11.3 Law of Independent Assortment

What are Pairs of Unit Factors (Genes)?

Mendel proposed the existence of paired unit factors (genes) responsible for heredity.

Explain Transmission of Genes

Mendel suggested that these unit factors are transmitted faithfully from generation to generation during gametogenesis and fertilization.

What are Discrete Units of Inheritance?

Mendel's experiments with pea plants and his observations of the F2 generation led him to deduce that hereditary factors are inherited as discrete units, not blended.

What is Independent Assortment?

Mendel's law of independent assortment states that genes do not influence each other's sorting of alleles into gametes, and every possible

How does Dihybrid Cross illustrate the Law of Independent Assortment?

The law of independent assortment can be illustrated through a dihybrid cross, where two true-breeding parents with different traits for two characteristics are crossed.

Explain Random Assortment of Alleles

The law of segregation requires that each gamete receives one allele from each gene, resulting in four equally likely gametes: RY, rY, Ry, and ry.

Explain the Physical Basis in Meiosis I for Law of Independent Assortment

The physical basis for the law of independent assortment lies in meiosis I, where homologous pairs align in random orientations, leading to the random assortment of alleles in gametes.

What are Complex Crosses?

When more than two genes are involved in a cross, the Punnett square method becomes cumbersome and impractical.

What is the preferred method for the Forked-Line Method?

The forked-line diagram is a preferred method for complex crosses involving multiple genes.

How do you Create a Forked-Line Diagram

To create a forked-line diagram, rows are made equal to the number of genes being considered, and alleles are segregated on forked lines based on probabilities for individual monohybrid crosses.

How do you Calculate Probabilities for the Forked-Line Method?

The values along each forked pathway are multiplied to obtain the probabilities of the F2 offspring genotypes, following the product rule.

What is the Probability Method for the Law of Independent Assortment?

The probability method provides proportions of offspring expected to exhibit each phenotype or genotype without the visual assistance of a diagram.

What is the Tetrahybrid Cross example for Probability Method?

In a tetrahybrid cross between heterozygotes for all four genes, and considering independent assortment in a dominant and recessive pattern, the proportion of offspring expected to be quadruply homozygous recessive is 1/256.

How do you Predict Genotypes and Phenotypes?

To predict genotypes and phenotypes in a multihybrid cross obeying independent assortment and a dominant and recessive pattern, determine the value of n, which represents the number of heterozygous gene pairs (genes segregating two alleles each).

What is Gene Linkage?

Gene linkage refers to genes located physically close to each other on the same chromosome, which are more likely to be inherited as a pair.

What is Recombination (Crossover)?

Recombination, or crossover, is the process during meiosis where segments of homologous chromosomes exchange genetic material, resulting in a shuffling of alleles.

What are Linked Genes?

When two genes are closely located on the same chromosome, they are considered linked, and their alleles tend to be transmitted together during meiosis.

What can the Proportion of Recombinant Gametes be used to calculate?

The proportion of recombinant gametes can be used to measure the distance between genes on a chromosome.

Genes located on separate non-homologous chromosomes always sort ____ during inheritance.

Genes located on separate non-homologous chromosomes always sort independently during inheritance.

Mendel’s Study on Epistasis discovered what?

Mendel's studies implied that single genes control individual characteristics (phenotypes), but in reality, most characteristics are influenced by multiple genes acting together.

In what ways may Genes Interact?

Genes may interact in various ways, such as complementary, synergistic, or antagonistic (epistasis).

Define Epistasis

In epistasis, one gene masks or interferes with the expression of another gene, resulting in one gene being hypostatic to the epistatic gene.

Example of Epistasis

An example of epistasis is pigmentation in mice, where a gene controlling pigment production (C) is epistatic to the gene controlling coat color (A).

Explain Masking of Expression for Epistasis

Epistasis can also occur when a dominant allele masks the expression of another gene, as seen in fruit color in summer squash.

What is Reciprocal Epistasis?

In reciprocal epistasis, either gene, when present in the dominant form, produces the same phenotype. An example is seed shape in the shepherd's purse plant (Capsella bursa-pastoris).

What does a Phenotypic Ratio of 16 of indicate?

Characteristics resulting in a phenotypic ratio totaling 16 often indicate a two-gene interaction, assuming the interacting genes are not linked.

What is linkage?

The phenomenon in which alleles that are located in close proximity to each other on the same chromosome are more likely to be inherited together

Define Law of Dominance

In a heterozygote, one trait will conceal the presence of another trait for the same characteristic

Define the Law of independent assortment

Genes do not influence each other with regard to sorting of alleles into gametes; every possible combination of alleles is equally likely to occur

General Rules for Multihybrid Crosses

Mice example for Epistasis