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Sex Determination and Sex-Linked Traits

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Presentation on theme: "Sex Determination and Sex-Linked Traits"— Presentation transcript:

1 Sex Determination and Sex-Linked Traits
Chapter 4

2 Outline Sex Determination Different Karyotypes sry gene and maleness
Sex Linked Traits Barr Bodies

3 1. Chromosomal Sex determination Systems
XX-XO XX-XY ZZ-ZW Haplodiploidy

4 A closer look at 2 different systems of sex determination

5 2. Genetic Sex Determining Systems
Genic Balance Sex Determination Environmental Sex Determination drosophila Slipper limpet

6 Drosophila: genic balance
Sex chromosome Autosome* complement X:A ratio Phenotype XX and AA 1.0 female Xy and AA 0.5 male XXY and AA XXX and AAA 0.67 intersex * autosome= any non-sex chromosome

7 Human Karyotypes Klinefelter Syndrome Non-disjunction NORMAL
Turner Syndrome

8 Maleness Determination of maleness is due to sry gene of Y chromosome
Expression of gender is more complex than just sry gene. Example: androgen insensitivity Xy genotype Many female characteristics!

9 Sex Linked (X-linked) Traits (3 examples)
Human Color Blindness

10 Sex Linked (X-linked) Traits
White eye Drosophila

11 Pedigree of hemophilia
XhY x XHXh ½ XH ½ Xh ¼ XHXh ¼ XhXh ½ Xh ½ Y ¼ XHY ¼ XhY

12 Barr Bodies & X-Inactivation
What are they? Why does it occur?

13 Number of Barr Bodies in Human Cells

14 X-Inactivation in cats
Tortoiseshell Color

15 Y-Linked Inheritance Few genes on Y chromosomes
Few examples of known Y linked traits to date

16 The End

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