Unit 2 Genetics

What plant did Mendel use for his genetic experiments?

Pisum sativum, the garden pea plant.

What is a key characteristic of Pisum sativum in nature?

It is self-fertilizing.

What does self-fertilizing mean for the traits of Pisum sativum?

Traits remain pure in the wild.

Can Pisum sativum be cross-fertilized experimentally?

Yes, it can be easily cross-fertilized experimentally.

How many distinguishable characters did Mendel choose for his experiments?

Seven distinguishable characters.

What are the traits of the characters Mendel studied?

Each character had only two contrasting traits.

Give an example of a character Mendel studied and its contrasting traits.

Seed color: yellow and green.

What is a monohybrid cross?

The experimental mating of two individuals with contrasting forms of a character.

What does P1 represent in Mendelian genetics?

The parental generation.

What does F1 represent in Mendelian genetics?

The first filial generation (offspring from P1).

What does F2 represent in Mendelian genetics?

The second filial generation (offspring from F1).

What is the Mendelian monohybrid genotypic ratio?

1:2:1.

What is the Mendelian monohybrid phenotypic ratio?

3:1.

What determines each trait in Mendel's experiments?

A unit factor.

What are the dominant and recessive alleles for seed shape?

R: round (dominant), r: wrinkled (recessive).

What are Mendel's first three postulates?

1. Unit factors in pairs. 2. Dominance/Recessiveness. 3. Segregation.

What does Mendel's law of segregation refer to?

The separation of paired unit factors during gamete formation.

What is a testcross?

A cross of an individual showing a dominant trait with a homozygous recessive individual.

What phenotypic ratio would you expect from a testcross?

1:1.

What is a dihybrid cross?

A cross that studies two independent characters simultaneously.

What is the Mendelian dihybrid phenotypic ratio?

9:3:3:1.

What is Mendel's fourth postulate?

Independent assortment.

What does independent assortment mean in genetics?

Segregating pairs of unit factors assort independently during gamete formation.

What is the product rule in genetics?

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

How many different types of gametes can an individual with genotype RrYy produce?

Four different types: Ry, rY, ry, and RY.

What does the term 'locus' refer to in genetics?

An exact location on a chromosome.

What is the significance of homologous chromosomes in Mendelian genetics?

Genes occur in pairs on homologous chromosomes.

What is the relationship between Mendel's laws and meiosis?

Mendel's laws of segregation and independent assortment correspond to events in meiosis.

What is the expected outcome of a cross between a black and a white guinea pig in Mendelian genetics?

F1 generation will be all black; F2 generation will be 3/4 black and 1/4 white.

What is the purpose of a Punnett square in genetics?

To diagram and predict the outcomes of genetic crosses.

What is the purpose of a testcross?

To determine the genotype of an individual exhibiting a dominant phenotype by crossing it with a homozygous recessive individual.

What is the phenotypic ratio for a Mendelian monohybrid cross?

3:1 for dominant to recessive traits.

What does Mendel's law of segregation state?

During gamete formation, paired unit factors separate randomly so that each gamete receives one factor with equal likelihood.

What is the significance of the Punnett square?

It is a diagram used to predict the genotypes and phenotypes of offspring from a genetic cross.

What is independent assortment?

The principle that alleles for different traits segregate independently of one another during gamete formation.

What is the genotype of a homozygous individual?

An individual with two identical alleles for a gene.

What is the genotype of a heterozygous individual?

An individual with two different alleles for a gene.

What are unit factors in Mendelian genetics?

The genetic determinants (alleles) that exist in pairs in an individual.

What does the term 'allele' refer to?

Alternative variants of a gene that result in contrasting traits for a character.

What is the role of meiosis in Mendelian genetics?

Meiosis is the process that leads to the formation of gametes and the segregation of alleles.

What is the expected outcome of a testcross involving a heterozygous individual?

The phenotypic ratio would be 1:1.

What does the term 'phenotype' mean?

The physical expression of a trait resulting from an individual's genotype.

What is the significance of the branch diagram in genetics?

It is used to determine phenotypic ratios from a dihybrid cross without working with gametes.

What is a character in Mendelian genetics?

A heritable feature that varies among individuals, such as seed color or flower position.

What is the expected result of a monohybrid cross between two heterozygous parents?

The genotypic ratio is 1:2:1.

What are the seven characters studied by Mendel in garden pea plants?

Seed color, seed shape, seed coat, pod color, pod shape, flower position, stem length.

What does the term 'homozygote' refer to?

An individual with two copies of the same variant (allele) of a gene.

What is the role of dominant and recessive alleles?

Dominant alleles mask the effect of recessive alleles in the phenotype.

What is the expected outcome of a dihybrid cross between two heterozygous parents?

The phenotypic ratio is 9:3:3:1.

What does the term 'locus' refer to?

The specific location of a gene on a chromosome.

What is the result of segregation during anaphase I of meiosis?

The separation of homologous chromosomes, leading to the formation of gametes with different alleles.

What is the expected phenotypic ratio for a testcross involving two characters?

1:1:1:1.