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20 Cards in this Set
- Front
- Back
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Autosomal dominant disease |
Inherited Breast cancer / colon cancer AD Polycystic kidney disease Neurofibromatosis type 1 Huntington's |
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Autosomal recessive diseases |
Sickle cell disease Cystic fibrosis Phenylketonuria Spinal muscular atrophy Congenital adrenal hyperplasia |
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X-linked recessive diseases |
Duchenne muscular dystrophy Becker muscular dystrophy |
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Define 'Knight's move' pattern of inheritance |
Relates to X-linked recessive conditions. Males are affected; there's no male to male transmission; and some related females must be obligate carriers |
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X-linked dominant diseases |
Fragile X syndrome Vit D resistant rickets Incontinentia pigmenti (male lethality) Rett syndrome (male lethality) |
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Give 3 examples of genetic disorders which exhibit genetic anticipation |
Huntington's disease Fragile X syndrome Myotonic dystrophy |
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Give 2 factors which characterise pseudo-dominant inheritance |
Very high carrier frequency Consanguinity |
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Give 6 characteristics of mitchondrial DNA |
Small Circular 16.6kb 37 genes no introns heteroplasmy |
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Give an example of syndrome resulting from mitochondrial DNA gene mutation |
Leigh's disease |
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List 4 examples of atypical inheritance |
Genetic anticipation Gonadal mosaicism Mitochondrial Pseudo-dominant |
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Describe AUTOSOMAL DOMINANT patterns of inheritance |
Affected - heterozygous Each affected has at least one affected parent Seen in every generation M:F roughly equal Variable expressivity - 50:50 chance offspring affected May have incomplete penetrance |
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Describe AUTOSOMAL RECESSIVE patterns of inheritance |
Affected homozygotes Both parents of affected person OBLIGATE CARRIERS Equal frequency and severity males and females Not seen in every generation typically Offspring of affected individuals 25% chance affected Consanguinity inc risk passing on trait |
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Define PENETRANCE |
Frequency with which characteristic controlled by gene expressed in individuals possessing that gene allele |
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Define INCOMPLETE PENETRANCE |
When proportion of people possessing gene do not express in phenotype the trait it controls |
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Define VARIABLE EXPRESSIVITY |
Range of signs and symptoms occur in different people with same genetic condition e.g. mild to severe spectrum. Influenced by presence of modifier gene variants. |
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MODIFIER GENE |
Gene which does not control whether a person possesses a trait but does influence onset, progression and severity of the trait e.g. disease. |
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Explain the concept of 'X-linked inheritance' |
Traits determined by genes located on sex chromosomes. X-linked Dominant: No male to male transmission Always female to male transmission - full penetrance Male to female and female to female transmission > variable expressivity (random v. skewed X-inactivation) X-linked recessive: Males unaffected Both parents of affected females are obligate carriers Full penetrance in females |
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Define GENETIC ANTICIPATION |
Age of onset tends to decrease and severity tends to increase with transmission to successive generations. |
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Define PSEUDOAUTOSOMAL CONDITIONS |
Observed in X-Linked conditions. Tips of p and q arms escape inactivation. Genes at these loci also on Y chromosome. Hence mutations inherited in same way as autosomal gene mutations. |
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Define PSEUDODOMINANT INHERITANCE |
True recessive but displays pseudodominant pattern when frequency of genetic variant in population very high e.g. Gilbert Syndrome |
