Lecture 13

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Which of the following is the major cause of most cases of achondroplasia?

New mutations (correct)

Reduced penetrance

Germline mosaicism

Delayed age of onset

What is the frequency of achondroplasia in live births?

1 in 10,000

1 in 100,000

1 in 1000

1 in 25,000 (correct)

Which specific mutations in the FGFR3 gene are responsible for achondroplasia?

1138G>A and 1138G>T

1138A>G and 1138C>G

1138G>A and 1138G>C (correct)

1138A>T and 1138C>T

When do new mutations in the FGFR3 gene occur for achondroplasia?

During sperm formation in males Signup and view all the answers

What is germline mosaicism?

When all of the parents' germline cells have a disease mutation Signup and view all the answers

How is germline mosaicism suspected?

When unaffected parents have two or more affected children with an autosomal dominant disease Signup and view all the answers

What is the definition of penetrance?

The probability that a mutant allele will have any phenotypic expression Signup and view all the answers

In which type of diseases does penetrance mostly refer to?

Autosomal dominant diseases Signup and view all the answers

What is reduced penetrance?

When a person shows no disease phenotype despite having the mutation Signup and view all the answers

Can penetrance be variable?

Yes, it can vary between individuals with the same mutation Signup and view all the answers

Which of the following accurately describes reduced penetrance?

Reduced penetrance explains why seemingly unaffected parents have children with a phenotype. Signup and view all the answers

What is the difference between reduced penetrance and variable expressivity?

Reduced penetrance explains why seemingly unaffected parents have children with a phenotype, while variable expressivity is the degree to which trait expression differs among individuals with the same genotype. Signup and view all the answers

Which disease has complete penetrance but variable expressivity?

Neurofibromatosis type 1 (NF1) Signup and view all the answers

What is the diagnostic criteria for NF1?

All of the above Signup and view all the answers

What is pleiotropy?

The occurrence of mutations in different genes causing the same or similar phenotypes. Signup and view all the answers

What is the difference between locus and allelic heterogeneity?

Locus refers to how the same or similar phenotype can be caused by mutations in different genes, while allelic heterogeneity refers to different mutations at the same locus leading to the same or very similar phenotypes. Signup and view all the answers