Chapter 10: Patterns of Inheritance
-Connect the concepts of probability and randomness to the study of heredity (genetics).
-Contrast the blending hypothesis with the particulate hypothesis of inheritance.
-Explore explanations of inheritance that are not supported by experimental results.
-Describe some of the monk Mendel’s procedures for his plant-breeding experiments 10.1.
–Explain Mendel’s principle of segregation.
-Describe how the rules probability apply to genetics. (Use Punnett squares).
-Utilize the Belmonte-approved, 5-step method for solving genetics problems.
-Contrast and connect genotype and phenotype.
-Explain Mendel’s principle of independent assortment.
-Debate on the nature versus nurture conundrum.
-Predict the results of monohybrid crosses and use testcrosses to determine genotypes.
-Determine parental (P) traits by observing the traits of the F1 and F2 generations. 10.2
-Describe how alleles interact in intermediate inheritance.
–Describe inheritance patterns involving more than 2 (multiple) alleles.
-Explain how polygenic inheritance results in a wide range of phenotypes.
-Describe how environmental conditions can affect phenotypic expression. 10.3
-Summarize the chromosome theory of inheritance.
-Recognize and explain exceptions to Mendel’s principle of independent assortment.
-Understand how meiosis accounts for many of Mendel’s principles.
-Explain how crossing over generates new combinations of alleles.
-Understand how the probability of crossover between 2 genes depends on distance between them. 10.4
-Explain how sex-linked genes produce different inheritance patterns in males and females.
-Explain why sex-linked disorders are more common in males.
-Analyze and understand some of Morgan’s fruit fly crosses.
-Dominate all opposition in Get the Point!! 10.5
10.1 Mendel and Pea Plants
• Connect the concepts of
probability and randomness to
the study of heredity (genetics).
• Contrast the blending
hypothesis with the particulate
hypothesis of inheritance.
• Explore explanations of inheritance
that are not supported by
• Describe some of Mendel’s
procedures for his plant-breeding
The Blending Hypothesis
• For centuries, plant and animal
breeders had many questions about
the inheritance of flower colors, fur
length, and other characters of
organisms. Observations alone
could not answer all these
• Then an Austrian monk named
Gregor Mendel devised a series of
experiments that revealed the basic
rules underlying patterns of
• A trait is a variation of a
particular character. For
example, one plant might
have the trait of red flowers,
while another might have the
trait of yellow flowers.
• In the early 1800s, biologists
+ proposed the blending
hypothesis to explain
how offspring inherit traits
from both parents. For
example, suppose a red-
yields flowered plant were crossed
with a yellow-flowered plant
of the same species.
• According to the blending
hypothesis, the red and
yellow hereditary material in
the offspring would blend,
plants—like blending red and
yellow paint to make orange
paint. Based on this
hypothesis, all offspring of
orange-flowered plants would
also have orange flowers.
The Blending Hypothesis
(is not supported)
But people observed many exceptions to blending. For example, red-
flowered parents sometimes produced yellow-flowered offspring.
The blending hypothesis was eventually discarded because it could
not explain how traits that disappear in one generation can
reappear in later ones.
Mendel's Plant Breeding Experiments
• In the 19th century (1800’s), most
biologists worked by observing and
describing nature. Gregor Mendel was
one of the first to apply an experimental
approach to the question of inheritance.
His work eventually gave rise to
genetics, the study of heredity.
• For 7 years, Mendel bred pea plants and
recorded inheritance patterns in the
offspring. Based on his results, he
developed a particulate hypothesis of
• This hypothesis states that parents pass
on to their offspring separate and distinct
factors (today called genes) that are
responsible for inherited traits.
• Mendel stressed that these heritable
factors retain their identity generation Heredity/Inheritance
after generation. In other words, genes
are more like marbles of different colors
than paints. Just as marbles retain their How parents pass their
individual colors, genes retain their own
identities. traits to their offspring
Pea Plant Life Cycle
7 Pea Plant Traits studied by Mendel
• Mendel's 1st step was to identify pea plants that were true-
breeding. (When self-fertilized, a true-breeding or purebred plant
produces offspring identical in appearance to itself generation after
• For instance, Mendel identified a purple-flowered pea plant that,
when self-fertilized, always produced offspring plants that had
• To test the particulate hypothesis, Mendel crossed true-
breeding plants that had two distinct and contrasting traits—for
example, purple or white flowers. These contrasting pea varieties
served as parents for the next generation.
• In a method called cross-fertilization, or cross, sperm from the
pollen of one flower fertilizes the eggs in the flower of a different
plant. The fertilized eggs developed into embryos within seeds
(peas) that Mendel planted.
• The seeds grew into offspring that eventually produced their own
flowers. What color were their flowers?...Hmmmmm…
To prevent self-
1. Mendel snipped off all of the
anthers from the plant parent’s
(P) purple flower.
2. He then used a brush to snag
pollen from the other plant
parent’s white flower and
rubbed it on the sticky stigma
of the purple parent.
What color were the
progeny flowers from
• Mendel was a curious monk. He wondered, if a
purple-flowered pea plant were fertilized with
pollen from a white-flowered plant, what
color flowers would the offspring have?
10.1 Online Review
•Flower Parts/Pollination Activity 1, 2, 3, 4
•From Flowers to Fruits
•Genetics Timeline 1, 2, 3
•Genetics Timeline Activity
•Blending Hypothesis Overview 1, 2
•DNA From The Beginning
•Flower Quiz 1, 2, 3
•Pollination Quiz 1, 2
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