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6th Grade Science / Lesson 5 - Offspring

What will we be learning today?

  • In this lesson, we are going to learn all about what determines how offspring look.

What Determines How Offspring Look?

  • You know how to predict the probable outcome of tossing a single coin. What if you tossed two coins at once? Each coin has two sides, so there are four possible outcomes. Each outcome has a 25% chance of being the result of a single toss. If coin 1 and coin 2 are tossed at the same time, there is one chance in four that both coins will land heads up. The probability that both coins will land tails up is also one chance in four, or 25%.

Notice that there are two ways in which the toss could result in a combination of heads and tails-coin 1 heads and coin 2 tails, or coin 1 tails and coin 2 heads. The probability of each heads-tails outcome is one chance in four, or 25%. Since there are two heads-tails combinations, the probability of getting heads-tails is 50%. The ratio of all four possible outcomes is 25% heads-heads, 50% heads-tails, and 25% tails-tails, or 1:2:1

   Tossing two coins at once can result in four possible    outcomes.

  • The possible outcomes of a two-coin toss are very similar to those of a genetic cross. Geneticists use the laws of probability to predict the results of genetic crosses. Why?

  • There are two possible factors for a trait. Each parent, like a coin, has two factors for a trait. Like tossing two coins, two parents give a factor each for a trait to the offspring. The offspring, like the result of a two-coin toss, gets two factors, one from each parent.

Let's Review What We Learned Today!

  • Now complete your worksheet!

Try tossing two coins at the same time. Mark one coin "1" on both sides. Mark the other "2" on both sides. Record your results of 1 to 100 tosses.