Mendel and Heredity Lecture Review

Comprehensive practice flashcards covering Gregor Mendel's experiments, laws of inheritance, genetic terminology, and Punnett square probability ratios.

According to Mendel's research, how are traits inherited?

Traits are inherited as discrete units, which are now known as genes.

What is the definition of genetics?

The study of biological inheritance patterns and variation in organisms.

What were the three key decisions Mendel made in his experiments with pea plants?

The use of purebred plants, control over breeding, and the observation of seven "either-or" traits.

How did Mendel control the fertilization of his pea plants?

He interrupted the self-pollination process by removing the male flower parts, or stamens, and fertilizing the female part, the pistil, with pollen from a different pea plant.

In Mendel's cross between purebred white and purple plants, what were the results for the $F_1$ and $F_2$ generations?

In the $F_1$ generation, all plants had purple flowers; in the $F_2$ generation, white flowers reappeared in some offspring.

What is a purebred line of plants?

A line of plants that has self-pollinated for a long period of time to become genetically uniform.

What are the three conclusions that make up the Law of Segregation (Mendel's first law)?

1. Traits are inherited as discrete units; 2. Organisms inherit two copies of each gene, one from each parent; 3. The two copies separate during gamete formation.

What is the definition of a gene?

A piece of DNA that provides instructions to a cell to make a certain protein and has a specific location on a chromosome.

What is an allele?

Any alternative form of a gene occurring at a specific locus on a chromosome.

What is the difference between homozygous and heterozygous alleles?

Homozygous describes two alleles that are the same at a specific locus, while heterozygous describes two alleles that are different.

Define dominant and recessive alleles.

A dominant allele is expressed when at least one copy is present (represented by uppercase letters), while a recessive allele is expressed only when two copies are present (represented by lowercase letters).

Compare genotype and phenotype.

Genotype refers to the genetic makeup of a specific set of genes, while phenotype is the physical expression of a trait or the physical characteristics of an individual.

What is the genome?

All of an organism’s genetic material.

What is a Punnett square?

A grid system for predicting all possible genotypes resulting from a cross, where axes represent possible gametes of each parent and boxes show possible genotypes of offspring.

What is a monohybrid cross?

A cross that examines the inheritance of only one specific trait.

What is the genotypic ratio resulting from a cross between two heterozygous parents? ($Aa \times Aa$)

A ratio of $1:2:1$ ($\text{Homozygous Dominant: Heterozygous: Homozygous Recessive}$).

What is the ratio resulting from the cross of heterozygous and homozygous recessive parents?

A ratio of $1:1$ ($\text{Heterozygous: Homozygous Recessive}$).

What is a testcross?

A cross between an organism with an unknown genotype and an organism with the recessive phenotype.

What is a dihybrid cross and what phenotypic ratio did Mendel observe in heterozygous dihybrid crosses?

A dihybrid cross involves two traits; Mendel observed a phenotypic ratio of $9:3:3:1$. Boris

What is Mendel's second law and what does it state?

The law of independent assortment; it states that allele pairs separate independently of each other during meiosis.

What is the formula for probability as provided in the notes?

$$\text{Probability} = \frac{\text{number of ways a specific event can occur}}{\text{number of total possible outcomes}}$$