Mendelian Inheritance

Question 0

Autosomal dominant

Answer 0

A pattern of inheritance in which an affected individual has one copy of a mutant gene and one normal gene on a pair of autosomal chromosomes. Ex. Huntington disease

Question 1

Allele

Answer 1

One of the alternative versions of a gene or DNA sequence at a given locus

Question 2

Autosomal recessive

Answer 2

A pattern of inheritance in which an affected individual has two copies of the mutant gene. Ex. Cystic fibrosis

Question 3

Codominant

Answer 3

If both alleles of a pair are expressed in the heterozygous state then the alleles (and or traits determined by them) are codominant

Question 4

Compound heterozygote

Answer 4

an individual or genotype with two different mutant alleles at the same locus

Question 5

Consanguineous

Answer 5

Related by descent from a common ancestor

Question 6

Expressivity

Answer 6

The extent to which a genetic defect is expressed. If there is variable expressivity, the trait may vary in expression from mild to severe but is never completely unexpressed in individuals who have the corresponding genotype. Contrast this topic with that of penetrance

Question 7

Founder effect

Answer 7

A high frequency of a mutant allele in a population founded by a small ancestral group when one or more of the founders was a carrier of the mutant allele

Question 8

Genetic anticipation

Answer 8

The progressively earlier onset and increased severity of certain diseases in successive generations of a family. Anticipation is caused by expansion of the number of unstable repeats within the gene responsible for the disease

Question 9

Genotype

Answer 9

The genetic constitution f of an individual as distinguished from the phenotype. More specifically, the alleles present at one locus

Question 10

Heterozygous

Answer 10

An individual or genotype with identical alleles at a given locus on a pair of homologous chromosomes

Question 11

Homozygous

Answer 11

An individual or genotype with identical alleles at a given locus on a pair of homologous chromosomes

Question 12

Locus

Answer 12

The position occupied by a gene on a chromosome. Different forms of the gene (alleles) may occupy the locus

Question 13

Mutation

Answer 13

Any permanent heritable change in the sequence of genomic DNA

Question 14

Penetrance

Answer 14

The fraction of individuals with a genotype known to cause a disease who have any signs or symptoms of the disease. Contrast with expressivity

Question 15

Phenotype

Answer 15

The observed biochemical, physiological, and morphological characteristics of an individual, as determined by his or her genotype and the environment in which it is expressed. Also, in a more limited sense, the abnormalities resulting from a particular mutant gene

Question 16

Polygenic inheritance

Answer 16

Inheritance determined by many genes at different loci with small additive effects; not to confused with multifactorial inheritance, in which environmental as well as genetic factors may be involved

Question 17

Pro band

Answer 17

The affected family member through whom the family is ascertained

Question 18

Random mating

Answer 18

In a randomly mating population, the frequencies of the various makings between individuals with particular genotypes are determined solely by the frequencies of the alleles concerned

Question 19

X-linked dominant

Answer 19

Genetic inheritance by which a dominant gene is carried on the X chromosome. A gene responsible for a genetic disorder is located on the X chromosome, and only one copy of the allele is sufficient to cause the disorder when inherited from a parent who has the disorder

Question 20

X-linked recessive

Answer 20

Genetic inheritance in which a mutation in a gene on the X chromosome causes the phenotype of the expressed (1) in males (necessarily hemizygous for the gene mutation because they only have one X chromosome) (2) in females (homozygous for the gene mutation: they have one copy of the gene mutation on each of their two X chromosomes)