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Lethal genes are(A) recessive homozygous(B) recessive heterozygous(C) dominant heterozygous(D) codominant |
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Answer» (A) recessive homozygous The disease sickle-cell anaemia is caused by a gene HbS which is recessive. A marriage between two carriers of sickle-cell anaemia (HbA HbS) will produce – normal children with genotype (HbAHbA), sickle cell carriers with genotype (HbAHbS) and sickle-cell anaemic with genotype HbSHbS . Sickle-cell anaemic dies leaving behind carriers and normal. Thus, the gene for sickle-cell anaemia (recessive gene) is lethal in homozygous condition. |
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