Genetics-Mendel-and-Punnett-Square-PowerPoint

Genetics: Mendel and Punnett Squares

Page 1: Introduction to Genetics

  • Focus on Mendel's experiments and Punnett Squares

Page 2: Gregor Mendel

  • Father of Modern Genetics

  • Conducted experiments on pea plants in monastery garden

  • Studied seven independent traits

  • Developed foundational principles of heredity and inheritance

  • Emphasized sexual reproduction, but acknowledged other types

Page 3: Reproduction Types

Asexual Reproduction

  • Offspring from one parent

  • Exact copies of that parent

  • Examples: Bacteria, some plants

Sexual Reproduction

  • Combines genetic information from two individuals

  • Leads to new individual

  • Examples: Humans, Horses

Page 4: Alleles

  • Offspring receive half genetic makeup from each parent

  • Genetic variations are called Alleles (a, b, c, d, e)

  • Each individual has two Alleles for each trait

  • Each parent contributes one Allele

Page 5: Dominant and Recessive Alleles

  • Alleles can be Dominant (e.g., E for brown eyes) or Recessive (e.g., e for blue eyes)

  • Dominant alleles expressed in offspring, recessive not

  • Example: Offspring with one E and one e will have brown eyes.

Page 6: Genotype vs Phenotype

  • Genotype: Genetic makeup (e.g., Ee)

  • Phenotype: Observable characteristics (e.g., brown eyes)

  • Genotype determines Phenotype

Page 7: Punnett Squares

  • Tool for calculating offspring genotype probabilities

  • Displays possible genotypes based on parent genotypes

Page 8: Constructing a Punnett Square

  • Place the alleles of the sire (e.g., Aa) on the top

  • Place the alleles of the dam (e.g., Aa) on the side

Page 9: Filling the Punnett Square

  • Fill in the squares with combined alleles

  • Designate combinations as Homozygous Dominant (AA), Homozygous Recessive (aa), or Heterozygous (Aa)

Page 10: Types of Alleles

Homozygous Alleles

  • Same alleles (e.g., AA or aa)

Heterozygous Alleles

  • One dominant, one recessive allele (e.g., Aa)

Page 11: Results from Punnett Squares

  • From example: 25% Homozygous Dominant (AA), 25% Homozygous Recessive (aa), 50% Heterozygous (Aa)

  • Total combinations always equal 100%

Page 12: Example 1 - Shackleford Stallion

  • Heterozygous stallion for brown eyes (Bb)

  • Homozygous recessive mare for blue eyes (bb)

  • Need to determine possible alleles and offspring

Page 13: Example 1 - Answer

  • Male alleles: Bb

  • Female alleles: bb

  • 50% offspring with brown eyes, 50% with blue eyes.

Page 14: Example 2 - Black Hair in Horses

  • Heterozygous black stallion breeds heterozygous black mare

  • Calculate probability of foal having black hair

Page 15: Example 2 - Answer

  • 75% chance foal will have black hair

  • Genotype distribution: 25% BB, 50% Bb, 25% bb.