Download Chapter 3 - Mendelian Genetics - HMartin

PowerPoint® Lecture Presentation for
Concepts of Genetics
Ninth Edition
Klug, Cummings, Spencer, Palladino
Chapter 3
Mendelian Genetics
Lectures by David Kass with contributions from
John C. Osterman.
Copyright
© 2009©Pearson
Education,
Inc.
Copyright
2009 Pearson
Education,
Inc.
Who Was Gregor Mendel?
nitro.biosci.arizona.edu
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Why the pea plant?
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90A1B-B2C5-4EB9-9C8AF39B7942A9FD/E532.jpg
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Mendel’s Pea Plant Traits
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Figure 3.1
Terms
• Homozygous vs. Heterozygous
• Genotype vs. Phenotype
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True-breeding
•
Plants homozygous for a characteristic are
true-breeding
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Monohybrid Cross
• involve a single pair of contrasting traits
• For ex. Flower color
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Genetic Cross
•
Parents used in a cross are part of the
parental generation (known as P)
•
Offspring of the P generation are
members of the first filial generation
(F1)
•
Offspring of the F1 generation are
members of the F2 generation, etc.
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• Mendel proposed the existence of
“particulate unit factors” for each trait.
• He suggested that these factors (now
called genes) and are passed unchanged
from generation to generation, determining
various traits expressed by each individual
plant.
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Self-fertilization
•
Pea flowers can self-fertilize
• Pollen from male structures transfers to
eggs in female structures
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Cross-fertilization
•
Mendel was able to
mate two different
plants by hand
(cross-fertilization)
• Female parts
(carpels) were
dusted with pollen
from other selected
plants
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Mendel’s 3 Postulates of Inheritance
• Unit factors exist in pairs
• In pair of unit factors for a single characteristic
in an individual:
• one unit factor is dominant and the other is
recessive
• Paired unit factors segregate (separate)
independently during gamete formation
• Law of Segregation
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Monohybrid
Cross
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Figure 3.2
Punnett Square
• Allows the genotypes and phenotypes
resulting from a cross to be visualized
easily (Figure 3.3).
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•Genotypic Ratio
&
•Phenotypic Ratio
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Figure 3.3
Testcross
• A way to determine
whether an
individual displaying
the dominant
phenotype is
homozygous or
heterozygous for
that trait (Figure
3.4).
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Dihybrid Cross
• Involves two pairs of contrasting traits
(Figure 3.5).
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Figure 3.7
Product Law
• Can be used to predict the frequency with
which two independent events will occur
simultaneously (Figure 3.6).
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Mendel’s Fourth Postulate
• Mendel’s fourth postulate states that:
• Traits assort independently during gamete
formation
• Law of independent assortment
• All possible combinations of gametes will form
with equal frequency.
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Testcrosses
• Testcrosses can also be used with two
independent traits (Figure 3.8).
• G?W? X ggww
• (G=yellow; g=green; W=round; w=wrinkled)
• What will the expected phenotypic ratios be
for the above testcross?
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Figure 3.8
Trihybrid Crosses
• Trihybrid crosses involving 3
independent traits show that Mendel’s
rules apply to any number of traits.
• The forked-line (branched diagram) method
is easier to use than a Punnett square for
analysis of inheritance of larger number of
traits (Figure 3.10).
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Figure 3.10
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Table 3.1
3 of Mendel’s
postulates and their
basis in chromosomal
segregation during
meiosis are shown in
Figure 3.11.
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Figure 3.11
Laws of Probability Help to Explain
Genetic Events
•
•
•
•
Product Law
Sum Law
Conditional Probability
Binomial Theorem
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Chi-Square Analysis Evaluates the
Influence of Chance on Genetic Data
• Chance deviation from an expected
outcome is diminished by larger sample
size.
• Null hypothesis
• Chi-square (2) analysis is used to test
how well the data fit the null hypothesis.
• Х2 =Ʃ (O-E)2
E
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Table 3.3
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Figure 3.12
Pedigrees Reveal Patterns of
Inheritance of Human Traits
• A pedigree shows a family tree with
respect to a given trait. Pedigree analysis
reveals patterns of inheritance.
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Figure 3.13
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Figure 3.14
The End
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