Mendelian Genetics

MENDEL`S PRINCIPLES OF GENETICS

1.0 INTRODUCTION:
1.1 BACKGROUND

Gregor Mendel, who is now considered as founder of classical genetics, ( Elrod S. & Stansfield w,2010), conducted a series of experiments using garden pea plants, his aim was to find a way of explaining to his fellow scientists who believed the blending theory which had been proposed earlier by Wiseman, that heredity involved the interaction of discrete separable factors (now known as genes)
After a statistical analysis of the results of his experiment, Mendel came up with two Laws of Genetics, The first law called the law of segregation which states that there are pairs of particulate factors which control each trait and they segregate during gamete formation and then come together randomly at fertilization. The second Law, the law of independent assortment states that the inheritance of a certain gene is not affected by another gene on another chromosome. This current experiment is a replica of Mendel’s and it will show how his ideas still apply to nowadays phenomena.
1.2 OBJECTIVES:
The objectives of the experiment are:
• To demonstrate how genes interact with each other to produce different appearances (phenotypes)
• To relate Mendel’s laws of genetics to our current experiment using, red and striped beans respectively.
• To apply statistics to our biological experiment i.e. using Chi-Square Technique

2.0 Materials and Methods
Two containers each had an equal number of red or striped beans were provided on the bench in the laboratory. Each container represented a parent and gametes were formed from these parents. Forty beans were selected randomly from each of the parent container (10 beans remained in each container) and the beans were placed in corresponded spaces on the bench. These spaces represented gametes. The number of beans of each color taken from each container was recorded. Without looking, one bean at a time from each of the gamete spaces were taken and paired into the zygote space until all the beans were paired. The genotypes in the zygote space were counted and the number of each genotype was recorded. (Red was dominant over Stripped)

3.0 RESULTS

3.1 Table: Showing the number of red and stripped beans from each container
PHENOTYPE CONTAINER A CONTAINER B
Red 21 16
Stripped 19 24
Total 40 40

3.2 Table: Showing the number of beans of different phenotypes after paired at the group.
GROUP RED MIXED STRIPPED
1 9 22 9

Phenotypical ratio genotypical ratio
9+22=31 (red beans): 9 = (stripped beans) 9 (red beans): 22(mixed beans):9(stripped beans)
31:9 9:22:9
3.44:1 1:2.44:1 (Since in the experiment red was dominant over stripped, then the combination of red and stripped ended up having a red phenotype.)

3.3 Table: Class Cumulative Data after paired Red Mixed Stripped
Total CCD 166 327 147

Total CCD of Red, mixed and stripped =166+324+147 =640
FROM THE CLASS CUMULATIVE DATA
Phenotype Ratio Genotype ratio
Red+ mixed: Stripped Red: mixed: Stripped
166+324:147 166:324:147
490:147 1.12:2.20:1
3.33:1

3.4 Table: showing the genotypes of beans in punnet square according to Mendelian Monohybrid ratio
R = Red r =Stripped Gametes R r
R RR Rr
R Rr rr

F2 3 Red: 1 Stripped 3: 1 (Mendelian Monohybrid ratio)

3.5 Table: Showing the Chi Square Calculation of Class Cumulative Data χ2= ∑(O -E)2/E
Expected results : Red 3/4×640 = 480 : Stripped 1/4×640 = 160 CLASS O E (O-E) (O-E)2 (O-E)2/E
RED 490 480 10 100 0.20833
STRIPPED 147 160 13 169 1.05625 ∑= χ2=1.2645

Degree of freedom = number of Classes – 1 =2-1=1
The probability value on the Chi Square test distribution results was =0.20≈ (30%)
4.0 DISCUSSION
On the chi-square test distribution results showed that there was a probability amounting to about 30% that the diffrection of the observed results was due to chance alone. However in real biological scenario the combination of genes alone cannot determine the appearance (phenotype) of the offspring but the environment in which the combination happens also contribute to the phenotype of the offspring. 4.1 CONCLUSION
Elrod and Stansfied (2010) mention that, if the p value is greater than 0.05, the results are accepted and if the p value calculated on the Chi-Square is less than 0.05, the hypothesis is rejected. Since p> 0.05, and also the results from class cumulative data phenotype ratio was 3.33:1 close to the expected results of Mendelian phenotype ratio of 3:1. Then the hypothesis is accepted.

5.0 REFERENCE
Elrod S. & Stansfield w. (2010): Schaums outlines- Genetics ( 5th edition) p.41. Mc Graw . New York

6.0 Bibliography
Hartl, D.L. & Jones, E.W (1998) Genetics principles & analyzing (4th edition), Jones and Bartlett Publishers, Toronto, Canada. Brooker R.J (2009): Genetics analysis & Principles (3rd edition) P.23 Mc Graw. New York.

Bibliography: Hartl, D.L. & Jones, E.W (1998) Genetics principles & analyzing (4th edition), Jones and Bartlett Publishers, Toronto, Canada. Brooker R.J (2009): Genetics analysis & Principles (3rd edition) P.23 Mc Graw. New York.