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1. Medical Genetics > DEFINITIONS > Flashcards

Flashcards in DEFINITIONS Deck (13)
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1

Define "modifier genes".

Other, unrelated genes which have a small effect on phenotype (i.e. affecting disease severity or penetrance)

2

Define "variable expression" or "variable expressivity".

Autosomal dominant disorders in which affected individuals within the same family are affected by a disease to different extents

3

Define "incomplete penetrance".

When there is a less than 100% chance an individual will have the disease if they have the mutated gene

4

Define "complete penetrance".

When there is a 100% chance that the individual will have the disease if they have the mutated gene

5

Define "gonadal mosaicism".

Presence of both normal and mutated egg/sperm cells in unaffected adults of reproductive age

6

Define "compound heterozygotes".

When the two mutations causing an autosomal recessive disease are not the same mutation (e.g. when different mutations of the same allele can cause disease)

7

Define "manifesting carriers".

Carrier females who present with the disease

8

Define "skewed X inactivation".

When there are more X chromosomes being switched off than there are healthy ones, resulting in manifesting carriers

9

Define "genetic anticipation".

Genetic conditions in which the disease shows increasing severity and earlier onset in successive generations

10

Define "trinucleotide repeat disorders".

Disorders caused by long repeats of a trinucleotide, which often get longer in successive generations

11

Define "pseudo-dominant inheritance".

An autosomal recessive condition with consanguinity or a very high frequency, thus affecting people in more than one generation and appearing as an AD disorder

12

Define "heteroplasmy".

Mitochondrial mutations when, out of the several chromosome copies in mitochondrial DNA, some are mutated and some are normal

13

Define the "threshold effect".

The limit in the balance between normal and mutated mitochondrial chromosomes needed to cause disease