Genetics pedigree problems | PPT - Free Printable

To determine the pattern of inheritance for the trait shown in the pedigree, let's analyze the image step by step:

Key Observations from the Pedigree:

1. Affected Individuals:
- The red circles represent affected individuals.
- There are two affected individuals: one in the first generation (parent) and one in the third generation (child).

2. Unaffected Individuals:
- All other individuals in the pedigree are represented by white circles, indicating they are unaffected.

3. Generational Pattern:
- The affected individual in the first generation is a female (mother).
- The affected individual in the third generation is a male (son).

4. Transmission:
- The affected trait skips a generation (from the first to the second generation) and reappears in the third generation.

Analysis of Inheritance Patterns:

#### 1. Autosomal Dominant Inheritance:
- If the trait were autosomal dominant, we would expect at least one parent of an affected individual to also be affected. However, the father of the affected individual in the third generation is unaffected, which rules out autosomal dominant inheritance.

#### 2. Autosomal Recessive Inheritance:
- For an autosomal recessive trait, both parents must be carriers (heterozygous) to produce an affected offspring (homozygous recessive). Since neither parent of the affected individual in the third generation is affected, this suggests that both parents could be carriers. This is consistent with autosomal recessive inheritance.

#### 3. X-Linked Dominant Inheritance:
- If the trait were X-linked dominant, we would expect the mother of an affected male to also be affected. However, the mother of the affected male in the third generation is unaffected, which rules out X-linked dominant inheritance.

#### 4. X-Linked Recessive Inheritance:
- For an X-linked recessive trait, males are more likely to be affected because they have only one X chromosome. Females can be carriers but not necessarily affected unless they inherit two copies of the recessive allele. The fact that the affected individual in the third generation is male and the mother is unaffected is consistent with X-linked recessive inheritance.

#### 5. Y-Linked Inheritance:
- Y-linked traits are passed from father to son. Since the affected individual in the third generation does not have an affected father, this rules out Y-linked inheritance.

Conclusion:

The pattern of inheritance in this pedigree is most consistent with X-linked recessive inheritance. Here’s why:
- The affected individual in the third generation is male.
- The mother of the affected male is unaffected but could be a carrier.
- The trait skips a generation, which is typical for X-linked recessive traits.

Final Answer:

$$
\boxed{\text{X-linked recessive}}
$$