[28] На Х- и Y-хромосомах человека существуют псевдоаутосомные участки, которые содержат аллели одного гена, и между ними может происходить кроссинговер. Одии из таких генов…

To solve the problem, let's go through each part step by step, focusing on genetic inheritance patterns.

Key Information:

1. Inheritance of Traits:

   • Pseudoxanthoma elasticum (pseudoxanthoma elasticum): Inherited through pseudoautosomal regions of X- and Y-chromosomes and can undergo crossover.
   • Excessive hair growth on the middle phalanges (hairy phalanges): Holandric inheritance (Y-linked).

2. Parental Genotypes:

   • Mother: Has pseudoxanthoma elasticum, no excessive hair growth.
     • Pseudoxanthoma elasticum allele: X_P
     • No hair allele: X_h (since it's Y-linked, she can't carry the allele)
   • Father: No pseudoxanthoma elasticum, has excessive hair growth.
     • No pseudoxanthoma allele: X
     • Hair allele: Y_H

3. Child from First Marriage:

   • Daughter: No anomalies. Possible genotype: X_hX

4. Second Marriage:

   • Father: Has pseudoxanthoma elasticum, no excessive hair growth.
     • Pseudoxanthoma allele: X_P
     • No hair allele: Y

Determine Possible Offspring Genotypes:

1. First Marriage:

   • Mother's Possible Gametes: X_P, X
   • Father's Possible Gametes: X, Y_H

   Possible combinations:

   • X_PX (Carrier, no pseudoxanthoma, no hairy phalanges - daughter)
   • X_PY_H (Son with pseudoxanthoma and hairy phalanges)
   • XX (Normal daughter)
   • XY_H (Son with only hairy phalanges)

2. Second Marriage:

   • Mother's Gametes: Assuming she has X_hX
   • Father's Gametes: X_P, Y

   Possible combinations:

   • X_hX_P (Carrier daughter, no symptoms)
   • X_hY (Normal son)
   • XX_P (Carrier daughter, pseudoxanthoma)
   • XY (Normal son)

Analysis:

Potential for Child with Both Disorders from First Marriage:

• Pseudoxanthoma elasticum: X_P inherited from the mother.
• Hairy Phalanges: Y_H inherited from the father.

Thus, a son could inherit both disorders simultaneously (X_PY_H).

Conclusion:

• Genotypes of First Marriage Children:

  • Daughter: X_PX (no symptoms)
  • Possible son with both disorders: X_PY_H

• Genotypes of Second Marriage Children:

  • Carrier daughter with no symptoms: X_hX_P
  • Normal daughters and sons are also possible.

Child with Two Disorders in First Marriage:

• Yes, a son with both pseudoxanthoma elasticum and hairy phalanges can be born due to the inheritance of X_P from the mother and Y_H from the father.

This comprehensive analysis encapsulates the potential genotypic scenarios for the given problem.