Heredity influenced by sex

There are characters determined by genes that are not found in the sex chromosomes, but in the autosomes, but whose manifestation depends on the sex of the individual, behaving differently if they are found in males or females. Their inheritance is said to be influenced by sex. The different behavior of these genes is usually due to the effect of male hormones.

The most common examples are:

• Baldness in humans: The allele that determines baldness is dominant in men, but recessive in women. The heterozygous person will be bald, if he is a man, or with hair, if he is a woman:
  • Genotype CC: bald men and bald women.
  • Genotype Cc: bald men, normal women.
  • Genotype cc: normal men and women.
• Antlers in sheep: Like the gene that determines baldness in humans, females have to be homozygous  to have horns.
  
• Index and ring finger length:
  • In men, the dominant gene determines that the index finger is shorter than the ring finger. The recessive, that the index is longer.
  • In women, the dominant gene determines that the index finger is longer than the ring finger. The recessive, that the index is shorter.

Genetic problems: Heredity influenced by sex. Solved exercises.