**Problem 4.3-4.** The gene for eye color in a certain male fruit fly has alleles (R, W). The gene for eye color in the mating female fruit fly also has alleles (R, W). Their offspring receive one allele for eye color from each parent. If an offspring ends up with either (R, R), (R, W), or (W, R), its eyes will look red. Let \( X \) equal the number of offspring having red eyes. Let \( Y \) equal the number of red-eyed offspring having (R, W) or (W, R) genes. (a) If the total number of offspring is \( n = 400 \), how is \( X \) distributed? (b) Give the values of \( E(X) \) and \( \text{Var}(X) \).
Percentage
A percentage is a number indicated as a fraction of 100. It is a dimensionless number often expressed using the symbol %.
Algebraic Expressions
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Numbers
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Subtraction
Before we begin to understand the subtraction of algebraic expressions, we need to list out a few things that form the basis of algebra.
Addition
Before we begin to understand the addition of algebraic expressions, we need to list out a few things that form the basis of algebra.
4.3-4
Introduction:
There are 4 possibilities of allele combinations: (R, R), (R, W), (W, R), and (W, W). These can be assumed to be equally likely, so that, the probability that a randomly selected offspring ends up with any one of these 4 combinations is 1/4 or 0.25.
Now, the eye of an offspring will be red if they end up with any one of (R, R), (R, W) or (W, R). In other words, the 3 out of the 4 possibilities will give rise to red eyes. Thus, the probability that an offspring has red eyes is 3/4 or 0.75.
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