Genetic Inheritance Patterns Quiz

Genetic Inheritance Patterns

• Genetic inheritance patterns are studied using pedigrees, which are charts showing family history over generations.
• Pedigrees illustrate how traits are passed down (e.g., disease causes).
• They predict the likelihood of offspring inheriting a trait.
• Pedigrees reveal if a trait is dominant or recessive, and if the gene is autosomal or X-linked.

Pedigree Basics

• A pedigree is a chart depicting genetic history, spanning multiple generations.
• Pedigree illustrations contain symbols for males (squares), females (circles), affected individuals (filled shapes), heterozygotes (or carriers), matings, offspring order, twins, deceased individuals, spontaneous abortions, consanguineous marriages, and unknown sex.
• Pedigree analysis reveals the pattern of trait transmission.

Interpreting Pedigrees

• To determine dominance or recessiveness, observe if the disorder appears in every generation (dominant) or skips generations (recessive).
• Recessive traits might not manifest in parents but may appear in offspring.
• Consider heterozygosity when analyzing recessive traits, as parents may carry the trait without displaying it.

Evaluating Pedigree Charts

• Pedigree analysis involves checking if the trait appears in every generation (vertical transmission) or only one (horizontal).
• Note the ratio of affected males to females.
• Observe if the disease is passed through unaffected females or through male-to-male transmission.
• Examine what percentage of children are affected (e.g., all males, none).

Common Inheritance Patterns

• Autosomal Dominant: One affected parent often transmits the trait to offspring in each generation with similar proportions between males and females affected. Vertical pattern in pedigrees and affects both sexes.
• Autosomal Recessive: Traits appear sporadically. Two heterozygous carriers (both must carry the affected gene) have a higher chance of passing the trait to an offspring. Vertical pattern, affects males and females equally.
• X-linked Recessive: Traits are more likely to appear in males, passed from mother to son.

Vocabulary

• Character: A heritable feature.
• Trait: A variant of a character.
• Monohybrid cross: A cross tracking single character inheritance in a generation.
• P generation: Parental generation.
• F1 generation: First filial generation, offspring from the P generation.
• F2 generation: Second filial generation, offspring from the F1 cross.
• Punnett square: A tool to show possible offspring genotypes resulting from a cross.
• Allele: Alternate version of a gene.
• Dominant allele: Expressed in heterozygotes.
• Recessive allele: Not expressed in heterozygotes.
• Homozygote: Pair of identical alleles.
• Homozygous dominant: Pair of dominant alleles (e.g., BB).
• Homozygous recessive: Pair of recessive alleles (e.g., bb).
• Heterozygote: Pair of different alleles (e.g., Bb).
• Genotype: Genetic makeup.
• Phenotype: Expression of traits.

Autosomal Dominant Inheritance

• A trait's expression requires only one affected allele.
• Multiple generations are typically affected.
• Males and females are equally likely to be affected.
• Male-to-male transmission is possible.
• Affected individuals often have at least one affected parent (with exceptions in rare cases).

Complicating Factors

• Non-penetrance
• New mutation
• Adult-onset conditions
• Consanguinity
• Interaction
• Sex-limited/sex influenced
• Germline mosaicism
• Anticipation
• Heterogeneity
• Pleiotropy

Test your knowledge on genetic inheritance patterns using pedigrees. This quiz will cover pedigree basics, how to interpret them, and the distinction between dominant and recessive traits. Understand disease inheritance and the implications of genetic traits across generations.