Segregation and Independent Assortment of Alleles

Mendel's Laws describe how alleles are separated and randomly distributed during gamete formation

Exceptions to Mendel's Laws

Incomplete Dominance

Incomplete dominance is an exception to Mendel's Laws where neither allele is completely dominant over the other, resulting in a blended phenotype

Codominance

Codominance is an exception to Mendel's Laws where both alleles are expressed equally, resulting in a phenotype with both traits

Polygenic Inheritance

Polygenic inheritance is an exception to Mendel's Laws where multiple genes contribute to a single trait, resulting in a wide range of phenotypes

Difficulties with Mendel's Laws

Mendel faced challenges with certain plants, like hawkweed, that reproduce asexually and do not follow Mendelian inheritance

Determination by Sex Chromosomes

Sex-linked traits are determined by genes located on the sex chromosomes, X and Y

Inheritance Patterns

X-Linked Dominant

X-linked dominant traits are expressed in both males and females if they have at least one dominant allele

X-Linked Recessive

X-linked recessive traits are expressed in females only if they have two recessive alleles, while males express the trait with a single recessive allele

Y-Linked

Y-linked traits are inherited only by males and are passed down from father to son

Advancements in Genetics

The study of sex-linked traits has been crucial in advancing our understanding of genetics, with significant contributions from research on model organisms like fruit flies

Human Genetic Disorders

X-Linked Disorders

X-linked traits include a variety of genetic disorders, such as Fragile X syndrome and hemophilia

Y-Linked Disorders

Y-linked traits involve genes like SRY, which is critical for male development

Implications for Diagnosis and Management

Understanding sex-linked inheritance patterns is essential for diagnosing and managing genetic disorders and for studying male-specific phenotypes