HL Bio - Unit 2: Pedigree

Pedigree

A flowchart using symbols to show the inheritance of alleles

Symbols in a pedigree

1. Males: Squares

2. Females: Circles

3. Shaded/crossed square/circle: Affected by the disease

4. Siblings and parents are linked using horizontal lines

5. Incest marriage is shown with a double line

6. Vertical lines are used to show offsprings 

7. Roman numerals are used for generations 

8. arabic numbers are used for the # of individuals in the generation 

Patterns of Inheritance

• Usually every generation has an affected individual

• Unaffected parents cannot have an affected child

• Affected parents can have affected children 

  • Only if both are carriers or have it

Deductive

•  The use of knowledge to reach a conclusion

  • Inferred patterns to determine phenotypes

Inductive

• A conclusion or theory that is worked out through the use of evidence

Discrete Variation

• When there is a set phenotype they can have like eye colours (separate variants with no intermediate between)

  • Not affected by environmental factors

Continuous Variation

• Are variations that are on a scale in a way - like height or skin colour

  • Affected by environmental factors

Polygenic Inheritance

• A trait that is affected by more than one gene

• will turn darker under sunlight exposure with more melanin being made 

Graphing continuous variation

Using a continous bar graph

Graphing discrete variation

• Mean, median and mode

• Box and whisker plots using quartiles and interquartile ranges

  • Outliers > (IQR x 1.5) + Q₃ 

  • OUtliers < Q₁ - (IQR x 1.5)

Normal and Skewed Distribution

• Skewness values for a normal distribution are close to zero, if the skewness is farther away from 0 (either in the positive or negative direction) then you can conclude that the distribution is skewed.