Shortcut Methods and Tips for Genetics and Evolution Numericals

Shortcuts for Mendelian Genetics

For monohybrid crosses, use a Punnett square to determine the genotypic and phenotypic ratios of the offspring.
For dihybrid crosses, use a dihybrid Punnett square or the method of probability to determine the expected phenotypic ratios.
Remember the basic Mendelian ratios:
- Monohybrid cross: 3:1 ratio for dominant:recessive phenotypes
- Dihybrid cross: 9:3:3:1 ratio for dominant:dominant:recessive:recessive phenotypes

Tips for Linkage and Crossing Over

Draw a linkage map to visualize the arrangement of genes on a chromosome.
Use recombination frequencies to calculate the map distance between genes.
Remember that crossing over increases genetic diversity by creating new gene combinations.

Tricks for Gene Mapping

Use 3-point test crosses to determine the sequence of genes on a chromosome.
Calculate map distances using the formula: map distance = (recombination frequency/2) x 100.
Construct genetic maps by arranging genes in their correct order based on their map distances.

Quick Tips for Human Genetics

Know the karyotype of a human: 22 pairs of autosomes and 1 pair of sex chromosomes.
Understand the inheritance patterns of genetic disorders, including autosomal dominant, autosomal recessive, X-linked dominant, and X-linked recessive disorders.
Use a pedigree chart to trace the inheritance of a genetic trait in a family.

Handy Hints for Evolution

Use the Hardy-Weinberg equilibrium equation: p^2 + 2pq + q^2 = 1, where p is the frequency of the dominant allele, q is the frequency of the recessive allele, p^2 is the frequency of the homozygous dominant genotype, q^2 is the frequency of the homozygous recessive genotype, and 2pq is the frequency of the heterozygous genotype.
Calculate allele frequencies by counting the number of each allele in a population and dividing by the total number of alleles.
Estimate selection coefficients by comparing the allele frequencies in two different generations.