[BIO] pedigree

• how come recessive traits carried on the X chromosome may be more commonly expressed in males? 


  because they only have one X chromosome, while females would need to inherit two copies of the recessive allele to express the trait
• autosomal dominant

  • no skipping of generations
  • affects males and females equally
• autosomal recessive

  • skips generations
  • affects males and females equally
• X-linked dominant

  • does not skip generations
  • a mutation in one copy of an X-linked gene will result in disease for both males and females
• X-linked recessive

  • skips generations
  • more commonly expressed in males
  • if males inherit a recessive allele for an X-linked trait from their mother, they will express that trait because they don't have another X chromosome to mask the effects of the recessive allele
• Y-linked

  • does not skip generations
  • affects males only
• mitochondrial

  • does not skip generations
  • if the mother is affected, all offspring are affected
• Autosomal recessive traits


  pass from both parents onto their child
• Autosomal dominant traits 


  pass from one parent onto their child