In guinea pigs, smooth coat (S) is dominant over rough coat...

In guinea pigs, smooth coat $(S)$ is dominant over rough coat $(s),$ and black coat $(B)$ is dominant over white coat $(b) .$ In the cross $S s B b \times S s B b,$ how many of the offspring will have a smooth black coat, on average? a. 1$/ 4$ b. about 9$/ 16$ C. 1$/ 16$ d. 6$/ 16$ e. 2$/ 6$

In guinea pigs, smooth coat $(S)$ is dominant over rough coat $(s),$ and black coat $(B)$ is dominant over white coat $(b) .$ In the cross $S s B b \times S s B b,$ how many of the offspring will have a smooth black coat, on average?
a. 1$/ 4$
b. about 9$/ 16$
C. 1$/ 16$
d. 6$/ 16$
e. 2$/ 6$

Key Concepts

Dominant and Recessive Alleles

This concept refers to how certain alleles can mask the expression of others. In genetics, a dominant allele will determine the phenotype even when a recessive allele is present, whereas the recessive trait will only appear if an individual has two copies of the recessive allele. It is fundamental for understanding how certain traits are inherited in organisms.

Independent Assortment

Mendel's principle of independent assortment states that alleles of different genes are distributed into gametes independently of one another, provided the genes are located on different chromosomes. This principle is crucial in predicting the probabilities of offspring inheriting combinations of traits when multiple genes are involved.

Dihybrid Cross

A dihybrid cross involves examining the inheritance of two different traits simultaneously, typically involving two pairs of contrasting alleles. It often leads to a characteristic phenotypic ratio that illustrates the combined probabilities of the independent traits, making it a key concept in understanding the inheritance patterns of multiple traits.

Punnett Square

A Punnett square is a graphical tool used to predict the outcome of a cross between two organisms. It helps organize and calculate the probability of inheriting specific traits by outlining all possible allele combinations from each parent, making it an essential method in performing dihybrid crosses and understanding Mendelian genetics.

Phenotypic Ratio

The phenotypic ratio is the proportion of offspring displaying a particular trait or combination of traits. It is derived from the underlying genotypic combinations predicted by techniques such as the Punnett square in crosses involving dominant and recessive alleles, and it provides a quantitative expectation for the appearance of traits among the offspring.

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