chapter 20 Genetic Inheritance Practice Flashcards

Comprehensive vocabulary flashcards covering basic genetic principles, inheritance patterns, genetic disorders, and complex inheritance from Chapter 21.

Genotype

The genes of an individual, which code for specific traits.

Locus

The specific position on a chromosome where a gene is located.

Allele

An alternate form of a gene, such as an allele for blue eyes versus one for brown eyes.

Dominant Allele

An allele that masks the expression of a recessive allele; only one copy must be present for the trait to be expressed.

Recessive Allele

An allele that requires both chromosomes to possess it in order for the trait to be expressed.

Homozygous Dominant

A genotype where both alleles are dominant ($AA$).

Homozygous Recessive

A genotype where both alleles are recessive ($aa$).

Heterozygous

A genotype containing one dominant and one recessive allele ($Aa$).

Phenotype

The physical appearance of a trait, which is directed by the genotype.

Monohybrid Cross

A one-trait cross that examines the inheritance patterns of a single set of alleles for a single characteristic.

Two-Trait Cross

A genetic cross that explores the inheritance patterns for two different characteristics simultaneously.

Punnett Square

A tool used to predict the outcome of a cross by lining up all possible alleles for sperm on one side and eggs on the other.

Genotypic Ratio (Monohybrid)

The ratio of genotypes in a cross of two heterozygotes, typically predicted as $1:2:1$ ($1\text{ }FF:2\text{ }Ff:1\text{ }ff$).

Phenotypic Ratio (Monohybrid)

The ratio of physical appearances in a cross of two heterozygotes, typically predicted as $3:1$, where three individuals show the dominant trait.

Product Rule

The law of probability stating that the chance of two different events occurring simultaneously is equal to the multiplied probabilities of each event occurring separately.

Sum Rule

The law of probability where individual probabilities are added to determine the total probability for an event (applied to "or" cases).

Dihybrid Cross Phenotypic Ratio

The expected phenotypic ratio for a dihybrid cross with simple dominance, which is always $9:3:3:1$.

Autosomal Dominant Genetic Disorder

A disorder where individuals with genotypes $AA$ or $Aa$ will have the condition, and affected children usually have at least one affected parent.

Autosomal Recessive Genetic Disorder

A disorder where only individuals with the genotype $aa$ have the condition, often appearing in children of unaffected parents.

Pedigree

A chart showing the pattern of inheritance for a trait within a family, where males are squares and females are circles.

Carrier

A heterozygote who carries a recessive allele but exhibits the dominant phenotype.

Tay-Sachs Disease

An autosomal recessive disorder caused by a lack of the hex A lysosome enzyme, leading to fatty acid protein buildup in the brain and death by age $5$.

Cystic Fibrosis (CF)

An autosomal recessive disorder caused by a defective chloride channel encoded by the CFTR allele on chromosome $7$, resulting in thick mucus in bronchial tubes.

Sickle-cell Disease

An autosomal recessive disorder prevalent among African Americans where abnormal hemoglobin causes red blood cells to be sickle-shaped and live only $2$ weeks.

Marfan Syndrome

An autosomal dominant disorder and example of pleiotropy caused by a defect in fibrillin, resulting in long limbs, caved-in chest, and weakened aorta.

Osteogenesis Imperfecta

An autosomal dominant disorder characterized by weakened, brittle bones due to mutations in genes for type I collagen.

Huntington’s Disease

An autosomal dominant disorder causing progressive brain cell degeneration via clumps of the protein huntingtin, usually appearing in the late $30s$ to late $40s$.

Polygenic Traits

Traits controlled by several sets of alleles, such as skin color and height, which result in a bell-shaped curve distribution.

Multifactorial Traits

Traits controlled by polygenes that are subject to environmental influences, such as allergies, cancers, and diabetes.

Pleiotropy

A phenomenon where a single mutant gene affects two or more distinct and seemingly unrelated traits.

Incomplete Dominance

A pattern where the heterozygote has an intermediate phenotype, such as in Familial hypercholesterolemia where $Aa$ individuals have half the normal number of LDL receptors.

Codominance

A pattern of inheritance where alleles are equally expressed in a heterozygote, such as in type AB blood.

Autosomes

The $22$ pairs of chromosomes that are the same in both males and females and do not determine sex.

Sex-Linked Traits

Traits controlled by genes on the sex chromosomes; most are X-linked because the X chromosome is larger and carries more genes.

Duchenne Muscular Dystrophy

An X-linked recessive disorder caused by the absence of the protein dystrophin, leading to muscle degeneration and death usually by ages $20\text{ to }25$.

Fragile X Syndrome

An X-linked recessive disorder that is the most common cause of inherited intellectual disability and the most common known cause of autism spectral disorder.

Hemophilia

An X-linked recessive disorder where blood does not clot well; Type A is the absence of clotting factor VIII and Type B is the absence of factor IX.