Ch. 13 Mendel and Heredity

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Ch. 13 Mendel and Heredity

• When we think of how offspring resemble or differ
  from their parents, we refer to specific traits.

• Traits are distinguishing characteristics

• Such as

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Mendel and Heredity

• What differences among these people do you see?
• Genetics is the branch of biology that seeks to
  explain inherited variation.

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Variations make each individual unique

• Inherited features are the building blocks of
  evolution.
• Remember that crossing over adds to the genetic
  variety of the gametes.
• Environment also plays a role in shaping
  variation.
• Nutrition
• Temperature
• Sun exposure

• The search for explanations
• lies within
• chromosomes, genes nucleic acids.

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Heredity and Environment

• Studying twins has helped separate the effects of
  inheritance and the environment.
• Ex weight and intelligence are affected by
  environment also coat color in certain
• mammals
• Explanations of Heredity

New Theory Genetics
Old Theory Blending
Could not explain why some individuals resemble
other relatives.
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How do we know that all traits do not come from
the blending of our parents traits?
Gregor Mendel He was a monk, gardener, science
teacher, mathematician

• Experiment
• Gregor Mendel used garden peas.
• He developed the fundamental principles of
  heredity that became the foundation of modern
  genetics
• Why did he choose peas?

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Mendel's Pea Plant
A
B
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Effects of environment on Twins
Twin on right spent decades sunbathing and
smoking while sister did not.
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Heredity and Environment
Siamese cats have a gene for dark fur, but the
enzyme produced by the gene functions best at low
temperatures. The cats extremitiesits ears,
paws, and tailare cooler than the rest of its
body.
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Why Mendel chose peas?

• 1)Easy to grow
• 2)Reproduce quickly
• 3)Study many generations
• 4)Both male and female parts
• 5)Control how they mate
• (Self-fertilizing)
• 6)Can make a purebred line