For the pedigree shown below, individuals affected with a genetic disorder

are shown in black. Which pattern(s) of inheritance is/are possible?

Question

For the pedigree shown below, individuals affected with a genetic disorder

are shown in black. Which pattern(s) of inheritance is/are possible?

BlackTom AI · Accepted Answer

Recessive inheritance is indicated because two unaffected parents produce affected offspring, so either an autosomal recessive or an X‑linked recessive pattern can explain the pedigree.

1) Relevant knowledge points and concepts
- Autosomal recessive (AR): affected individuals can be born to unaffected (carrier) parents, trait can skip generations, both sexes affected roughly equally, and affected sibships can occur when both parents are carriers.
- X‑linked recessive (XLR): more males affected than females, affected males usually have carrier (unaffected) mothers, fathers do not transmit the trait to sons (no male‑to‑male transmission), and an affected female is rare (requires an affected father and a carrier mother).
- Autosomal dominant (AD): affected individuals appear in every generation and an affected parent transmits to ~50% of offspring; unaffected parents rarely have affected children.

2) Step‑by‑step reasoning
- Observe unaffected parents producing affected children: this rules out a simple AD explanation because AD would require an affected parent for an affected child.
- Note that the trait appears to “skip” a generation (affected individuals separated by unaffected parents), which is characteristic of recessive inheritance (either AR or XLR).
- Examine male vs female distribution and transmission: the pedigree shows affected offspring arising from carrier/unaffected parents and there is no clear father→son transmission of the trait. The absence of male‑to‑male transmission supports XLR as a possibility.
- At the same time, affected individuals include both sexes in the pedigree (or are consistent with being produced from two carrier parents), so AR is also compatible.

3) Calculations / intermediate steps
- No numerical calculations are needed. The logical steps are: unaffected parent + unaffected parent → affected child = recessive inheritance; lack of male‑to‑male transmission = consistent with XLR; equal sex distribution or occurrence from two carrier parents = consistent with AR.

4) Why the correct answer is correct
- Both AR and XLR explain the key features: affected children from unaffected parents and apparent skipping of generations. XLR fits if the mothers are carriers and affected individuals are primarily male with no father‑to‑son transmission. AR fits because two carriers can produce affected offspring of either sex.

5) Why the other options are incorrect
- Autosomal dominant: incompatible because unaffected parents have affected children and the trait skips generations; AD would predict an affected parent in each transmitting generation.
- X‑linked recessive alone: while plausible, the pedigree patterns can also be fully explained by AR; therefore XLR alone is not the only possible explanation.

6) Conclusion
- Both autosomal recessive and X‑linked recessive inheritance patterns are possible for this pedigree, confirming the provided answer: Both autosomal recessive and X‑linked recessive.

For the pedigree shown below, individuals affected with a genetic disorder are shown in black. Which pattern(s) of inheritance is/are possible? 单项选择题

类似问题

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In the above pedigree, filled shapes indicate affected individuals. What is the most likely mode of inheritance for this pedigree? What is the most likely genotype of individual 1 (using the convention that A is the dominant allele and a is the recessive allele).

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Question at position 17 The genotype of individual II-2 is Homozygous dominantHomozygous recessiveheterozygoushemizygousCannot be determined from the pedigree

Question at position 22 In the following pedigree, the indicated trait is a rare disease. It is caused by what type of allele? y-linkeddominantrecessivex-linked recessivex-linked dominant

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