81. Genetics A Punnett square is a diagram that shows all possible gene combinations in a cross of parents whose genes are known. When two pink snapdragon flowers (RW) are crossed, there are four equally likely possible outcomes for the genetic makeup of the offspring: red (RR), pink (RW), pink (WR), and white (WW), as shown in the Punnett square at the left. When two pink snapdragons are crossed, what is the probability that the offspring will be (c) white?

Verified step by step guidance

1. Step 1: Understand the problem. The question asks for the probability that the offspring will be white (WW) when two pink snapdragon flowers (RW) are crossed. The Punnett square provided shows all possible genetic combinations.
2. Step 2: Analyze the Punnett square. The Punnett square shows four equally likely outcomes: RR, RW, WR, and WW. Each outcome represents a genetic combination of the offspring.
3. Step 3: Identify the desired outcome. The problem specifically asks for the probability of the offspring being white (WW). Locate the WW cell in the Punnett square.
4. Step 4: Count the occurrences of the desired outcome. In the Punnett square, there is one WW cell out of the four total cells.
5. Step 5: Calculate the probability. Since each outcome is equally likely, the probability of the offspring being white (WW) is the number of WW outcomes divided by the total number of outcomes, which is 1/4 or 25%.

Key Concepts

Punnett Square

A Punnett square is a graphical representation used in genetics to predict the possible genotypes of offspring from a cross between two parents. It organizes the alleles contributed by each parent, allowing for a visual assessment of the probability of various genetic combinations. In the case of pink snapdragons, the square illustrates the potential outcomes of crossing two RW (pink) flowers.

Genotype and Phenotype

Genotype refers to the genetic makeup of an organism, represented by the alleles inherited from its parents, while phenotype is the observable physical or biochemical characteristics resulting from the genotype. In the example of snapdragons, the genotypes RR, RW, WR, and WW correspond to the phenotypes red, pink, and white flowers, respectively. Understanding this distinction is crucial for interpreting genetic outcomes.

Probability in Genetics

Probability in genetics is used to determine the likelihood of specific traits being expressed in offspring based on parental genotypes. In the context of the Punnett square, the probability of obtaining a particular genotype or phenotype can be calculated by counting the occurrences of each outcome. For the pink snapdragons, the probability of producing a white flower (WW) can be derived from the total combinations shown in the square.