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Inheritance and Mendelian Genetics



a version of a gene

chromosomal crossing over

a process in which chromosomes swap portions of their arms, resulting in the redistribution of genetic material


a structure that contains DNA, the genetic material that is passed from one generation to the next


when two alleles are both expressed in the organism's phenotype

dominant allele

an allele whose expression masks that of another allele


when one gene "activates" another one

first filial generation (F1)

the first generation offspring resulting from a parental cross


a unit of heritable material that codes for a particular trait


the genetic makeup of an organism

Gregor Mendel

the scientist who discovered the principles underlying genes and inheritance


having two different alleles for a gene


having two identical alleles for a gene

incomplete dominance

when two alleles are blended in the organism's phenotype

law of independent assortment

the principle that states alleles of different genes are sorted into gametes independently of one another

linked genes

genes that are frequently inherited together (more than 50% of the time)


a process in cell division during which the number of chromosomes decreases to half the original number by two divisions of the nucleus, resulting in the production of gametes

Mendelian inheritance

patterns of inheritance that follow Mendel's laws of dominance and recessiveness, showing that some genes appear more often than others, and independent assortment, which suggests that genes are inherited randomly

non-Mendelian inheritance

patterns of inheritance that do not follow Mendelian patterns, such as codominance or polygenic inheritance

parent generation (P)

the original two organisms that are crossed to give offspring


an observable characteristic of an organism that results from genetic and environmental influences


when multiple phenotypes arise from a single gene

polygenic inheritance

when more than one gene codes for a single trait

Punnett square

a tool used to predict the possible genotypic outcomes of a cross between two individuals

recessive allele

an allele whose expression is masked by another allele

second filial generation (F2)

the offspring of a cross between individuals of the first generation

sex-linked trait

trait that is inherited on either the X or Y chromosome


a characteristic determined by an organism's genes