Mendel’s law of segregation is explained by

Question

BlackTom AI · Accepted Answer

Alleles for a single trait are carried on corresponding positions of homologous chromosomes, so the physical basis for Mendel’s law of segregation is the behavior of those homologs during meiosis.

Relevant concepts:
- Alleles = different versions of a gene located at the same locus on homologous chromosomes.
- Meiosis I (anaphase I) separates homologous chromosome pairs so each daughter cell receives one chromosome of each pair.
- Mendel’s law of segregation states that the two alleles for a trait separate into different gametes, so each gamete carries only one allele.

Step-by-step reasoning:
1. A diploid organism has two homologous chromosomes, one from each parent, carrying two alleles for a gene (for example A and a).
2. During prophase I homologs pair (synapsis) but remain distinct chromatids carrying their respective alleles.
3. In anaphase I the homologous chromosomes are pulled to opposite poles; this physical separation sends one allele to one daughter cell and the other allele to the other daughter cell.
4. After meiosis II and gamete formation, each gamete contains a single chromosome of the pair and therefore only one allele (either A or a).
5. When gametes fuse at fertilization, the allele pairs are reconstituted, producing the Mendelian ratios observed in monohybrid crosses (e.g., 3:1 phenotype in F2).

Why the correct answer is correct:
The option “the separation of homologous chromosomes during meiosis” directly describes the physical event that places alleles into separate gametes, which is exactly what Mendel’s segregation describes.

Why the other choices are incorrect:
- “The independent alignment of different chromosomes during meiosis” describes independent assortment (different law), not segregation of alleles at one locus.
- “The crossing over of homologs during meiosis” causes recombination between linked genes but is not the mechanism that separates allele pairs into different gametes.
- “Both the separation of homologous chromosomes... and the independent alignment...” conflates segregation with independent assortment; segregation specifically refers to separation of homologs/alleles.

Conclusion: The correct answer is “the separation of homologous chromosomes during meiosis.”

Mendel’s law of segregation is explained by单项选择题

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