Genetics 1 - Genetics in Medicine: Introduction Flashcards
What is the Importance of Family History?
- Can be critical to make diagnosis
- Provides information about natural history and variability
- Can clarify pattern of inheritance
What is Multifactorial Inheritance?
- More common than single gene disorders
- Abnormal phenotype or abnormality due to more than one gene together with known or unknown environmental factors
In multifactorial inheritance, the risk to relatives can be related to what factors? (5)
- How closely one is related to the affected individual(s)
- Similarity of the shared environment
- Severity of the condition in the affected relative
- The age of onset in the affected family member
- The sex of the affected family member
What are the Characteristics of Autosomal Dominant Inheritance (4)?
- Multiple generations are affected
- Males and females are equally likely to be affected
- Male to male transmission occurs
- Each offspring of an affected parent has a 50% change of being affected and a 50% chance of being unaffected
What does de novo mean?
a genetic mutation that neither parent possessed or transmitted
When do *de novo *mutations often occur?
During spermatogenesis and are associated with advanced paternal age
What are the Characteristics of Autosomal Recessive Inheritance (4)?
- Greatest recurrence risk is among siblings of affected individuals
- Males and females are equally likely to be affected
- If parents are both carriers of mutations int he same recessive gene, each pregnancy has a 25% chance of inheriting both normal genes, a 50% chance of being a carrier, and a 25% chance of inheriting both gene mutations and being affected
- Ethnic background and consanguinity may influence the likelihood of a specific recessive disease
What are Sex-linked genes?
Genes located on the X or Y chromosome
What are Sex-limited traits?
Phenotype can only be expressed in one sex or the other based on inherent differences
What are Sex influenced genes?
One sex more likely to have phenotype (ex. male pattern baldness)
What are the Characteristics of Mitochondrial Inheritance (4)?
- Mitochondria are inherited from the mother
- All offspring of an affected or carrier female are at risk of being affected
- All daughters of an affected carrier female are at risk of transmitting the condition
- Affected males cannot pass the condition to any of their children
What are the Characteristics of X-Linked Recessive Inheritance (5)?
- The incidence of the condition is much higher in males than femalse
- All daughters of affected males will be carriers
- The condition is never transmitted directly from father to son
- Sons of carrier females have a 50% chance of being affected and 50% chance of being unaffected with each pregnancy
- Daughters of carrier females have a 50% chance of being a carrier and a 50% chance of inheriting the normal copy of the gene
What is Variation/variability?
Differences between individuals with a given genotype
What is Penetrance?
The proportion of individuals in a population that expresses a given genotype or allele; expressed as a percentage for the disorder
What is Pleiotropy?
Changes in a single gene give rise to multiple phenotypic effects
What is Genetic heterogeneity?
More than one gene or genetic mechanism gives rise to single or similar phenotype
What does this indicate on a genetic pedigree?
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What does the arrow indicate on a genetic pedigree?
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What does this indicate on a genetic pedigree?
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