Mendelian Inheritance

Question 1

Early thinking…

Answer 1

Blended Inheritance, offspring is a combination of the two parents

Question 2

Gregor Mendel

Answer 2

Came up with the principles of segregation and independent assortment. Experimented on pea plants. Would cross different plants to determine the outcome, by hand-pollinating specific plants with a paintbrush and would cover them with a net so there was no contamination.

Question 3

Crossing True-Breeding Strains

Answer 3

Trait that appears in the F1 generation is dominant, trait that does not is recessive.

Question 4

Crossing F1 Strains

Answer 4

3:1 ratio of phenotypic traits. Genotypic ratio would be 1:2:1.

Question 5

Testcross

Answer 5

Involves breeding an individual of an unknown genotype with a true breeding recessive and can determine the unknown genotype.

Question 6

Incomplete Dominance

Answer 6

The phenotype of the heterozygote is intermediate between the two homozygous genotypes. Superscripts are used instead of uppercase and lowercase because neither allele dominates the other.

Question 7

Independant Assortment

Answer 7

The inheritance of one gene pair does not affect the inheritance of another gene pair. This statement does not always hold, but does for genes on two different chromosomes.

Reflects the fact that in meiosis chromosomes can orient in different ways, how they line up on the metaphase plate, and nonhomologous chromosomes line up independantly of one another.

Question 8

Crossing Two traits

Answer 8

List possible gamete combinations on each side, one side is the maternal the other is the paternal. Crossing heterozygotes of both traits leads to a 9:3:3:1 ratio in phenotype.

Question 9

Principle of Segregation

Answer 9

Individuals inherit two copies of each gene, one from the mother and one from the father, and these two copies separate equally in the eggs and sperm.

Question 10

Epistasis

Answer 10

Expression of one allele is affected by another. Two alleles can be on the same chromosome or not.

Question 11

Incomplete Penetrance

Answer 11

Individuals with a genotype corresponding to a trait do not actually show the phenotype either because of environmental effects or because of interactions with other genes. Ex. being predisposed to cancer

Question 12

Variable Expressivity

Answer 12

Phenotype is expressed but with a different degree of severity in different individuals. ex. Marfan