Question

question 18
1 pts
a child is diagnosed with cystic fibrosis. history reveals that the child’s parents are siblings. cystic fibrosis was most likely the result of:
x inactivation.
genomic imprinting.
consanguinity.
obligate carriers.
question 19
1 pts
an aide asks the nurse why people who have neurofibromatosis will show varying degrees of the disease. which genetic principle should the nurse explain to the aide?
penetrance
expressivity
dominance
recessiveness
question 20
1 pts
to express a polygenic trait.
genes must interact with the environment
several genes must act together.
multiple mutations must occur in the same family.
penetrance must occur

Explanation:

Question 18

Cystic fibrosis is an autosomal recessive disorder. Consanguinity (parents being relatives, here siblings) increases the chance of both parents carrying the same recessive allele, leading to the child inheriting two copies. X - inactivation is related to X - linked genes, genomic imprinting involves gene expression based on parental origin, and obligate carriers are those known to carry a recessive allele (not related to consanguinity here).

Expressivity refers to the degree of manifestation of a genetic trait. Neurofibromatosis showing varying degrees of the disease is due to expressivity. Penetrance is about the proportion of individuals with a gene who show the trait, dominance is about allele expression over another, and recessiveness is about allele expression when homozygous (not related to varying degrees of the same trait).

A polygenic trait is determined by the combined effect of multiple genes. Genes interacting with the environment is about gene - environment interaction (not specific to polygenic), multiple mutations in the same family is not the definition of polygenic, and penetrance is about trait manifestation (not related to polygenic trait expression).

Answer:

C. consanguinity

Question 19