Mendelian Genetics, Probability, and Chi-Squared Analysis

Vocabulary flashcards covering Mendelian inheritance, monohybrid and dihybrid crosses, probability principles, and chi-squared test analysis.

Genetics

The study of inheritance in biology.

Gregor Mendel

An Austrian monk born July 20, 1822, who studied mathematics and physics, conducted hybridization experiments in monastery gardens between 1856 and 1863, and published his foundational principles of inheritance in 1865.

Pisium Sativum

The scientific name of the garden pea plant used by Gregor Mendel in his inheritance experiments from 1856 to 1863.

Gene

The fundamental unit of inheritance located at a specific locus on a chromosome within the cell nucleus that carries information for a particular characteristic.

Allele

An alternate form of the same gene; every gene in an organism carries a pair of alleles.

Homozygous

The condition of having identical alleles for a particular gene.

Heterozygous

The condition of having two different alleles for a particular gene.

Dominant Allele

An allele that suppresses the physical expression of an alternative allele when both are present together.

Recessive Allele

An allele whose phenotypic expression is suppressed by a dominant allele and is only visible when an individual is homozygous for that allele.

Monohybrid Inheritance

A pattern of inheritance involving the transmission and expression of a single gene controlling a single characteristic.

Law of Segregation

Mendel's First Law, stating that each characteristic is controlled by a pair of factors (alleles) that separate during meiosis, resulting in only one factor entering each gamete.

First Filial Generation ($F_1$)

The initial generation of offspring produced from the mating of the parental generation.

Second Filial Generation ($F_2$)

The generation of offspring obtained by self-fertilization or interbreeding of individuals from the $F_1$ generation.

Test Cross

A breeding technique where an organism displaying a dominant phenotype of unknown genotype is crossed with a homozygous recessive individual to determine whether it is homozygous or heterozygous.

Dihybrid Cross

A genetic cross between individuals in which the inheritance of two distinct pairs of alleles or traits is examined simultaneously.

Law of Independent Assortment

Mendel's Second Law, which states that each pair of factors (alleles) segregates independently of any other pair during gamete formation.

Dihybrid Phenotypic Ratio

The characteristic $9:3:3:1$ ratio observed among the four phenotypic classes in the $F_2$ generation of a dihybrid cross involving two heterozygous parents.

Probability

The likelihood of an event occurring, mathematically expressed as $\frac{x}{N}$, where $x$ is the number of ways a particular event can occur and $N$ is the total number of possible outcomes.

Product Rule

A probability rule stating that the joint probability of two independent genetic events occurring together is equal to the product of their individual probabilities.

Chi-Squared ($\chi^2$) Test

A statistical test used to evaluate the validity of experimental data by assessing whether the difference between observed frequencies ($O$) and expected frequencies ($E$) is statistically significant.

Chi-Squared Statistic Formula

The formula used to calculate the test statistic: $\chi^2 = \sum \frac{(O - E)^2}{E}$, where $O$ represents observed frequencies and $E$ represents expected frequencies.

Null Hypothesis

The statistical proposition stating that there is no significant difference between observed experimental values and expected values.

Degrees of Freedom ($df$)

A statistical parameter calculated as $df = n - 1$, where $n$ equals the number of distinct phenotypic categories being evaluated in a chi-squared test.

Critical Value

The threshold value derived from a chi-squared distribution table at a specified degrees of freedom and confidence level, used to decide whether to accept or reject the null hypothesis.