Biostatistics in biology

Why we use biostatistics in biology

Facts should be proven

e.g.

• Chemical A is anticancer drug.

• How to prove it?

Facts should be proven

e.g.

• Chemical A is anticancer drug.

• How to prove it?

• Experimental design

• Experimental factors

• Control

Experimental design

• Measure for a pre-tested parameters such as markers

• Use prop

• Test Analysis ……..etc.

Experimental factors

• All experimental factors should be fixed except the drug

• E.g. Dose dependant

• Different extraction method of the drug

• Different administration of the drug

• Sample size of the experiment

Sample size

• Number of replicates tested

Control

• Positive control

• Negative control

Where is the correct value?

variable R1: 30R2: 26R3: 36R4: 48R5: 50R6: 16R7: 31Mean(Ý) =33.85n=7

Statistical analysis

Statistical analysis

Standard deviation

Degree of freedom =n-1

Biological dataAflatoxin in peanut ( Y)

Y-Ý (Y-Ý)2

30 3.85 14.822

26 7.85 61.622

36

48

50

16

31

Mean(Ý) =33.85

n=7

=

Justify a genetic hypothesisusing chi square test

Chi square test

• X2 =

• Also called ANOVA or X2 test for goodness of fit

Is observed data consistent with hypothesized ones?

Example for chi square test application in genetics

In a cross between smooth and wrinkled pea seeds, you obtained 99

smooth seeds and 45 wrinkled seeds. Determine if the ratio 3:1 is

consistent with this result.

Problem 1

Phenotype Observed number Expected number Deviation from expected number

Wild type 99 108 -9 0.75 Mutant 45 36 +9 2.25 Totals 144 144 0 X2=3

Justify 3:1 ratio

Problem 2

• Do you think the inheritance of the above genetic trait follows the ratio of 1:2:1

Problem 2 answerjustify the ratio 1:2:1

Genotype observed expected O-E

AA 159 159.75 -0.75 0.003

Aa 321 319.5 1.5 0.007

aa 159 159.75 -0.75 0.003

Total 639 0.013

Types of variables

1- Qualitative

2- Quantitative

Arrange your data in a meaningful form

1- Data tabulation

2- Graph

3-Statistical analysis

Use of molecular genetic in genotyping

Genetic analysis

• Analysis of a certain genetic trait is very complicated.

• Researchers need to identify all genes responsible for phenotype determination as well as interacting genes.

• E.g.

• Cell shape genes and mutation induction methodology

Mutation induction to study a genetic trait

• X-ray

• Insertional mutagenesis

• Chemical mutagenesis

Complementation test in gene identification

Results interpretation