Inheritance

Sex Linked Genes (traits)

  • More genes are located on the X-chromosome than the Y-chromosome

    Female: XX

    Male: XY

Three main sex linked traits

  • DMD- Duchenne muscular dystrophy

  • Colorblindness

  • Hemophilia (A/B)

X-Linked Traits

The gene located on the X-CHROMOSOME

Examples: Hemophilia, colorblindness, DMD

Intermediate Inheritance

  • Some alleles are neither dominant nor ressecive incomplete dominance: one allele is not completely dominant over another

    • Heterozygous condition shows a blend (example: pink)

Codominance

The phenotype for both alleles are clearly expressed

Examples: Chicken feather colors, protein of blood-types

Multiple Alleles

Many genes exists in more than two forms of alleles

Examples: Human blood types, fur color in rabbits

Codominant and Multiple Alleles

  • Gene for blood type has multiple alleles and also displays codominant inheritance

    Phenotypes (blood-types): A, B, AB, O

Polygenic Traits

  • Many traits are produced by the interaction of several genes

    MANY GENES → ONE TRAIT

Examples: Coat color in does, skin-color in humans

  • Traits typically show a wide variety of phenotype

Genes and The Environment

Environmental conditions can affect gene expression. The phenotype of an organism is only partly determined by its genotype

Summary:

Sex-linked genes, located on the X and Y chromosomes, show specific traits such as Duchenne muscular dystrophy (DMD), colorblindness, and hemophilia. Females have two X-chromosomes (XX) while males have one X and one Y (XY). Inheritance patterns include:

  • X-linked traits: Genes on the X chromosome, e.g., hemophilia, colorblindness, DMD.

  • Intermediate inheritance: Involves incomplete dominance where heterozygous conditions result in a blend, such as pink flowers.

  • Codominance: Both alleles expressed, e.g., chicken feather colors and blood types.

  • Multiple alleles: Genes may have more than two alleles, as seen in human blood types.

  • Polygenic traits: Traits influenced by multiple genes, e.g., skin color and coat color.
    Lastly, environmental factors also impact gene expression, affecting phenotypic outcomes.