observing patterns in inherited traits -...
TRANSCRIPT
© Cengage Learning 2015
Biology Concepts and Applications | 9e
Starr | Evers | Starr
© Cengage Learning 2015
Chapter 13 Part 2
Observing Patterns in
Inherited Traits
Monohybrid Cross Practice #1
• A pea plant produces yellow peas and has the genotype of YY is crossed with a pea plant that produces green peas and has the genotype of yy.
– Draw a Punnett square of this cross. What are the predicted genotype and phenotype ratios of this cross?
• The F1 offspring of this cross are then crossed to each other.
– Draw a Punnett square of this cross. What are the predicted genotype and phenotype ratios of this cross?
Mendel’s Next Question: • What happens to the inheritance of two
different traits in the same cross?
Figure 9.4
Dominant Recessive
White
Pod shape Inflated Constricted
Flower position
Pod Color
Dominant Recessive
Flower color Purple
Axial Terminal
Green Yellow
Tall Dwarf
Seed shape Round Wrinkled
Seed color Yellow Green Stem length
Dihybrid
Crosses &
Independent
Assortment
Figure 13-8 p211
meiosis II
meiosis I
gamete genotype:
meiosis II
meiosis I
or
Pt pT PT pt
Independent
Assortment
Figure 13-10a p212
Other types of inheritance patterns: Incomplete Dominance in Snapdragons
Red x White = Pink
Codominance
• Both alleles are dominant in the heterozygote
• Blood typing as an example
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Pleiotropy – A single gene affects multiple traits
Example: Sickle cell disease
Individual homozygous
for sickle-cell allele
Sickle-cell (abnormal) hemoglobin
Abnormal hemoglobin crystallizes into long, flexible chains,
causing red blood cells to become sickle-shaped.
Sickled cells can lead to a cascade of symptoms, such as
weakness, pain, organ damage, and paralysis.
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Epistasis (Polygenic Inheritance) More than one gene acts on a single trait
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Does the environment affect phenotype?
“Nature vs. Nurture”