Mendelian Inheritance Quiz

Course Contents

• Classical Genetics
• Mendelian Inheritance
  • Mendel's experiments
  • Types of dominance

Lecture Objectives

• Mendelian Inheritance

Key Concept

• Traits are inherited as discrete units

Overview: Drawing from the Deck of Genes

• The "blending" hypothesis suggests that genetic material from parents blends together
• The "particulate" hypothesis suggests that parents pass on discrete heritable units called genes

Gregor Johann Mendel (1822-1884)

• "Father of Genetics"
• Austrian monk and scientist
• His work was not recognized until the 20th century

Gregor Johann Mendel

• Laid the groundwork for genetics in the 1860s
• Deduced the principles of genetics by breeding garden peas
• Relied upon mathematics, physics, and chemistry
• Died in 1884.
• Work was rediscovered in 1900 by Hugo de Vries and others

Mendel Laid the Groundwork for Genetics

• Traits are distinguishing characteristics that are inherited
• Genetics is the study of biological inheritance patterns and variations
• Mendel showed that traits are inherited as discrete units

Mendel’s data revealed patterns of inheritance

• Mendel made three key decisions:
  • Use of purebred plants.
  • Control over breeding.
  • Observation of seven "either-or" traits.

Pea plants were a good choice to study - due to:

• Self-pollinating
• True-breeding - offspring are identical to parents
• Can be grown in a small area
• Produce many offspring
• Can be artificially cross-pollinated
• Many traits known
• Easy to grow

Generations of Traits

• True-breeding parental generation is called the "P generation".
• The offspring of the two parental plants is called the "F1 generation".
• A cross between the F1 generation is called the "F2 generation".

Mendel's Pea Plant Experiments

• Used pollen to fertilize selected pea plants
• Prevented self-fertilization by cutting off immature stamens
• Dusted carpel with pollen from another plant to cross- fertilize
• The carpel develops into a pod, containing seeds that are then planted

Mendel Used Pollen to Fertilize Selected Pea Plants

• True-breeding parents are called the "P" generation
• Hybrid offspring are called the "F1" generation
• When F1 individuals self-pollinate or cross-pollinate, the "F2" generation is produced

Mendel Controlled the Fertilization of His Pea Plants

• Removed male parts (stamen) of pea plants
• Fertilized the female part (pistil) with pollen from a different plant
• Allowed the resulting plants to self-pollinate

Mendel's Pea Plant Experiments

• All plants in F1 generation had purple flowers
• F1 plants are all heterozygous
• Some plants in F2 generation had purple flowers and some had white flowers

Seven Pea Plant Characters Studied by Mendel

• Flower color: Purple (dominant) or White (recessive)
• Flower position: Axial (dominant) or Terminal (recessive)
• Seed color: Yellow (dominant) or Green (recessive)
• Seed shape: Round (dominant) or Wrinkled (recessive)
• Pod shape: Inflated (dominant) or Constricted (recessive)
• Pod color: Green (dominant) or Yellow (recessive)
• Stem length: Tall (dominant) or Dwarf (recessive)

Key Concept

• The inheritance of traits follows the rules of probability

Punnett Squares Illustrate Genetic Crosses

• A grid system for predicting all possible genotypes resulting from a cross
• Axes represent possible gametes of each parent
• Boxes show possible genotypes of the offspring
• Punnett Square yields a ratio of possible genotypes and phenotypes

How to Use a Punnett Square

• Take the letter from the top, combine it with the letter from the left, and write the result in the box

How to Use a Punnett Square (Cont.)

• Heterozygous red flower (Rr) crossed with homozygous white flower (rr)
• Write one parent on top, and the other on the left side of the square

How to Use a Punnett Square (Cont.)

• Write genotypes of the offspring to find genotype probability
• Each box represents 25%
• Rr 2/4 or 50%
• rr 2/4 or 50%

How to Use a Punnett Square (Cont.)

• Write the phenotypes of the offspring to find phenotype probability

Test your knowledge on Mendelian inheritance and the foundational experiments conducted by Gregor Mendel. This quiz includes questions about traits, dominance, and the 'particulate' versus 'blending' hypotheses in genetics. Perfect for students studying classical genetics concepts!