The following question refers to the figure of a family's pedigree chart, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle.

What is the likelihood that a future child of IV-3 and IV-4 will have the trait?

Question

The following question refers to the figure of a family's pedigree chart, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle.

What is the likelihood that a future child of IV-3 and IV-4 will have the trait?

BlackTom AI · Accepted Answer

The question asks about the likelihood that a future child of IV-3 and IV-4 will have the dominant trait W, given the pedigree.
Option analysis:
- 0%: If both IV-3 and IV-4 are unaffected individuals in a family where W is dominant, each unaffected person must have genotype ww (no W allele). When two ww individuals mate, every child must inherit a w allele from each parent, resulting in ww for all offspring. Therefore, the chance of their child being affected (having W) is 0%. This reasoning hinges on the assumption from the pedigree that IV-3 and IV-4 are not expressing the W phenotype.
- 25%: This would be the typical Mendelian risk for a cross between two heterozygotes (Ww x Ww) producing offspring with genotype WW, Ww, or ww in a 1:2:1 ratio. However, this requires both parents to be carriers (Ww). If either parent is ww (unaffected with no W allele), a 25% risk would not apply because ww cannot contribute a W allele.
- 75%: This option is not consistent with standard inheritance patterns for a single dominant allele. A 75% risk would imply that three of four possible outcomes involve the trait, which doesn’t align with simple dominant-recessive inheritance across a single locus unless additional complexities (e.g., incomplete penetrance, multiple genes, or data misinterpretation) are specified, which are not present in the given pedigree.
- 50%: A 50% risk is characteristic of a cross where exactly one parent is heterozygous (Ww) and the other is homozygous recessive (ww). In that case, each child has a 50% chance of inheriting W. However, this requires one parent to be heterozygous and the other to be ww, which contradicts our conclusion that both IV-3 and IV-4 are unaffected and thus ww. Without evidence that one parent carries W while the other does not, this option is unlikely.
- 100%: A 100% risk would occur if both parents were homozygous dominant (WW) or if the trait were obligate in all offspring due to a fixed genotype. The pedigree does not indicate that both IV-3 and IV-4 are WW; moreover, an unaffected pair cannot produce all affected offspring under a simple dominant model. Therefore, this option does not fit the given information.
In summary, given that IV-3 and IV-4 are shown as unaffected in the pedigree, they must both be ww genotypes, and their child must also be ww, yielding 0% probability of the child being affected.

The following question refers to the figure of a family's pedigree chart, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle. What is the likelihood that a future child of IV-3 and IV-4 will have the trait?单项选择题

类似问题

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

What is the most likely mode of heredity for the trait depicted in this pedigree?

This pedigree shows a family where II-1 is affected by an autosomal recessive disorder. Which individuals MUST be heterozygote?

What is the primary purpose of pedigrees in guiding animal breeding decisions?

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).

What is the primary purpose of using pedigrees in animal breeding?

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

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单