Genetic Crosses and Pedigrees 2025

Mendelian Inheritance

A type of biological inheritance that follows the laws proposed by Gregor Mendel in 1865.

Punnett Square

A diagram used to predict the outcome of a particular genetic cross or breeding experiment.

Monohybrid Cross

A cross between individuals differing in one trait.

Dihybrid Cross

A cross between individuals differing in two traits.

Autosomal Dominant

Only one copy of the dominant gene is needed for the characteristic to be present.

Autosomal Recessive

Both copies of the gene must be present for the characteristic to be exhibited.

X-Linked Dominant

The dominant gene is located on the X chromosome; only one copy needed for the characteristic to be present.

X-Linked Recessive

Both copies of the recessive gene are required in females, but only one in males for the characteristic to be present.

Test Cross

A breeding of a genetically unknown individual with a phenotypically recessive individual to determine the genotype.

Fill in the Blank - A test cross involves breeding a genetically unknown individual with a __ individual.

Phenotypically recessive.

Expected Genotypic Ratio from Dihybrid Cross

9:3:3:1.

Independent Assortment

The principle that genes on different chromosomes assort independently of each other.

Linked Genes

Genes that are found on the same chromosome and are more likely to be inherited together.

Pedigree Chart

A family tree that shows the occurrence and appearance of phenotypes of a particular gene and its inheritance.

Sex-Linked Traits

Traits associated with genes located on the sex chromosomes, primarily the X chromosome.

Allele

Different versions of a gene that may produce distinguishable phenotype effects.

Heterozygous

An organism that has two different alleles for a particular gene.

Homozygous

An organism that has two identical alleles for a particular gene.

Recombination Frequency

The frequency with which a single chromosomal crossover will take place between two genes during meiosis.