Genetics Topics in Depth
Mendelian Genetics
To Pea or Not to Pea: Mendelian GeneticsGregor Mendel (1822–1884), an Austro-Hungarian monk, discovered what is considered to be the very foundation of genetics by growing pea plants in the garde...
Genetic Linkage
Mendel's second law, the law of independent assortment, concerns the random separation of different genes carried on different chromosomes. During meiosis, each chromosome in a homologous pair make...
Modification of Dominance Relationships
As it turns out, Mendel was a lucky man. He picked, partly by accident, characters and corresponding alleles that showed simple relationships between dominance and recessiveness. Often, different a...
Lethal Alleles
There's also another factor that can affect what offspring you get to see, one that can make an allele behave in both a dominant and a recessive manner at the same time: lethality.Some alleles are...
Gene Interactions
Let's take another few steps away from the beauty and simplicity of Mendelian genetics. Kind of the same thing as when you were learning to count, once you had 1 to 100 mastered, they told you ther...
Sex Determination and the Inheritance of Sex Linked Traits
Sex DeterminationIn many organisms sex is determined genetically. Often this is accompanied by chromosomal differences between the sexes. Chromosomes, structures made of proteins and coiled DNA, co...
Quantitative Genetics
Not Everything is Black or White: Quantitative GeneticsMost traits do not fall in discrete, qualitative categories (round or wrinkled, present or absent) but instead have a continuous, seemingly sm...
Extranuclear Genetics
Think Outside the Box: Extranuclear GeneticsDNA is not restricted to the nucleus: it's also found in two cytoplasmic organelles, the mitochondrion and the chloroplast . In most species, the DNA in...
The Chi-Squared Test
Lies, More Lies, and… the χ2 TestDespite the misuse and abuse they get in everyday life, when you're studying genetics, statistics really are helpful, particularly when trying to figure out if y...
Common Mistakes
Mendelian GeneticsA capital letter in a genotype represents a dominant allele; a lower case letter represents a recessive allele. It doesn't really matter what letter you use, just try to pick one...
Test Your Knowledge
Mendelian Genetics Questions1. How do the genotype and phenotype of an organism relate to each other? (The genotype is the genetic constitution of an organism, the phenotype is the physical manifes...
Made From Trees
Allen, G., Carlson, E., Lombardo, P., Micklos, D., Selden, S., & Witkowski, J. A. Image Archive on the American Eugenics Movement, 2010, from http://www.eugenicsarchive.org/eugenics/Aronova-Tiu...