Specified sex-linked and organellar inheritance models
For an X-linked locus without a corresponding Y allele in the standard XX/XY model, an XY individual is hemizygous, and reciprocal crosses can yield different genotype distributions.
Key knowledge
For an X-linked locus without a corresponding Y allele in the standard XX/XY model, an XY individual is hemizygous, and reciprocal crosses can yield different genotype distributions. Nuclear sex-linked transmission must be distinguished from organellar inheritance. Mitochondrial and plastid genomes can undergo vegetative segregation as cells divide; parental contributions vary among lineages. Human mitochondrial inheritance is predominantly maternal, while biparental mitochondrial transmission in budding yeast and biparental plastid transmission in some plants illustrate different models.
Conditions and scope
- The XX/XY model does not cover every sex-chromosome system, pseudoautosomal locus, chromosome complement or genotype-to-phenotype relationship; heterozygotes can show effects under X inactivation or other mechanisms.
- Maternal organellar inheritance is not a universal rule across organisms; a non-Mendelian nuclear phenotype alone does not prove the gene is outside the nucleus.
Sources · 3
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
- Biology 2e, 12.2 X-Linked Traits and Reciprocal Drosophila CrossesMary Ann Clark, Matthew Douglas and Jung Choi — OpenStax, Rice UniversityTextbook chapter
- The Genetic Systems of Mitochondria and Plastids, mitotic segregation and parental transmissionBruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts and Peter Walter — Molecular Biology of the Cell, 4th edition (2002), NIH BookshelfTextbook chapter
- Genetics Glossary, mitochondrial DNA: primarily maternal transmission in mammalsUniversity of California, Davis, Veterinary Genetics LaboratoryTextbook chapter
Evidence and review
Read actual 12.2 locus-absence/hemizygosity and reciprocal-cross bodies, including symptomatic-carrier/X-inactivation qualification; Alberts actual search-accessible mitotic-segregation and maternal/biparental yeast/plant paragraphs (direct browse challenged; primary Bookshelf search returned these full bounded sections). UC Davis actual primarily maternal wording supplies bounded mammalian model. Excluded Alberts claim that non-Mendelian phenotype by itself demonstrates an extranuclear locus, fixed fraction of plants and universal circular organelle chromosomes.
2026-10-10 · Independent AI editorial review: All 115 actual compact claims, hypotheses, equation/variable/unit tables and 251 origin semantic links independently read. All exact author source-binding rows and disclosed extents assessed; targeted original bodies or specifically identified indexed primary passages rechecked below. All retained biology compact records read for combined breadth. Independent AI editorial content and practical common-core inventory review; no human specialist, degree/laboratory proficiency, whole-textbook certification or experimental replication. Receipt: biology-independent-content-inventory-review.1.
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