Download Answers PDP Chapter 11.2

Name: ____________________________________
Title of Text: Ch. 11.2—Probability & Punnett Squares
PreDuringPost Cornell Notes
Essential Question(s):
How does biological information pass from one generation to another?
How can we use genetics to study human inheritance?
Prediction: I predict this section will be about using Punnett squares to understand probability in genetics.
Questions
1. What is the relationship between genetics
and probability?
Answers
Principles of probability can be used to predict
the outcomes of genetic crosses.
o A coin landing on heads or tails has
the same probability as a child being a
boy or girl (1/2)
2. What are Punnett squares? How are they
used in genetics?
Punnett squares can be used to predict and
compare the genetic variations that will result
from a cross.
o Homozygous have the same alleles for
a trait (i.e. TT) and are true-breeding.
o Heterozygous organisms have
different alleles for a trait (i.e. Tt) and
are hybrids.
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J.Adams/AEC/2010
PDP Cornell Notes
Questions
3. How are probability and segregation
related?
Answers
As seen in the Punnett square, the
probability for tall plants in the F2
generation was ¾ and ¼ for short. This 3:1
ratio of phenotypes was observed in
Mendel’s pea plants, therefore showing that
segregation of alleles did occur.
4. How do probabilities predict averages?
Probability does not predict the precise
outcome, but rather an average outcomes of
a large number of events.
The larger the number of offspring, the
closer the resulting numbers will be to the
expected results.
Vocabulary:
Probability: likelihood that particular event will
occur [probare—“to test or demonstrate”]
Punnett Square: diagram showing the gene
combination that might result from a genetic cross
Focus Words: Genetics, probability, Punnett
square, phenotype, genotype
Summary (20 word max): In genetics, Punnett
squares are used as a tool to predict the probability
of inheriting certain genotypes and phenotypes.
Homozygous: term used to refer to an organism
that has two identical alleles for a particular trait
[homo—“same”; zygon—“yoke”]
Heterozygous: term used to refer to an organism
that has two different alleles for the same trait
[heteros—“the other, another, different”]
Phenotype: physical characteristic of an organism
[phainein—“to show”]
Genotype: genetic makeup of an organism
[genos—“race, offspring”]
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J.Adams/AEC/2010