Select the incorrect statement about Down's syndrome.

Options

A. It is caused by non-disjunction of autosomes during oogenesis
B. Late pregnancy in woman might be the cause of Dwon's syndrome
C. Affected individuals exhibit 21st trisomy condition
D. A woman with Down's syndrome always give birth to children with Down's syndrome

Answer

To determine the incorrect statement about Down's syndrome, let's analyze each of the given options step by step.

### Step 1: Understand Down's Syndrome
Down's syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21, leading to a condition known as trisomy 21. This chromosomal abnormality occurs due to nondisjunction during meiosis, which can happen in either the egg or sperm formation.

**Hint:** Remember that Down's syndrome is specifically linked to an extra chromosome 21.

### Step 2: Evaluate the First Statement
The first statement claims that Down's syndrome is caused by the non-destruction of autosomes during oogenesis. This statement is correct because the extra chromosome results from nondisjunction during the formation of gametes.

**Hint:** Consider how chromosomes are supposed to separate during gamete formation.

### Step 3: Evaluate the Second Statement
The second statement suggests that late pregnancy in women might be a cause of Down's syndrome. This is also correct, as advanced maternal age (especially over 35 years) is associated with a higher risk of having a child with Down's syndrome.

**Hint:** Think about how maternal age affects genetic conditions.

### Step 4: Evaluate the Third Statement
The third statement indicates that an individual with Down's syndrome exhibits a 21st trisomy condition. This is true, as individuals with Down's syndrome have three copies of chromosome 21.

**Hint:** Recall the definition of trisomy and how it relates to Down's syndrome.

### Step 5: Evaluate the Fourth Statement
The fourth statement claims that a woman with Down's syndrome always gives birth to children with Down's syndrome. This statement is incorrect. While women with Down's syndrome can have children, they do not always pass on the condition. They can give birth to healthy individuals as well.

**Hint:** Consider the fertility of individuals with Down's syndrome and the genetic variability in offspring.

### Conclusion
Based on the evaluations, the incorrect statement about Down's syndrome is: "A woman with Down syndrome always gives birth to children with Down syndrome."

### Final Answer
The incorrect statement about Down's syndrome is: **"A woman with Down syndrome always gives birth to children with Down syndrome."**