Sex

Relationship between Sex and Heredity

There are three important points to keep clear in the relationship between sex and heredity.

• Sex-limited Traits Refer to traits that are found only in one sex.
• Hen-feathered vs Cock-feathered: Cock-feathering is limited to males .
• Milk production in dairy animals is limited to females (cows).
• Selection for high milk yield is compounded because you have more selective force in the males but it is hard to measure the milk yield in bulls.
  How would you select for high yielding dairy animals?
• Egg production is limited to females.
• How would you select for high yielding chickens?
  Why are there significant differences from the cows?
• There are other obvious sex-limited characters that I will leave to your curiosity.
• Sex-influenced Traits refer to traits that are expressed in both sexes but the mode of expression is different in one sex.
  • Pattern Baldness is the classic example where the trait or gene is dominant in males and recessive in females.
• Sex-linked Traits refer to traits that are on the same chromosomes as the sex determining genes.

• In 1910 Thomas H. Morgan found a white eyed fly that
  exhibited a very interesting pattern of inheritance in
  reciprocal crosses. ....
• The mode of inheritance was in fact very much related to the chromosome theory of inheritance . For the analysis of this trait T.H. Morgan won the Nobel Prize in 1915.
• Sex Linkage in Humans

Sex linkage is the third choice in genetic proposals .
What is first and second?

Here is a completed analysis of the human pedigree for color blindness.

Genetics is no respecter of persons .

Where did the term "Blue Blood" come from?

Testicular feminization relating to insensitivity to androgens

What are the significant differences between males and females?
How can you determine the difference between males and females?

 What is a Barr body?

What is a calico cat ?

X-inactivation

Human sex-linked anhidrotic ectodermal dysplasia (absence of sweat glands).

Why do female cats, humans, and possibly other mammals have one of their chromosomes inactivated?

Hairy Ears is a holandric trait

Text iGenetics by Peter J. Russell

This web site is provided for instruction in Botany and Zoology 342

by Kenneth G. Wilson,
Professor of Botany
Miami University
wilsonkg@muohio.edu