_____ is carried by recessive genes and inherited when a child inherits two recessive genes.

• A. Fragile X syndrome
• B. Down syndrome
• C. Cystic fibrosis
• D. Turner's syndrome

Answer: (C)

Verified step by step guidance

1. Begin by understanding the concept of recessive genes. Recessive genes require two copies (one from each parent) for the trait they carry to be expressed in the offspring.
2. Identify the conditions listed in the problem: Fragile X syndrome, Down syndrome, Cystic fibrosis, and Turner's syndrome.
3. Research each condition to determine which are caused by recessive genes. Fragile X syndrome and Down syndrome are not caused by recessive genes; they are linked to chromosomal abnormalities.
4. Understand that Turner's syndrome is a chromosomal disorder affecting females, where one of the X chromosomes is missing or partially missing, not related to recessive genes.
5. Recognize that Cystic fibrosis is a genetic disorder caused by mutations in the CFTR gene, which is inherited in an autosomal recessive manner, meaning it requires two recessive genes for the condition to manifest.