Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Mendel's Contribution: Gregor Johann Mendel, the 'Father of Genetics', used the garden pea () to study inheritance.
Alleles: Genes come in pairs called alleles. For example, the gene for height has alleles (tall) and (short).
Dominant vs. Recessive: A dominant allele (represented by capital letters like ) expresses itself even in the presence of a recessive allele (represented by ). Recessive traits only appear in homozygous conditions ().
Genotype and Phenotype: Genotype refers to the genetic makeup (e.g., , , or ), while Phenotype refers to the physical appearance (e.g., Tall or Short).
Law of Segregation: During gamete formation, the two alleles of a pair separate/segregate such that each gamete receives only one allele.
Law of Independent Assortment: When two pairs of traits are combined in a hybrid, the segregation of one pair of characters is independent of the other pair.
Monohybrid Cross: A cross involving a single pair of contrasting characters (e.g., height).
Dihybrid Cross: A cross involving two pairs of contrasting characters (e.g., seed shape and color).
📐Formulae
💡Examples
Problem 1:
A cross is made between a homozygous tall plant () and a homozygous short plant (). What will be the phenotype of the generation and the phenotypic ratio of the generation?
Solution:
In , all plants will be (Tall). In , the phenotypic ratio will be .
Explanation:
All offspring inherit one from the tall parent and one from the short parent. Since is dominant, they appear tall. In , the gametes and combine to form , , , and .
Problem 2:
In a dihybrid cross between Round-Yellow () and Wrinkled-Green () seeds, how many plants in the generation (out of 16) are expected to be Wrinkled-Yellow?
Solution:
out of plants.
Explanation:
According to the dihybrid phenotypic ratio , the distribution is: Round-Yellow, Round-Green, Wrinkled-Yellow, and Wrinkled-Green. Therefore, the frequency of the recombinant Wrinkled-Yellow phenotype is .
Problem 3:
If a purebred black dog () is mated with a purebred white dog (), what is the probability of getting a white dog in the generation?
Solution:
Explanation:
The generation will consist entirely of heterozygous black dogs () because the black allele () is dominant over the white allele (). Recessive traits () only reappear in the generation.