Phylogenetic relationships are based on,

a. Plesiomorphic character

b. Apomorphic character

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#Unit 8. Inheritance Biology

Z-Linked Characteristics

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#Unit 8. Inheritance Biology

Y-Linked Characteristics

Y-linked traits—also called holandric traits—exhibit a distinct pattern of inheritance.  These traits are present only in males, because only males possess a Y chromosome, and are always inherited from the father.

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#Unit 8. Inheritance Biology

EVOLUTION OF THE Y CHROMOSOME

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Dosage compensation

Equalization in males and females of the amount of protein produced by X-linked genes.

Each female cell one of the two X chromosome becomes inactive. Which X chromosome is inactivated is random.

The Xist (X inactive specific transcript) gene located on the X chromosome, in required for inactivation. 

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Barr body- Inactivated X chromosome that appears as a condensed, darkly staining structure in most cells of female placental mammals. 

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#Unit 8. Inheritance Biology

Number of Barr bodies

Differential expression of a gene that depends on the sex of the parent that transmitted the gene.