Chapter 12
Mendelian Genetics
![Punnett Squares](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10772.jpg)
A Punnett square displays the possible genotypes offspring can inherit from two parental genotypes. If a trait’s inheritance pattern (e.g.,…
![Monohybrid Crosses](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10773.jpg)
In the 1850s and 1860s, Gregor Mendel investigated inheritance by performing monohybrid crosses in pea plants. He crossed two plants that were…
![Trihybrid Crosses](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/11969.jpg)
Some of Mendel’s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A trihybrid cross is a…
![Law of Independent Assortment](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10979.jpg)
While Mendel’s Law of Segregation states that the two alleles for one gene are separated into different gametes, a different question of how…
![Pedigree Analysis](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10775.jpg)
A pedigree is a diagram displaying a family’s history of a trait. Analyzing pedigrees can reveal (1) whether a trait is dominant or…
![Incomplete Dominance](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/11974.jpg)
Gregor Mendel's work (1822 - 1884) was primarily focused on pea plants. Through his initial experiments, he determined that every gene in a…
![Polygenic Traits](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10778.jpg)
When more than one gene is responsible for a given phenotype, the trait is considered polygenic. Human height is a polygenic trait. Studies have…
![Background and Environment Affect Phenotype](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/11977.jpg)
Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as…
![The Y Chromosome Determines Maleness](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/11979.jpg)
The Y chromosome is a sex chromosome found in several vertebrates and mammals, including humans. In addition to 22 pairs of autosomes, the human…
![The Ratio of X Chromosome to Autosomes](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/11980.jpg)
In most organisms, sex is determined by the ratio of X and Y chromosomes. However, in some organisms, such as Drosophila and C.elegans, sex is…
![Sex-linked Disorders](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10981.jpg)
Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in…
![Dosage Compensation](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/11983.jpg)
In animals, gender is determined by the number and type of sex chromosome. For example, human females have two X chromosomes, and males have one X…
![Multiple Allele Traits](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10777.jpg)
Multiple allelism describes genes that exist in three or more allelic forms. Although diploid organisms, like humans, normally possess only two…
![Blood Types](https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/11985.jpg)
Human blood is classified into different types based on the presence of antigens on the red blood cell's surface and antibodies in the plasma.…
![Shifting Zebrafish Lethal Skeletal Mutant Penetrance by Progeny Testing](https://cloudfront.jove.com/files/thumbs/56200_t.png)
Zebrafish mutant phenotypes are often incompletely penetrant, only manifesting in some mutants. Interesting phenotypes that inconsistently appear can…
![Protocol for Assessing the Relative Effects of Environment and Genetics on Antler and Body Growth for a Long-lived Cervid](https://cloudfront.jove.com/files/thumbs/56059_t.png)
Cervid phenotype can be placed into one of two categories: efficiency, which promotes survival over extravagant morphometric growth, and luxury,…