Numerical Based on Genetics and Evolution

1. Mendelian Genetics

• Probability of inheritance: Product rule and sum rule

Example: In a dihybrid cross between pea plants, (RrYy) X (RrYy) Probability of Red Flowered & Tall Plant(R_Y_) = (3/4)(3/4) = 9/16

2. Linkage and Recombination

• Calculating genetic distance: Genetic distance = Recombination Frequency

Example: If the recombination frequency between gene A and gene B is 8%, the genetic distance = 8 m.u

3. Pedigree Analysis

• Identifying modes of inheritance: Look for patterns of inheritance in a family tree.

Example: If a rare genetic disorder affects males more often than females and is passed down from an affected father is likely X-linked recessive.

4. Chromosomal Mutations

• Calculating gene dosage: Count the number of copies of a gene in an individual’s genotype

Example: If a person has a deletion on one copy of chromosome 15, which contains the gene for cystic fibrosis, the gene dosage is 1 (hemizygosity). It may affect their health by increasing the risk of developing cystic fibrosis.

5. Population Genetics

• Calculating allele frequencies: Allele frequency = (Number of individuals with allele) / (Total Number of individuals)

Example: In a population of 1000 individuals, if 400 have brown eyes (homozygous dominant), the allele frequency of the brown eye (B) allele = 0.6.

6. Hardy-Weinberg Equilibrium

• Testing for Hardy-Weinberg equilibrium: Compare genotype frequencies to expected values under Hardy-Weinberg equilibrium

Example: If expected frequencies are AA (0.36), Aa (0.48) and aa (0.16) and the observed frequencies match, the population is in equilibrium. No evolution is happening w.r.t this gene.

7. Evolution and Natural Selection

• Calculating the strength of selection: Selection Coefficient (s) = Change in allele frequency / Generation.

Example: If the frequency of a gene variant increases from 0.20 to 0.40 over 10 generations, s = (0.40-0.20)/10 = 0.02.

8. Molecular Evolution

• Estimating evolutionary distances: Use tools like molecular clocks based on substitutions per site per unit of time.

Example: If two sequences differ by 10% and the mutation rate is 1% per million years, the evolutionary distance = (10/1) = 10 million years

9. Phylogenetic Tree Construction:

• Interpreting cladograms and phylogenies: Look at branching patterns and divergence times.

Example: If humans and chimpanzees share a common ancestor that lived 5 million years ago, they’re estimated to have diverged around 5 million years ago.