Probability and Pedigrees in Human Inheritance

Flashcards covering key vocabulary related to probability, pedigree analysis, and different modes of inheritance based on provided lecture notes.

Pedigrees

Charts that display inheritance patterns in humans.

Probability (Genetics)

Mathematical principles applied to predict inheritance patterns of traits.

Pedigree Symbols (Female)

Represented by a circle in a pedigree chart.

Pedigree Symbols (Male)

Represented by a square in a pedigree chart.

Pedigree Symbols (Express trait)

A filled-in shape indicating the individual has the trait.

Pedigree Symbols (Do not express trait)

An unfilled shape indicating the individual does not have the trait.

Pedigree Symbols (Deceased)

A shape with a line through it, often with a date of death.

Pedigree Symbols (Unspecified sex)

Represented by a diamond shape.

Pedigree Notation (Generations)

Roman numerals (I, II, III, etc.) indicating generations in a pedigree.

Pedigree Notation (Individuals)

Arabic numerals (1, 2, 3, etc.) indicating individuals within a specific generation in a pedigree.

Pedigree Lines (Parents)

A horizontal line connecting a male and female in a pedigree chart.

Pedigree Lines (Siblings)

Lines extending downwards from a parental line to offspring.

Pedigree Lines (Identical twins)

Represented by two lines branching from the same point on the parental line, connected by a horizontal line above the shapes.

Pedigree Lines (Fraternal twins)

Represented by two lines branching from the same point on the parental line, without a connecting horizontal line above the shapes.

Pedigree Lines (Adoption)

Represented by a dashed line connection to parents in a pedigree chart.

Pedigree Lines (Consanguineous Parents)

A double horizontal line connecting parents, indicating they are closely related by blood.

Sum Rule (Probability)

Used to calculate the probability of two or more mutually exclusive events: P(or) = P(event 1) + P(event 2).

Product Rule (Probability)

Used to calculate the probability of two or more independent events: P(and) = P(event 1) x P(event 2).

Autosomal Dominant Inheritance

A pattern where the trait is expressed if at least one dominant allele is present on an autosome; males and females are affected equally, and affected individuals typically have at least one affected parent.

Incomplete Penetrance (AD)

Occurs in autosomal dominant traits when an individual carries the gene but does not express the associated phenotype.

Autosomal Recessive Inheritance

A pattern where the trait is expressed only if two recessive alleles are present on an autosome; males and females are affected equally, and affected individuals can have unaffected carrier parents.

Calculating Risks in Pedigrees

A method involving identifying the mode of inheritance, known genotypes, carrier probabilities for unknown individuals, and multiplying probabilities using independent events.

Sex Determination in Mammals

Primarily determined by the presence or absence of the Y chromosome; the SRY gene on the Y chromosome initiates male development.

SRY gene

Sex-determining region Y gene, located on the Y chromosome, responsible for producing TDF.

TDF (Testis-Determining Factor)

A protein produced by the SRY gene that induces the medulla of the embryonic gonads to develop into testes.

Sex Linkage

The association of a characteristic with gender because the gene coding for it is located on a sex chromosome (typically the X chromosome).

Thomas Hunt Morgan's Conclusions

Experimental work demonstrating that genes are located on chromosomes and X-linked genes exhibit unique patterns of inheritance.

X-Linked Recessive Inheritance

A pattern where the recessive allele is on the X chromosome, predominantly affecting males; only the mother needs to be a carrier for a son to express the trait.

Hereditary Colorblindness

An X-linked recessive condition due to mutations in opsin 1 genes, primarily affecting red/green photoreceptors.

Hemophilia

An X-linked recessive bleeding disorder caused by a mutation in a clotting factor (Factor VIII) gene.

Duchenne Muscular Dystrophy

An X-linked recessive disorder characterized by a mutation in the dystrophin gene, leading to progressive muscle weakness.

X-Linked Dominant Inheritance

A pattern where the dominant allele is on the X chromosome; fathers transmit the trait to all daughters but never to sons, while mothers can transmit to both sons and daughters.

Rett Syndrome

An X-linked dominant neurodevelopmental disorder almost exclusively in females, often linked to MeCP2 mutations.

Fragile X Syndrome

An X-linked dominant disorder caused by a CGG repeat expansion in the FMR1 gene, associated with intellectual disability and autism.

Alport Syndrome

A kidney disease, which can be X-linked dominant, caused by mutations in collagen genes.