Chapter 3 Mendelian Genetics

What significant contribution did Gregor Mendel make in 1866?

He published his research on garden peas, demonstrating that units of inheritance exist.

What is the field established by correlating chromosome behavior during meiosis with Mendel's principles?

Transmission genetics, which studies how genes are transmitted from parents to offspring.

Why did Mendel choose garden peas for his experiments?

They are easy to grow and hybridize, have true-breeding strains, allow controlled matings, and mature in one season.

What are the seven visible features Mendel followed in his experiments?

Each feature had two contrasting forms (traits).

What is a monohybrid cross?

A cross involving only one pair of contrasting traits to reveal how one trait is transmitted from generation to generation.

What were the results of Mendel's monohybrid cross between tall and dwarf plants?

The F1 generation was all tall plants, while the F2 generation showed a 3:1 ratio of tall to dwarf plants.

What is the definition of genotype?

The genetic (allelic) makeup of an individual for a specific trait.

What is the definition of phenotype?

The physical expression of a trait resulting from the genotype.

What does Mendel's first postulate state about unit factors?

Genetic characters are controlled by unit factors existing in pairs in individual organisms.

What does Mendel's second postulate of dominance/recessiveness state?

One unit factor is dominant over another when two unlike unit factors are present for a single character.

What is Mendel's third postulate regarding segregation?

Paired unit factors segregate randomly during gamete formation, so each gamete receives one or the other with equal likelihood.

What is a testcross used for?

To determine if an individual displaying a dominant phenotype is homozygous or heterozygous for that trait.

What is a dihybrid cross?

A cross involving two pairs of contrasting traits, generating a unique F2 ratio.

What is the F2 generation ratio resulting from Mendel's dihybrid cross?

A 9:3:3:1 ratio.

What does Mendel's fourth postulate of independent assortment state?

During gamete formation, segregating pairs of unit factors assort independently of each other.

What is the product law of probabilities?

The combined probability of two independent events is equal to the product of their individual probabilities.

How can the fork-line method be used in genetics?

It simplifies the analysis of inheritance for larger numbers of traits by applying the product law of probability.

What is a trihybrid cross?

A cross involving three pairs of contrasting traits, following the same principles of segregation and independent assortment.

What are true-breeding traits?

Traits that appear unchanged generation after generation in self-fertilizing plants.

What is the significance of the F1 and F2 generations in Mendel's experiments?

F1 generation results from the initial cross, while F2 results from self-fertilization of F1 individuals.

What is the role of alleles in genetics?

Alleles are alternative versions of genes that determine traits.

What is the difference between homozygous and heterozygous genotypes?

Homozygous genotypes have identical alleles (e.g., DD, dd), while heterozygous genotypes have different alleles (e.g., Dd).

What does the term 'reciprocal cross' refer to?

A cross where the F1 and F2 patterns are similar regardless of the source of pollen and ovum.

How does Mendel's work relate to modern genetics?

His principles laid the foundation for understanding inheritance patterns and the behavior of genes.

What is the significance of the Punnett square in genetics?

It visualizes the genotypes and phenotypes resulting from a genetic cross.

What is the importance of controlled matings in Mendel's experiments?

They allowed Mendel to study inheritance patterns without external variables affecting the outcomes.

What is the relationship between genotype and phenotype?

The genotype determines the phenotype, which is the observable expression of a trait.