Essential Question How are dominant and recessive sexlinked traits passed onto offspring Sexlinked traits are determined by genes on sexchromosomes Most sexlinked alleles genes are carried on the X chromosome ID: 244721
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Slide1
Sex-Linked Traits
Essential Question: How are dominant and recessive sex-linked traits passed onto offspring?Slide2Slide3
Sex-linked traits are determined by genes on sex-chromosomes.
Most
sex-linked alleles (genes) are carried on the X chromosome. Slide4
Rett
Syndrome is a dominant allele sex-linked trait. A carrier female conceives a child with an unaffected male. What percentage of their daughters will have Rett’s Syndrome?
Rett
syndrome is a neurodevelopmental disorder that affects girls almost exclusively.Slide5
Two of 4 boxes are females (the two on the left). Of the 2
boxes on the left, only 1 has the dominant allele (R). This
means that 1 of 2 females has the diseases. 50%.Slide6
If the
sex-linked trait is
recessive, then males require 1 copy and females require 2 copies.Slide7
Hemophilia is a bleeding disorder in which the blood does not clot.
Hemophilia affects mostly males. Explain to me why mostly males are affected.Slide8
If the sex-linked trait is
dominant then ALL of an affected male’s daughters will have the trait.
Oddly enough, NONE of the an affected male’s SONS will have the disease unless the mother has it. Why?Slide9
X-linked
hypophosphatemia is a dominant trait. If a woman with this disease (carrier) conceives a child with a normal man. What percentage of their daughters will have the disease? What percentage of their sons? 60 seconds…GO!Slide10Slide11
Creating a
pedigree chart. Begin with the parents (P1)Slide12
Extend a line to display the
children (F1)Slide13
Extend a line to display
spouse/mates.Slide14
Extend line to display the
grandchildren (F2).Slide15
Shade in
boxes to display the presence of a trait.Slide16
Full box
= has the trait. Half box = carriers the trait.Slide17
For
autosomal inheritance, males are just as likely as females to have the trait/disease.Slide18
For
autosomal inheritance, males are just as likely as females to have the trait/disease.For a sex-linked (X-linked) inheritance, one gender will be more likely than another to have the disease.
X-linked dominant = more females will have it.
Ex. Rett syndrome, Hypophosphatemia, etc.
X-linked recessive
= more males will have it.
Ex. Baldness, Colorblindness, Hemophilia.