24 Questions
Why do some communities/ethnic groups have different risk of inherited genetic disorders than the general population?
Due to founder effect and reduction in genetic variation caused by migration or isolation of a small number of endogamous individuals from a large population
What is a common characteristic of groups practicing extensive endogamy?
Conscious choice to preserve cultural/religious identity
What is the Ellis van Creveld Syndrome commonly observed in the Pennsylvania Amish community characterized by?
Short stature, polydactyly, abnormality of nails and dentition, cardiac defects
What is the allele frequency of Ellis van Creveld Syndrome in the Pennsylvania Amish community?
7%
Which of the following is the most likely cause for the increased frequency of a mutated allele for FANCC in the endogamous Ashkenazi Jewish population in America?
It is likely that the founder population of immigrating Ashkenazi Jews had a higher frequency of this mutation than the general population
What is the most appropriate method for determining if individuals/couples are heterozygous (Aa) for cystic fibrosis with a view to planning pregnancy?
Easier way to test – blood spot test – blood level of immuno reactive tripsinogen IRT
What is a key consideration for population screening of genetic conditions?
Something that is a useful diagnostic test is not necessarily a good population screening test
What is cystic fibrosis in terms of inheritance pattern?
Autosomal recessive condition
What is the main purpose of screening newborns for genetic conditions?
To provide early detection and intervention
What does the term 'Frame Shift Mutation' refer to?
A mutation that puts the trinucleotide sequences that code for an amino acid out of order
What is the key factor in defining a discrete population for purposes of genetics?
Mating patterns
What is a potential consequence of the Founder Effect?
High frequency of a specific allele variant in a specific population
What is the founder effect?
A phenomenon where a small group of related people establishes a new population, leading to a limited gene pool
What is the main cause of Fanconi Aplastic Anaemia (FA)?
Autosomal recessive genetic variants
What is the role of the FA pathway?
Fixing DNA damage during DNA replication
Why do Ashkenazi Jews have a relatively high incidence of inherited genetic diseases?
Genetic bottleneck and endogamy
What led to a 90% reduction in Tay-Sachs disease births in North America between the 1970s and 1990s?
Carrier screening
What is the cause of Cystic Fibrosis?
Mutations in the CFTR gene
What is the prevalence of Fanconi Aplastic Anaemia (FA)?
1 to 5 per million
What is the main method to reduce disease births in specific populations?
Carrier screening
What is the primary factor contributing to the high incidence of inherited genetic diseases in the Ashkenazi Jewish population?
Genetic bottleneck and endogamy
What is the primary cause of genetic dilution of the founder effect?
Exogamy (marrying unrelated people)
How does the prevalence of the p.F508del mutation in Cystic Fibrosis vary across populations?
88% in Denmark, 50% in Italy, and about 30% in Turkey
What is the role of endogamy in the prevalence of inherited genetic diseases?
It increases the likelihood of genetic diseases due to limited gene pools
Study Notes
Founder Effects and Genetic Diseases in Specific Populations
- Founder effect occurs when a relatively discrete breeding sub-population (endogamy) derives from a small group of related people (founders)
- Exogamy (marrying unrelated people) dilutes or diminishes the founder effect
- Fanconi Aplastic Anaemia (FA) is a rare genetic syndrome characterized by short stature, various congenital abnormalities, bone marrow failure, and cancer predisposition
- FA is autosomal recessive, with at least 15 genetic variants associated with distinct disease profiles
- The FA pathway is responsible for fixing DNA damage during DNA replication, and about 20% of homozygotes develop cancer
- The overall prevalence of FA is 1 to 5 per million, with carrier frequencies varying across populations
- Ashkenazi Jews have a relatively high incidence of inherited genetic diseases due to a genetic bottleneck and endogamy
- The current Ashkenazi Jewish population in the US is derived from a limited number of founders with extensive intermarriage
- Carrier screening for Tay-Sachs disease in North America resulted in a 90% reduction in disease births between the 1970s and 1990s
- Each screening program needs to be appraised for viability, effectiveness, and appropriateness in each target population
- Cystic Fibrosis is caused by mutations in the CFTR gene and has a wide range of manifestations, affecting multiple organs
- The most common mutation in Cystic Fibrosis is p.F508del, with varying frequencies across different populations, such as 88% in Denmark, 50% in Italy, and about 30% in Turkey
Test your knowledge of founder effects and genetic diseases in specific populations with this quiz. Explore the impact of endogamy, the prevalence of rare genetic syndromes like Fanconi Aplastic Anaemia, and the genetic variations associated with diseases such as Tay-Sachs and Cystic Fibrosis. Understand the importance of carrier screening and the implications of genetic bottlenecks in populations like Ashkenazi Jews.
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