Chapter 7 a): Mendelian Genetics

Flashcards covering key concepts from the lecture on Mendelian genetics.

What does the theory of epigenesis state?

An organism is derived from substances present in the egg, which differentiate into adult structures during embryonic development.

What did Louis Pasteur contribute to biology?

He developed the germ theory, stating that all organisms are composed of cells derived from similar preexisting structures.

What does Mendel's Principle of Segregation say?

When any individual produces gametes, the alleles of a gene pair separate, ensuring each gamete receives only one member of the pair.

What is the phenotypic ratio observed in Mendel's F2 generation for a monohybrid cross?

Approximately 3:1 ratio, with dominant traits expressed more frequently.

Define homozygous.

A true breeding organism having two identical alleles for a given characteristic.

What is a Punnett square used for?

To predict the probability of possible genotypes of offspring from genetic crosses.

What is the significance of Mendel's test cross?

It determines the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive individual. This reveals whether the dominant phenotype is homozygous or heterozygous

What is incomplete dominance?

An inheritance type where one allele is not completely expressed over its paired allele, resulting in a blend of traits. (Ex: Red and white plant- pink offspring)

What does codominance refer to?

A situation where both parental traits appear together in the offspring's phenotype. (Ex: AB blood type, a mix of A and B alleles)

What is polygenic inheritance?

The additive effect of two or more gene loci on a single phenotypic characteristic. (Ex: human height or skin color)

Define epistasis.

Occurs when two or more different gene loci contribute to the same phenotype but not additively, with one gene masking or modifying the phenotype of another.

What are multiple alleles?

The occurrence of a gene that exists in three or more alleles in a population, as seen in the ABO blood group in humans.

What are alleles?

alternative forms of a gene; genes governing variation of the same character that occupy corresponding positions (loci) on homologous chromosomes.

What is a dihybrid cross?

A genetic cross in which the parents differ with respects to the alleles of two loci (EX: AAbb AaBa)

In the F2 generation of a dihybrid cross what are the results?

The results are a phenotypic ratio of 9:3:3:1 for the offspring, representing combinations of dominant and recessive traits from both loci. 2 phenotypes were similar to parents; the other 2 exhibit new combinations.

Explain Mendel’s Second Law - the law of independent assortment

States that alleles of different genes assort independently of one another during gamete formation, allowing for genetic variation.

What is pleiotropy?

The phenomenon where a single gene influences multiple phenotypic traits. This can lead to various effects on an organism's appearance or health. (Ex: sickle cell anemia affecting blood cells and physical health)