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Sex-influenced Traits

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Sex-influenced Traits Previously, we learned about sex-linked traits, controlled by sex-chromosomes. (x-linked) We will now discuss sex-influenced traits ... – PowerPoint PPT presentation

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Title: Sex-influenced Traits


1
Sex-influenced Traits
2
  • Previously, we learned about sex-linked traits,
    controlled by sex-chromosomes. (x-linked)
  • We will now discuss sex-influenced traits,
    controlled by autosomal chromosomes

3
What is a sex-influenced trait?
  • A sex-influenced trait is controlled by a pair of
    alleles found on the autosomes. (Not on sex
    chromosomes)
  • Its expression is influenced by gender (presence
    of hormones such as estrogen, progesterone,
    testosterone, etc.).
  • Sex-influenced traits vary in the degree of the
    phenotypic expression.

4
Example Pattern Baldness
  • It can occur in both males and females, but is
    influenced by the hormone testosterone.

5
The combination of alleles lead to different
phenotypic expressions depending on gender.
6
What is the probability that you will be bald if
your father is homozygous and balding, and your
mother is homozygous and not balding?
  • Father BB x Mother BB
  • All offspring are BB
  • If you are male, then you will
    be bald.
  • If you are female, then you will not be bald.

7
Actually, Its not that simple
  • Many human traits are controlled
    by several different alleles and
    environmental factors. These
    traits are
    polygenic, such as
    height. (Actually the man at the
    right is a pituitary
    giant at 79
    due to an uncontrolled amount
    of
    growth hormone)
  • This means that we cannot fully explain pattern
    baldness using sex-influenced inheritance. It is
    not easy to explain that diversity found in
    different ages of onset, as well as the severity
    of baldness.

8
Another Example Singing voice
  • The genotype that causes males to have a tenor
    voice (highest male singing voice), causes
    females to have a contralto voice (the deepest
    female singing voice).
  • The genotype that causes males
    to have deep bass voices, is the
    same genotype that causes females
    to have high soprano voices.

Also
9
Peacock plumage
  • The plumage of a male peacock is highly
    decorated and colored, while the plumage of a
    female peahen is dull by comparison.

10
A variety of peacock feathers
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