Genetics

DNA Polymerase

DNA polymerases are the enzymes that replicate DNA in living cells. They do this by adding individual nucleotides to the 3-prime hydroxl group of a strand of DNA. The process uses a complementary, single strand of DNA as a template.

The energy required to drive the reaction comes from cutting high energy phosphate bonds on the nucleotide-triphosphate's used as the source of the nucleotides needed in the reaction.

Hardy-Weinberg Equilibrium Calculator

The relationship between allele frequencies and genotype frequencies in populations at Hardy-Weinberg Equilibrium is usually described using a trait for which there are two alleles present at the locus of interest.

This calculator demonstrates the application of the Hardy-Weinberg equations to loci with more than two alleles. Visit the genetic drift and selection illustration for more on the Hardy-Weinberg Equilibrium.

Drift and Selection

The Hardy-Weinberg equation describes allele frequencies in populations. It predicts the future genetic structure of a population the way that Punnett Squares predict the results of an individual cross. The equation calculates allele frequencies in non-evolving populations. It is based on the observation that in the absence of evolution, allele frequencies in large randomly breeding populations remain stable from generation to generation.

Punnett Square Calculator

A Punnett Square* shows the genotype*s two individuals can produce when crossed. To draw a square, write all possible allele* combinations one parent can contribute to its gametes across the top of a box and all possible allele combinations from the other parent down the left side. The allele combinations along the top and sides become labels for rows and columns within the square.

Genotype and Phenotype Probabilities

Patterns of genetic inheritance obey the laws of probability. In a monohybrid cross, where the allele*s present in both parents are known, each genotype* shown in a Punnett Square* is equally likely to occur. Since there are four boxes in the square, every offspring produced has a one in four, or 25%, chance of having one of the genotypes shown.

Genotype and phenotype probabilities with a monohybrid cross questions


A plant species has two alleles for seed shape: Flat (F) and round (f). The Flat (F) allele exhibits complete dominance. Click on the Punnett Square showing the combination that could produce offspring with 100% heterozygous genotype.

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