MENDELIAN GENETICS
AN INTRODUCTION TO HEREDITY
OBJECTIVES
• Demonstrate allele inheritance by drawing on prior
knowledge of natural selection.
• Be able to explain the basis behind Mendel’s first
law
GREGOR MENDEL
• 19th century (1800s)
• Austrian Monk who grew/studied peas
• No knowledge of chromosomes, nothing!
• Most thought babies were a mix of all of both parents
• Father of modern genetics!
• Genetics- study of inheritance and variation
PEA PLANT TRAITS
• Purple and White flower pea plants
• Single Gene (Ex- Color and Texture)
• Multiple genes (Most everything else)
• Purebred: homogenized Purple and White plants
• Bred many generations
SHOCKING RESULTS
• Initial Cross: Purebred Purple x Purebred White
What do you think the offspring (F1) looked like?
ALL PURPLE.
Where did the white go?
Breeding was a mix of the parents, right?
THE SECOND CROSSING
• Plants have male + female sex organs
• Allowed offspring (F1) to self-fertilize:
Purple + Purple
• What do you think he found?
• PURPLE AND WHITE FLOWERS (F2) in 3:1 ratio.
BUT HOW?!
CONCLUSIONS
• Law of Segregation- Mendel’s First Law
• Plants were inheriting 2 alleles from both parents
• Allele- variant of a gene
• Passing of which parental allele is completely random
• Published a paper on his work
• Do you think Mendel got the acknowledgement he deserved?
• No, of course not!
WHAT WAS THE KEY TAKE AWAY FROM MENDEL’S
FINDINGS?
Turn to a partner and discuss what you learned!