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The structural variations of hemoglobin beta chains in three groups of mice developed inChina

inbred strains SMMC/B（abbreviated as B）

SMMC/C（as C）

and a noninbred parentalstock

Kunming（as K）

have been investigated.Dissociation analysis of beta c chains showed that B

C and Ksingle mice have only one kind of beta chain attributed to Hbb

B

Hbb

c

and Hbb

Ksingle

genotypes

each coding for only one unique amino acid sequence.The genotype of Kpair group isattributed to Hbb

Kpair

(i.e.Hbb

Kmaj

/Hbb

Kmin

).This fact indicates that the Hbb

Kpair

allele is composedof two linked genes

coding for structurally different beta chains

beta Kmaj and beta Kmin.As aconsequence of inbreeding and possible natural selection

the genetic fixation of Hbb

single

in the Band C strains and the elutriation of both Hbb

Ksingle

and Hbb

Kmaj

/Hbb

Kmin

in the K stock are dis-cussed.