Biology Tutorials > Genetics and Evolution > Mendel’s Law & Mendelian Genetics

Mendel’s Law & Mendelian Genetics

A chart depicting Mendel's Law of Dominance

A chart depicting Mendel’s Law of Dominance

Reviewed by: Mary Anne Clark, Ph.D.

The previous tutorial, Dominance, has described Gregor Mendel’s law of dominance. In this tutorial, you will learn another Mendel’s law — the principle of segregation.

Mendel’s Law of Segregation

The alleles of a gene exist in pairs but when gametes are formed, the members of each pair pass into different gametes. Thus each gamete contains only one allele of each gene.

Example of a Cross

The following dihybrid cross involves two true-breeding pea plants, where two factors are looked at, the shape of the seed and the color of the seed.

More examples of dihybrid cross here.


Mendel’s work, his laws of segregation and independent assortment, and try to understand what these mean for genetics and inheritance. Credit: Professor Dave Explains


Summary of Mendelian Genetics

The past few pages have elaborated on the work of Gregor Mendel and how his work has paved the way for predicting the characteristics of offspring. However, a degree of randomness is involved, when involving factors such as independent assortment during meiosis and the possibility of genetic mutations (explained in further pages).

In light of this, Mendel’s work allowed us to see that there is a degree of genetic inheritance from parents in offspring though modern biology indicates that more factors come into play to determine the final genotype and phenotype of an organism.

Sticking to the subject of genetics, the next tutorial looks at sex determination via chromosomes X and Y and some of the genetic traits inherited via these two chromosomes.





Print this quiz for your students to answer. The first part is a recall of Gregor Mendel’s principles of heredity. The second part is a multiple-choice test about alleles and sex chromosomes.

Subjects: Genetics & Evolution
Lesson: Mendelian Inheritance
Grades: 9th, 10th, 11th, 12th
Type: Quiz


Understanding Mendel’s Laws: choose the correct word/phrases inside the parenthesis to complete the text.

At fertilization, the union of the sperm cell and the egg cell results in a (zygote/gamete) that contains “unit factors”.
These unit factors are later referred to as (DNAs/genes).
A variant of a gene controlling the same trait is called (a chromosome/an allele).
The variants of a gene for a trait may exist in pairs. By the time that the offspring is capable of producing its own sex cells or gametes, the members of these paired unit factors will (segregate, join).
Then, they assort (independently/dependently) into the newly formed gametes.
These events occurs during (mitosis/meiosis). Each gamete will contain only one member of every paired unit factors.

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Biology Tutorials > Genetics and Evolution > Mendel’s Law & Mendelian Genetics

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