Heredity

1
Heredity

• Ch. 5

2
Objectives

• Explain the relationship between traits and
  heredity
• Describe the experiments of Gregor Mendel
• Explain the difference between dominant and
  recessive traits

3
Terms

• Heredity
• Dominant Trait
• Recessive Trait

4
Mendel and His Peas

• Heredity the passing of traits from parents to
  offspring
• Ex. Hair color, eye color

5
Gregor Mendel

• Austrian
• Entered a monastery at 21
• Received training in teaching in Vienna, Austria
• Discovered the principles of heredity
• Worked with plants (peas)
• Grow quickly
• Many kinds available
• Able to self-pollinate

6
Self-Pollinating Peas

• Male and Female Reproductive structures
• Male Anther, Pollen (sperm)
• Female Stigma, ovary (eggs)
• Why do plants have flowers?

7
True-Breeding Plant

• When a Self-Pollinating plants offspring all
  have the same trait as the parent
• A plant with purple flowers will always produce
  other plants with purple flowers

8
Cross-Pollination

• Pollen from one plant fertilizes the ovule of a
  flower on a different plant
• Carried by insects, wind

9
Characteristic and Traits

• Characteristic A feature that has different
  forms in a population
• Ex. Hair color
• Trait the different forms of a characteristic
• Ex. Brown hair or blonde hair
• Mendels Peas- used purple and white flowers

10
Mix and Match

• Mendel used true breeding plants (would know what
  to expect)
• He crossed (breed) two plants with different
  traits of one characteristic
• He wanted them to cross-pollinate so he removed
  the anthers of one so that it could not self
  pollinate

11
Mendels First Experiment

• Crossed pea plants (7 characteristics)
• True-breeding
• Crossed purple flowers and white flowers
• The offspring from the first cross is the First
  generation plant
• All had purple flowers
• Dominant Trait trait observed in the first
  generation when parents that had different traits
  (purple and white) were bred
• Recessive Trait trait that reappears in the
  second generation after disappearing in the first
  generation when parents with different traits are
  bred

12
Mendels Second Experiment

• Allowed first generation plants to self-pollinate
• White flowers appeared in the second generation

13
Ratios in Mendels Experiments

• Counted the number of plants with each trait in
  the second generation (Table 1 pg 118)
• Recessive trait did not show up as often as the
  dominant
• Ratio a relationship between two different
  numbers that is often expressed as a fraction