40. Criss-cross inheritance is shown by-
(1) Sex linked traits
(2) Sex influenced traits
(3) Sex limited traits
(4) Autosomes
Criss-cross inheritance is shown by sex-linked traits, specifically genes located on the X chromosome. This inheritance pattern involves gene transmission from a father to a daughter and then from that daughter to her son, effectively skipping a generation and crossing sexes.
Explanation of Options
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Sex linked traits: These involve genes located on the sex chromosomes, mainly the X chromosome. In criss-cross inheritance, a male with a sex-linked gene passes it to all his daughters (carriers), who can then pass it to their sons, showing the pattern of inheritance from father to daughter to grandson. Examples include hemophilia and color blindness.
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Sex influenced traits: These are autosomal traits whose expression is influenced by the sex of the individual but are not carried on the sex chromosomes. For example, male-pattern baldness is a sex-influenced trait, expressed differently in males and females due to hormonal variations. These traits do not follow criss-cross inheritance.
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Sex limited traits: These traits are expressed only in one sex even though both sexes may carry the genes. An example is beard growth in males. These are also autosomal and do not show criss-cross inheritance.
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Autosomes: These are the non-sex chromosomes (chromosomes other than X and Y). Genes located on autosomes do not follow criss-cross inheritance as they are inherited independent of sex.
Introduction:
Criss-cross inheritance is a distinctive genetic pattern observed primarily in sex-linked traits. This unique form of inheritance involves the transmission of genes from a father to daughter and then to grandson, highlighting the importance of the X chromosome in genetic diseases like hemophilia and color blindness. Understanding this pattern helps clarify why certain traits skip generations and affects males and females differently.
This article explains why criss-cross inheritance is exclusive to sex-linked traits and distinguishes it from sex-influenced, sex-limited, and autosomal traits.
Criss-cross inheritance occurs because males have one X and one Y chromosome, while females have two X chromosomes. An affected male passes the mutated gene only to his daughters, who become carriers but usually do not show the trait, and these carrier daughters pass it to their sons, who then express the trait due to having only one X chromosome.
Sex-influenced traits depend on hormones and autosomal genes, expressing differently in males and females but not following a criss-cross pattern. Sex-limited traits express in only one sex despite being present in both sexes genetically. Autosomal genes are not tied to sex chromosomes, so their inheritance does not follow the criss-cross pattern.
This clarification helps in genetic counseling, especially for families affected by X-linked disorders, by explaining inheritance risks and patterns through generations.
Criss-cross inheritance is therefore exclusively linked with sex-linked traits, helping explain many sex-specific genetic disease patterns seen in humans and other organisms.
This comprehensive explanation aligns with the question that criss-cross inheritance is shown by sex-linked traits.
