GENETICS MIDTERM REVIEWER

What initiated the study of genetic inheritance patterns beyond Mendelian ratios?

Mendel's work was rediscovered in the early 1900s.

What are alleles?

Alternative forms of the same gene.

What is a wild-type allele?

The allele that occurs most frequently in a population, often dominant and normal.

What is a mutant allele?

An allele that has modified genetic information, often producing an altered gene product.

What type of mutation results in reduced or eliminated function of the gene product?

Loss-of-function mutations.

What are gain-of-function mutations?

Mutations that enhance the function of the wild-type product.

What are neutral mutations?

Mutations that do not cause a detectable change in phenotype or functional impact.

What is a polygenic trait?

A trait influenced by multiple genes working together.

How are dominant alleles denoted in Mendelian genetics?

With an uppercase letter (e.g., D for tall).

How is a recessive allele denoted in Mendelian genetics?

With a lowercase, italicized letter (e.g., d for dwarf).

What is incomplete dominance?

When a cross between parents with contrasting traits produces offspring with an intermediate phenotype.

What genetic ratio results from a cross involving incomplete dominance?

1:2:1 genotypic ratio.

What is codominance?

When two alleles of a single gene produce two distinct, detectable gene products.

What is an example of codominance in humans?

The MN blood group.

What distinguishes multiple alleles for a gene?

There can be more than two alternative forms of the same gene present in a population.

What is a recessive lethal allele?

A mutation that leads to death in homozygous recessive individuals.

What is the Bombay phenotype?

Individuals expressing blood type O due to a recessive mutation at a separate locus affecting antigen synthesis.

What is epistasis?

When the expression of one gene masks or modifies the expression of another gene.

What is an example of sex-limited inheritance?

Feather plumage in domestic fowl.

What is sex-influenced inheritance?

A phenotype appears in both sexes but is expressed differently.

What is pleiotropy?

The phenomenon where a single gene influences multiple phenotypic traits.

What are temperature-sensitive mutations?

Mutations that are expressed under certain temperature conditions.

What is penetrance?

The percentage of individuals with a genotype who display the associated phenotype.

What is expressivity?

The degree or range of phenotypic expression for a given genotype.

What is the significance of maternal effect in genetics?

Offspring's phenotypes are determined by maternal nuclear genes acting before fertilization.

What is an organelle heredity?

Phenotypic traits influenced by genes in mitochondria or chloroplasts.

What is heteroplasmy?

A mix of normal and mutant organelles within a cell.

What does the crisscross pattern of inheritance refer to?

X-linked recessive traits passed from homozygous mothers to all sons.

What is meant by genetic anticipation?

A disorder's severity increases, and its onset occurs earlier in successive generations.

What role do mitochondria play in human health?

Mitochondrial dysfunction is linked to various diseases and aging.

What discovery did Edward B. Lewis contribute to genetics?

He played a pivotal role in establishing complement analysis within genetic research.

What is the main characteristic of dominant lethal alleles?

They cause death in individuals with just one copy of the allele.

What is the relationship between X-linked disorders and gender?

Many affect males primarily, as they express X-linked alleles without a second copy.

What impact do mutations in the Marfan syndrome gene have on human phenotypes?

They lead to lens dislocation, cardiovascular issues, and skeletal abnormalities.

What describes the expression of phenotypes in sex-influenced traits?

Expression that is different or more pronounced in one sex over another.

What does the term 'position effect' refer to?

The physical location of a gene affects its expression.

What is the outcome of complementation analysis?

Determines whether two mutations causing a similar phenotype are alleles of the same gene.

What is the importance of understanding penetrance and expressivity in genetics?

They help explain the variability in phenotypic expression.

What are examples of pleiotropic effects in human genetic disorders?

Marfan syndrome affecting multiple systems and Porphyria variegata causing various symptoms.

What is a characteristic of the polydactyl trait in humans?

It is an example of incomplete penetrance where not all individuals with the genotype display the phenotype.

What are two main types of extranuclear inheritance?

Organelle heredity and maternal effect.

What is the role of the Bicoid gene in Drosophila?

It regulates anterior embryonic development.