BIO.8.B
The student is expected to predict possible outcomes of various genetic combinations using monohybrid and dihybrid crosses, including non-Mendelian traits of incomplete dominance, codominance, sex-linked traits, and multiple alleles.
Knowledge and Skills Statement
Science concepts--mechanisms of genetics. The student knows the role of nucleic acids and the principles of inheritance and variation of trait in Mendelian and non-Mendelian genetics.
Further Explanation
While Mendelian genetics, codominance, and incomplete dominance are fairly straightforward, the concepts of multiple alleles and sex-linked traits sometimes cause more confusion.
When talking to students about sex-linked traits, it can be helpful to provide human examples. In humans, sex-linked genes can be recessive or dominant and present on the X or Y chromosome. Common human sex-linked phenotypes include male-pattern baldness, hemophilia, red-green colorblindness, some high blood pressure genes, Duchenne muscular dystrophy, and Fragile X syndrome.
Human leukocyte antigen (HLA) blood type is a common example of multiple alleles. A person's blood type comes from multiple alleles that are codominant. A person with both A and B alleles will have blood type AB. A person with neither A nor B alleles will have type O blood.
It is helpful to consider the fact that a trait can both exhibit codominance and have multiple alleles. But a trait with multiple alleles will not necessarily exhibit codominance such as in organisms that exhibit incomplete dominance or a dominant/recessive pattern.
Supporting Information
Research
Yoosefzadeh Najafabadi, Mohsen, Mohsen Hesami, and Istvan Rajcan. "Unveiling the Mysteries of Non-Mendelian Heredity in Plant Breeding." Plants 12, no. 10 (May 2023): 1956. https://doi.org/10.3390/plants12101956
Summary: There are several breeding cases, such as cytoplasmic inheritance, methylation, epigenetics, hybrid vigor, and loss of heterozygosity (LOH), where Mendelian heredity is not applicable, known as non-Mendelian heredity. In this review, we examine the current understanding of non-Mendelian heredity in plants, including the mechanisms, inheritance patterns, and applications in plant breeding, provide an overview of the various forms of non-Mendelian inheritance (including epigenetic inheritance, cytoplasmic inheritance, hybrid vigor, and LOH), explore insight into the implications of non-Mendelian heredity in plant breeding, and the potential it holds for future research.
Research
Thapa, Persia Carol, Duy Ngoc Do, Ghader Manafiazar, and Younes Miar. "Coat Color Inheritance in American Mink." BMC Genomics 24, no. 1 (May 2023): doi: 10.1186/s12864-023-09348-8.
Summary: Understanding the genetic mechanisms underlying coat color inheritance has always been intriguing, irrespective of the animal species, including the American mink (Neogale vision). Overall, the results suggested that color inheritance was complex and subjected to a high degree of diversity in American mink as the genes responsible for all four colors were found to be heterozygous.