Mendelian Genetics Review

These flashcards cover key vocabulary and concepts associated with Mendelian genetics.

Gregor Mendel

• A scientist known as the father of genetics who performed experiments with pea plants and published findings in 1866.

• He proposed the rules of heredity without the knowledge of chromosomes, genes, or DNA

P generation

The parental generation in Mendel's experiments.

F1 generation

The first filial generation, which is the progeny resulting from parental mating.

Alleles

Alternate forms of a gene that can exist for a particular trait.

Genotype

The genetic constitution of an organism, representing the different alleles for a trait.

Phenotype

The observable traits or characteristics of an organism.

Monohybrid cross

A genetic cross that examines the inheritance of a single trait.

Dihybrid cross

A genetic cross that examines the inheritance of two traits simultaneously.

• follows Mendel’s second law of inheritance/law of independent assortment

Law of Segregation

The principle stating that the two alleles for a trait separate during gamete formation.

• monohybrids follow the law of segregation

Law of Independent Assortment

The principle stating that alleles for different traits segregate independently of one another during gamete formation.

Complete dominance

A situation where the phenotype of the heterozygote is identical to that of the dominant homozygote.

Incomplete dominance

A form of inheritance where the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes.

Codominance

A situation where both alleles in a heterozygote are fully expressed.

Punnett Square

A diagram used to predict the outcome of a genetic cross.

Epistasis

A genetic interaction where one gene affects the phenotypic expression of another gene.

Polygenic inheritance

An inheritance pattern where multiple genes influence a single trait.

This results in a continuous range of phenotypes, such as varying heights or skin color.

Sex-linked traits

Traits controlled by genes located on sex chromosomes, often leading to different expression in males and females.

Carriers

Individuals who carry one recessive allele for a trait and are phenotypically normal.

Lethal alleles

Alleles that lead to the death of an organism when present in a homozygous state.

Testcross

A breeding experiment used to determine the genotype of an organism by crossing it with a homozygous recessive.

Types of Crosses:

• Self cross = male + female gametes from same individual; self-fertilization

• inbreeding = brother-sister

• backcross = cross to one of the parents or parental types

• testcross = cross to homozygous recessive

Multiplicative Law of Simple Probability

The overall chance for the occurrence of 2 or more independent random events in exact order is equal to the product of their individual probabilities

Additive Law of Simple Probability

When there are multiple ways or tries for a chance outcome to occur, the overall probability is the sum of the individual events.

Dominantly Inherited Disorders

• dominant alleles that cause a lethal disease

• ex: Achondroplasia (form of dwarfism)

Recessively Inherited Disorders

• recessive allele

• can come from carriers that are heterozygous individuals

• Ex: albinism

Pleiotropy

• are responsible for the multiple symptoms of certain hereditary diseases such as cystic fibrosis and sickle-cell disease

• a gene that has multiple PHENOTYPIC effects

• Pleiotropic genes that affect multiple traits

Recombination

the process of crossover occurs when 2 homologous chromosomes align during meiosis and exchange a segment of genetic material