaccurate.
Works Cited
Achiever's Biology. New Delhi: Allied Publishers Private Limited, n.d.
Arora, Sidharth. Excel With Complete Genetics. Golden Bells, 2006. Print.
