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Zorluk: OrtaApplications of Genetics in Medicine and Agriculture

During a pre-marital clinical genetic screening, a medical counselor analyzes the hemoglobin genotypes of a prospective couple. The man is homozygous normal (AAAA), while the woman is a heterozygous carrier (ASAS) for sickle-cell disease. What percentage of their offspring is expected to inherit a genotype that is completely free of the sickle-cell allele (SS)?

  1. A
    25%25\%
  2. 50%50\%Cevap
  3. C
    75%75\%
  4. D
    0%0\%

Cevap

50%50\% of the offspring are expected to be homozygous normal (AAAA) and completely free of the sickle-cell allele.
In genetic inheritance of hemoglobin traits, a homozygous normal individual (AAAA) produces only normal alleles (AA). When crossed with a carrier (ASAS) who produces 50%50\% normal alleles (AA) and 50%50\% mutant alleles (SS), half of the resulting offspring inherit an AA allele from both parents (AAAA). Thus, 50%50\% of the offspring are completely free of the sickle-cell allele.

Adım Adım Çözüm

1
Determine the parental genotypes and gametes produced.
Father (AAAA) produces only AA gametic types (100%100\%). Mother (ASAS) produces AA and SS gametes in equal proportions (50%50\% AA, 50%50\% SS).
According to Mendel's Law of Segregation, alleles segregate during gamete formation.
2
Perform a genetic cross using a Punnett square.
Combining gametes yields: 50%50\% AAAA (homozygous normal) and 50%50\% ASAS (heterozygous carrier).
Random fertilization between father's AA gametes and mother's AA or SS gametes yields equal probabilities for AAAA and ASAS genotypes.
3
Identify the proportion of offspring completely free of the sickle-cell allele (SS).
The AAAA genotype has zero copies of the SS allele, which accounts for 50%50\% of the total offspring.
Only individuals with genotype AAAA are completely free of the SS allele; ASAS individuals carry one copy of the allele.

Anahtar Kavram

Application of Mendelian genetics in medical counseling for hemoglobinopathy prevention
Tahmini Süre:1m 30s
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Konular

Applications of Genetics in Medicine and Agriculture

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