An abnormal human male phenotype involving an extra X-chromosome (XXY) is a case of:
Correct answer: B. Klinefelter's syndrome
- A. Edward's syndrome
- B. Klinefelter's syndrome
- C. Intersex
- D. Down's syndrome
Explanation
Klinefelter's syndrome is caused by the presence of an extra X chromosome in males (XXY). This chromosomal abnormality leads to various developmental issues and is specifically a sex chromosomal disorder. Edwards syndrome, also known as Trisomy 18, involves an extra chromosome 18 and is unrelated to sex chromosomes. Intersex refers to a variety of conditions involving atypical development of physical sex characteristics, not necessarily linked to an XXY chromosomal pattern. Down syndrome, or Trisomy 21, involves an extra chromosome 21 and affects autosomes, not sex chromosomes. Therefore, the correct answer is Klinefelter's syndrome, which is directly related to the presence of an extra X chromosome in males.
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About Inheritance
Mendel's laws explain segregation, independent assortment and the prediction of genetic ratios using alleles, genotypes and phenotypes. The chapter also covers linked genes, recombination and crossing over during meiosis, then applies pedigree reasoning to X-linked recessive traits, which show different inheritance patterns in males and females.
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