Overdominance the heterozygote has higher fitness than the  fitnesses of the two homozygotes

Underdominance, in which the heterozygote has lower fitness than both homozygotes.

Directional selection leads to fixation of the favored allele and elimination of the other allele, as  long as no other evolutionary forces act on the population.

TLS Online TPP Program

#Id: 9470

#XL - T Zoology

Phosphorylated STAT dissociates spontaneously from the receptor, and two phosphorylated STAT proteins form a homodimer.

TLS Online TPP Program

#Id: 9471

#XL - T Zoology

STAT5 becomes activated in erythroid progenitor cells and induces expression of the protein Bcl-xL.

TLS Online TPP Program

#Id: 9472

#XL - T Zoology

Two mechanisms for terminating cytokine signaling:

1. Short-term regulation: SHP1

2. Long-term regulation: SOCS proteins

TLS Online TPP Program

#Id: 9473

#XL - T Zoology

SHP1 a phosphotyrosine phosphatase, contains:

SH2 domain  & Phosphatase domain

TLS Online TPP Program

#Id: 9474

#XL - T Zoology

SHP1 

Binding of an SH2 domain to a phosphotyrosine in the activated receptor unmasks its phosphatase catalytic site

TLS Online TPP Program

#Id: 9475

#XL - T Zoology

SHP1 causes removal of the phosphate from tyrosine in the activation loop of JAK2 & inactivates the JAK kinase.