Question 1

Which of the following best describes the inheritance pattern of achondroplasia?

Accepted Answer

Autosomal dominant with complete penetrance

Question 2

A child is born with achondroplasia, but neither parent has the condition. What is the most likely genetic explanation?

Accepted Answer

The child has a de novo mutation in the FGFR3 gene

Question 3

Which factor complicates the interpretation of inheritance patterns in Huntington disease?

Accepted Answer

Delayed age of onset

Question 4

What is the recurrence risk for siblings of a child with a genetic disease caused by a new mutation?

Accepted Answer

Very low, because the mutation occurred de novo

Question 5

Which of the following is a classic example of reduced penetrance?

Accepted Answer

Polydactyly, where some individuals with the mutation do not show extra digits

Question 6

A pedigree shows two children with an autosomal dominant disease, but both parents are clinically normal. What is the most likely explanation?

Accepted Answer

Germline mosaicism in one parent

Question 7

Which term describes a single gene mutation causing multiple, seemingly unrelated phenotypic effects?

Accepted Answer

Pleiotropy

Question 8

Which of the following is an example of locus heterogeneity?

Accepted Answer

Mutations in different genes causing retinitis pigmentosa

Question 9

What is the effect of variable expressivity in a genetic disorder?

Accepted Answer

Affected individuals show symptoms of varying severity

Question 10

Which mechanism can increase the recurrence risk for offspring, even if the parents are clinically unaffected?

Accepted Answer

Germline mosaicism

Question 11

A genetic disorder is present in both infantile and adult forms, caused by different mutations in the same gene. What is this phenomenon called?

Accepted Answer

Allelic heterogeneity

Question 12

Which equation would you use to calculate the probability that a child will inherit an autosomal dominant disease from a parent with germline mosaicism, assuming the mutation is present in 10% of the parent's germ cells?

Accepted Answer

$$P = 0.1$$

Question 13

Which of the following statements about achondroplasia is TRUE?

Accepted Answer

Most cases are due to new mutations

Question 14

If a disease shows reduced penetrance, which of the following is TRUE?

Accepted Answer

Some individuals with the disease-causing genotype will not show symptoms

Question 15

Which factor is most likely to explain why two siblings with the same genetic mutation show different severity of symptoms?

Accepted Answer

Variable expressivity

Question 16

Which of the following is a possible cause of reduced penetrance?

Accepted Answer

Epigenetic regulation

Question 17

A patient with neurofibromatosis type 1 (NF1) shows only mild freckling, while another has multiple tumors and vision problems. What genetic concept does this illustrate?

Accepted Answer

Variable expressivity

Question 18

Which of the following best describes the relationship between penetrance and expressivity?

Accepted Answer

Penetrance refers to the proportion of individuals showing any symptoms, while expressivity refers to the range of symptoms shown

Question 19

Which of the following is an example of pleiotropy?

Accepted Answer

A mutation in CFTR causing both lung and pancreatic symptoms in cystic fibrosis

Question 20

If a genetic disease is caused by mutations in several different genes, what is this phenomenon called?

Accepted Answer

Locus heterogeneity

Factors That Complicate Patterns of Single Gene Inheritance

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