Natural selection was Darwin’s brilliant hypothesis, independently conceived by Wallace, that accounts for adaptations, features that appear “designed” to fit organisms to their environment.

TLS Online TPP Program

#Id: 6346

#Unit 8. Inheritance Biology

Z-Linked Characteristics

TLS Online TPP Program

#Id: 6347

#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.

TLS Online TPP Program

#Id: 6348

#Unit 8. Inheritance Biology

EVOLUTION OF THE Y CHROMOSOME

TLS Online TPP Program

#Id: 6349

#Unit 8. Inheritance Biology

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. 

TLS Online TPP Program

#Id: 6350

#Unit 8. Inheritance Biology

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

TLS Online TPP Program

#Id: 6351

#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.