Chapter 4 – Extensions to Mendelian Genetics (VOCAB Flashcards)

Vocabulary flashcards covering key terms from Extensions to Mendelian Genetics, including wild-type vs mutant, penetrance and expressivity, dominance patterns, sex-linked traits, lethal alleles, and gene interactions.

Wild-Type Allele

An allele that is prevalent in natural populations and encodes a protein that functions normally and is produced in proper amounts.

Genetic Polymorphism

Presence of more than one wild-type allele in a population.

Mutant Allele

An allele that arises from mutation and often produces defective or altered proteins.

Loss-of-Function Allele

A common mutant allele that reduces or abolishes the function of the encoded protein and is usually recessive.

Gain-of-Function

A dominant mutant effect where the mutant protein gains a new or abnormal function.

Dominant-Negative

A mutant protein that interferes with the normal protein's function, reducing wild-type activity.

Haploinsufficiency

A condition in which one copy of a gene is not sufficient to produce the wild-type phenotype.

Incomplete Penetrance

A dominant allele that does not always produce the expected phenotype.

Expressivity

The degree to which a trait is expressed in an individual.

Penetrance

The proportion of individuals with a genotype who display the phenotype.

Incomplete Dominance

A heterozygote exhibits an intermediate phenotype between the two homozygotes.

Codominance

A heterozygote expresses the phenotypes of both alleles equally.

Multiple Alleles

Genes that have more than two alleles in a population (e.g., ABO blood groups).

Sex-Linked Genes

Genes located on sex chromosomes; X-linked and Y-linked inheritance.

X-linked

Genes on the X chromosome; males are hemizygous and more affected by recessive alleles.

Y-linked (Holandric)

Genes on the Y chromosome; few in number and transmitted father-to-son.

Sex-Influenced Traits

Autosomal traits where the phenotype's dominance differs between sexes.

Sex-Limited Traits

Traits expressed in only one sex due to sex-specific hormonal regulation.

Heterozygote

An individual with two different alleles at a locus.

Lethal Alleles

Mutant alleles that cause death due to mutations in essential genes; often recessive.

Conditional Lethal

Lethality that depends on environmental conditions.

Semilethal

Lethality affects only a portion of individuals carrying the allele.

Manx Cats (Manx Mutation)

Dominant mutation for short tails that is lethal in homozygous form.

Huntington’s Disease

A dominant lethal allele with late onset.

Dominant Lethal

A lethal allele that causes death when present in the heterozygous or homozygous state depending on the case.

Epistasis

One gene masks the phenotypic effect of another.

Complementation

Crossing individuals with the same recessive phenotype yields wild-type offspring, indicating mutations in different genes.

Pleiotropy

A single gene affects multiple phenotypic traits.

Gene Redundancy

One gene compensates for the loss of another, often due to paralogous gene duplicates.

Paralogs

Duplicated genes in the genome that can compensate for each other.

Gene Knockouts

Experimentally disabling a gene to study its function and effects.

Hemizygous

Males have only one X-linked allele; only one allele is present at X-linked loci.

Pseudoautosomal Inheritance

Genes on the sex chromosomes that are inherited like autosomal genes due to homologous regions and recombination.

9:7 Epistasis Ratio

A modified Mendelian ratio observed in some epistatic interactions, often 9:7 in the F2 generation.