Genetics Lecture Review: Inheritance Patterns and Pedigree Analysis

Flashcards covering key vocabulary, concepts, and inheritance patterns from the lecture notes on single-gene inheritance, sex linkage, and human pedigree analysis.

Sex chromosomes

Special chromosomes (e.g., X and Y) that determine the sex of an individual.

Autosomes

Non-sex chromosomes, typically represented as 'A'.

Differential region

Regions on sex chromosomes (like X and Y) that have different DNA sequences, accounting for sex linkage.

Pseudoautosomal region

Regions of sequence similarity on X and Y chromosomes that allow them to pair during meiosis in male cells, where genes behave like autosomal genes.

Sex-linked genes

Genes located on the differential region of the sex chromosomes (usually X chromosome), producing different phenotypic ratios in males and females.

Homogametic sex

The sex that has two identical sex chromosomes (e.g., XX in humans and Drosophila), typically female.

Heterogametic sex

The sex that has two different sex chromosomes (e.g., XY in humans and Drosophila), typically male.

Nettie Stevens

The scientist who discovered sex chromosomes in Tenebrio (flour beetle) in 1905.

Thomas Morgan

The scientist who discovered red-eyed and white-eyed Drosophila in 1910, linking eye color to sex chromosomes.

Wild type (w+)

The common, naturally occurring phenotype, often red eyes in Drosophila.

Mutant (w)

A variation from the wild type, often white eyes in Drosophila.

Reciprocal crosses

Crosses where the phenotypes of the male and female parents are swapped, used to diagnose sex linkage if they yield different F1 results.

X chromosome inactivation

The process in somatic cells of female mammals where one of the two X chromosomes is randomly inactivated to achieve dosage compensation.

Dosage compensation

A mechanism to equalize the expression of genes on the X chromosome between males and females.

Calico cats

Female cats heterozygous for a sex-linked coat color gene that exhibit a mosaic phenotype due to X chromosome inactivation.

Pedigree analysis

The application of Mendelian principles to elucidate inheritance patterns in human families using family diagrams.

Pedigree

A family diagram that visually represents the inheritance of a trait or disease across multiple generations using standardized symbols.

Propositus (or Proband)

The individual in a pedigree who first brings the trait or condition to the attention of a geneticist or physician.

Autosomal dominant pedigree characteristics

A trait appears in every generation, affected parents can have unaffected children, and there is no correlation between sex and phenotype.

Autosomal recessive pedigree characteristics

Unaffected individuals can have affected offspring, and there is no correlation between sex and phenotype.

Expressivity

The degree to which a particular genotype is expressed phenotypically, which can vary among individuals with the same genotype.

Penetrance

The proportion of individuals with a particular genotype (or disease-causing allele) who actually show the expected phenotype.

Huntington disease

An example of a dominant autosomal human trait characterized by late onset, caused by CAG repeats in the Huntingtin protein gene.

X-linked recessive disorder characteristics

The phenotype is more common in males, affected fathers do not have affected children, and the trait is often passed from a grandfather through a carrier daughter to a grandson.

Hemophilia

An example of an X-linked recessive disorder, known for its inheritance pattern observed in European royalty.

X-linked dominant disorder characteristics

Fathers pass the trait to all of their daughters but to none of their sons; mothers pass the trait to approximately half of their sons and daughters.