Inheritance Patterns - Terms

Question 1

Allelic heterogeneity

Answer 1

Different mutations within the same gene resulting in the same clinical condition.

Question 2

Consanguinity

Answer 2

Reproductive union between 2 relatives.

Question 3

Autozygosity

Answer 3

Inheritance of same altered allele through 2 branches of the same family.

Question 4

Penetrance

Answer 4

Percentage of individuals with a specific genotype showing expected phenotype (increases with age).

Question 5

Expressivity

Answer 5

Range of phenotypes expressed by a specific genotype.

Variable expression as not everyone with same genetic variants have the same symptoms/severity.

Question 6

Recurrence risk

Answer 6

Likelihood that hereditary trait present in one family member will occur again in another.

Question 7

New mutation

Answer 7

De novo mutation.

Question 8

Anticipation

Answer 8

Genetic disorders affect successive generations earlier/more severely, usually due to expansion of unstable triplet repeat sequences.

Question 9

Somatic mosaicism

Answer 9

Genetic fault present in only some tissues in the body.

Question 10

Gonadal mosaicism

Answer 10

Genetic fault present in gonadal tissue.

Question 11

Late - onset

Answer 11

Condition that does not manifest at birth, usually adult - onset.

Question 12

Sex - limited

Answer 12

Condition inherited in AD pattern that seems to affect one sex.

Question 13

Predictive testing

Answer 13

Testing for a condition in a pre - symptomatic individual to predict their chance of developing a condition.

Question 14

Lyonisation

Answer 14

In early embryogenesis, one of the X chromosomes in females are inactivated.

Question 15

Homoplasmy

Answer 15

A eukaryotic cell whose copies of mitochondrial DNA are all identical.

Question 16

Heteroplasmy

Answer 16

There are different copies of mitochondrial DNA in each cell.

Question 17

Locus heterogeneity

Answer 17

Clinical condition can be caused by a mutation in any of one of two genes.

Question 18

Autosomal recessive

Answer 18

Carrier parents have no health problems.
1/4 offspring risk.
Healthy siblings = 2/3 chance of being carriers.
More common in consanguineous unions.
Present in single generation.

Question 19

Autosomal dominant

Answer 19

Male and female affected in equal proportions.
Affected individuals in multiple generations.
Transmission by both sexes to both sexes.

Question 20

X - linked

Answer 20

Usually only males affected.
Usually transmitted through unaffected females.
No male to male transmission.